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Speaker 1: Howdy extraordinaries. Today we're discussing human lice. If you're a parent,

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Speaker 1: you may be at the stage in your life where

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Speaker 1: you're worried about kids bringing home lice from school. But

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Speaker 1: back in your wilder days, if you had wilder days,

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Speaker 1: there may have been another kind of lice found out

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Speaker 1: a different part of the body that you worried about.

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Speaker 1: Maybe it made you feel let's say, crabby. We're talking

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Speaker 1: about both kinds of lice today and some historically catastrophic

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Speaker 1: diseases that lice frequently caused in the past. So decide

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Speaker 1: if this episode is appropriate for you or young ears

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Speaker 1: that might also be listening. Thanks When you grab a

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Speaker 1: lice comb and spend hours picking through your kid's hair

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Speaker 1: to remove those little buggers, you're engaging in a time

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Speaker 1: honored human tradition that stretches for millennia. Direct evidence of

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Speaker 1: human head lice goes back ten thousand years, and we

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Speaker 1: found six five hundred year old head lice combs in Egypt.

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Speaker 1: But we've probably had head lice even earlier than that,

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Speaker 1: perhaps even since the dawn of our species. So if

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Speaker 1: this pest has been with us during our entire journey

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Speaker 1: as a species, Then can studying it tell us anything

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Speaker 1: about our past? Or can studying it at least tell

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Speaker 1: us how to get rid of it better? Welcome to

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Speaker 1: Daniel and Kelly's lousy universe.

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Speaker 2: Hi. I'm Daniel. I'm a particle physicist who likes to

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Speaker 2: think about aliens, and my family's had lice more times

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Speaker 2: than I can count.

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Speaker 3: Hello. I'm Kelly Waiter Smith.

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Speaker 1: I study parasites and and my family has never had lice.

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Speaker 2: But we have had fleas, not even once in a

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Speaker 2: life's time.

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Speaker 3: Nahaa, what a lousy joke.

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Speaker 2: It's not even my joke. It's literally the name of

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Speaker 2: the place we took our kids to get them de loused.

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Speaker 1: Oh man, you know, I don't know how we avoided

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Speaker 1: it because my daughter like puts on other people's hats

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Speaker 1: and like, well, you know, she'll be like, oh yeah,

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Speaker 1: I was like, your hair looks brushed?

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Speaker 3: How did that happen?

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Speaker 1: And she's like, oh, I bird a friend's brush at school,

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Speaker 1: And I'm like, God, somehow we have managed to completely

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Speaker 1: avoid lice. I don't know how. It blows my mind.

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Speaker 2: Maybe something about your remote living on your enclave, escaping humanity, you.

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Speaker 3: Know, Yeah, but I don't know.

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Speaker 1: She still goes to school where they like, I don't know,

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Speaker 1: it's swhear they greet each other by like licking each

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Speaker 1: other's hands and then rubbing their heads together, Like kids

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Speaker 1: are weird and gross.

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Speaker 2: Well, I was going to ask you about whether your

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Speaker 2: family had lice, but now I want to hear all

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Speaker 2: about how you got fleas. Which animal on the farm

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Speaker 2: passed them to you.

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Speaker 3: Oh, this was when we lived in a city. This

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Speaker 3: blew my mind.

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Speaker 1: Okay, So we lived in Houston and we had two cats,

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Speaker 1: and we had just had our second baby. Our second

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Speaker 1: baby just came home, so we were like out of

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Speaker 1: our minds with like exhaustion and like you know, the

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Speaker 1: delirium that comes along with having a new baby at home.

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Speaker 1: And it was winter, and so I forgot to give

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Speaker 1: our cats their flea medication. But they're one hundred percent

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Speaker 1: indoor cats.

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Speaker 3: And it was winter, so it was.

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Speaker 2: Like winter in Houston.

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Speaker 3: Winter in Houston. Yeah, winter in Houston.

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Speaker 2: So what's the relevance of winter, I'm not following.

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Speaker 1: I think there's fewer fleas outside in the winter. I

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Speaker 1: don't know.

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Speaker 2: I probably fleas all migrate to Mexico in the winter.

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Speaker 3: Or something yes, no, no, I guess I don't know

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Speaker 3: much about fleas.

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Speaker 1: But somehow, in my head it's less likely that someone's

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Speaker 1: gonna walk around in the grass and bring a flea

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Speaker 1: that could infect a cat back into your house or something,

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Speaker 1: and then they're gonna find your cat anyway. Somehow, Well,

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Speaker 1: my one hundred percent indoor cats got fleas, and I

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Speaker 1: didn't realize it until I was changing a diaper and

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Speaker 1: I saw something hop wow, and there was a flea

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Speaker 1: on my kid. And I was like, I am the

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Speaker 1: worst mother in the whole world, and so immediately you're not.

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Speaker 2: But that doesn't nominate you for being the best money.

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Speaker 3: That was an emotional roller coaster there. I felt a

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Speaker 3: little better, and then I felt real bad again.

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Speaker 2: And so it's hard to compliment somebody for having fleas

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Speaker 2: on their babies.

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Speaker 3: You didn't have to like rank me at all.

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Speaker 1: I could just tell the story and anyway, well, your

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Speaker 1: family has had life an uncountable number of times.

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Speaker 3: So I don't think either one of us are winning

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Speaker 3: parents of the Year.

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Speaker 2: I'm not suggesting it's like seventeen thousand. I'm just saying

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Speaker 2: it's often enough that I didn't even keep track it's

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Speaker 2: like two or three times. I'm not even sure. It

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Speaker 2: just felt like a routine. I remember going back to

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Speaker 2: once in a Lifetime and being like, I thought we

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Speaker 2: were supposed to only be here once in a lifetime.

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Speaker 1: Well, that's false advertising, because you can get lice over

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Speaker 1: and over and over again.

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Speaker 2: That's true. But I do love how this whole field

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Speaker 2: is riddled with terrible puns.

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Speaker 1: Yeah yeah, well, and I think from lice come many

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Speaker 1: words like nitpicking. Oh yeah, I mean we've had, you know,

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Speaker 1: like the Bible has stories about lice as a plague

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Speaker 1: like it.

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Speaker 3: This has been part of our history for a really.

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Speaker 1: Long time, you know, Like we find evidence of lice

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Speaker 1: on mummies, which is amazing because lace shouldn't preserve well, right,

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Speaker 1: So the fact that you find any of them probably

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Speaker 1: means there were loads of them.

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Speaker 2: Are they also individually wrapped in little mummy cloths? Ah?

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Speaker 1: No, no, because nobody was trying to bring them with

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Speaker 1: them into the afterlife. But but there's an old document

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Speaker 1: called the Papyrus Ebers that's like, you know, an ancient

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Speaker 1: Egyptian document that has a recipe for how.

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Speaker 3: To make like a thing to kill lice.

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Speaker 1: And so we've We've been dealing with this for a

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Speaker 1: long time, probably from like literally.

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Speaker 3: The beginning of our species, which we're gonna get to interesting.

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Speaker 2: Well, I've had my own personal evolution with my feelings

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Speaker 2: about life because I used to feel like, oh my god,

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Speaker 2: that is the creepiest thing. You have, these little animals.

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Speaker 2: They're crawling all over you. They're like mating and pooping

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Speaker 2: and doing all this stuff. Yuck. But you know, then

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Speaker 2: I'm at Katrina and I got married to her, and

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Speaker 2: now I fully understand that every surface of my body

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Speaker 2: is a little ecosystem and I'm always going to be

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Speaker 2: covered in little critters, little microbes doing this that and

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Speaker 2: the other. And lice are just you know, they're like

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Speaker 2: the elephants in that forest, and like whatever.

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Speaker 1: Man, I totally disagree with you, but I don't want

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Speaker 1: I don't want to dissuade you from this story.

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Speaker 3: You've told yourself to make yourself feel better. So I

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Speaker 3: think we should move on to the question that prompted

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Speaker 3: in this episode.

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Speaker 2: Let's not dig into dangel psychological issues. Let's answer questions

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Speaker 2: from listeners. So, Kelly, why are we talking about life today?

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Speaker 1: Well, we have this amazing discord community and You can

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Speaker 1: join us by going to Daniel and Kelly dot org

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Speaker 1: and clicking on the link to join our discord community.

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Speaker 1: And in Discord, user Bauer family told this story that

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Speaker 1: they sort of vaguely remembered about how the divergence time

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Speaker 1: between pubic lice and head lice can tell you about

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Speaker 1: when we became hairless, because when we lost the hair

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Speaker 1: on you know, like our bellies and our shoulders or whatever,

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Speaker 1: there now was like a big gulf between you know,

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Speaker 1: any lice that are in your hair and any lice

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Speaker 1: that are in your pubic region. And actually the hair

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Speaker 1: in your pubic region is quite different in like texture

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Speaker 1: and thickness and stuff than the hair on your head.

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Speaker 1: And so the idea here is if you could date

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Speaker 1: the divergence between those two life species, you can figure

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Speaker 1: out when humans became mostly hairless.

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Speaker 2: This is like having a population of animals on some

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Speaker 2: continent and then it splits into two and you can

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Speaker 2: track them individually exactly.

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Speaker 3: Yes.

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Speaker 1: Allopatrick's speciation is when you get like a physical barrier

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Speaker 1: between what was once one population. Now it becomes too

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Speaker 1: and over time they separate enough that they become different species,

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Speaker 1: and you know, maybe can't even breed together anymore. Wow,

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Speaker 1: So this was like a story that they had heard

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Speaker 1: and they wanted to know more.

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Speaker 3: It's totally wrong, which we're gonna get totally.

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Speaker 4: Wrong, totally wrong.

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Speaker 2: It sounds like such a cool science story. And I

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Speaker 2: was going to make all these jokes about pubic island.

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Speaker 1: Well you still can't, because we're gonna still talk about

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Speaker 1: pubic lice.

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Speaker 3: And they're interesting, but yet, like.

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Speaker 1: In general, as I was going through and doing the research,

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Speaker 1: I realized they were all of these things I had

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Speaker 1: heard about lice that when you dig into the research,

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Speaker 1: are totally not substantiated by the science. And so we

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Speaker 1: are going to be dispelling lousy stories today on DKA.

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Speaker 2: Well is this going to be a wet blanket episode

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Speaker 2: or are we going to come away with an even

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Speaker 2: more interesting, actually substantiated science story.

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Speaker 1: Yeah, those things are not mutually exclusive, so we're going

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Speaker 1: to do both.

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Speaker 2: So let's dig into it. Start us off with an

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Speaker 2: introduction to lice, because I think I have this idea

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Speaker 2: that lice are these basically tiny, little crawling critters, maybe

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Speaker 2: like a shrunken down version of a beetle that's living

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Speaker 2: on me.

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Speaker 3: Yes, so they don't have wings.

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Speaker 1: They can only like crawl, So fleas can jump, but

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Speaker 1: lice can only crawl. They're very slow moving, so pretty

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Speaker 1: much the only way they get from one host to

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Speaker 1: another is like physical contact, and so you need to

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Speaker 1: like maybe one get stuck in a hat and then

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Speaker 1: you put that hat on your head and now it

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Speaker 1: is on you. But they're not jumping from host to hosts.

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Speaker 2: And so how big are these things?

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Speaker 1: They're about the size of like a sesame seed or

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Speaker 1: a pencil tip, so they're tiny.

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Speaker 2: Oh oh, that's actually bigger than I thought. I thought

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Speaker 2: they're gonna be almost impossible to see.

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Speaker 1: No, no, no, I mean, I guess you offloaded the

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Speaker 1: job of nit picking your kids to once upon a

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Speaker 1: lice what was it, once in a lice time? Lots

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Speaker 1: of free advertising for once in a lifetime today.

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Speaker 3: But if you take like, you.

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Speaker 1: Know, a lice comb and you go through, you can see,

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Speaker 1: especially if you have dark hair. Yeah, you can see

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Speaker 1: the eggs which are even smaller, and then you can

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Speaker 1: see the adults and you can, you know, get them

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Speaker 1: out with a lice comb.

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Speaker 2: I see. And are these guys insects or are they

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Speaker 2: arthropods or something else? Like if you made this thing

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Speaker 2: like the size of a football, what would it look like?

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Speaker 1: Okay, so that they are arthropods and their insects, and

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Speaker 1: if you zoomed in so their bodies, you know, there's

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Speaker 1: like I think something like five thousand species of like

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Speaker 1: what you would maybe count as lice, but like for

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Speaker 1: human lice, you know, their bodies are some of them

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Speaker 1: kind of look football shaped the like base part of

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Speaker 1: their body, although pubic lice tend to be a little

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Speaker 1: bit more like flattened. But anyway, and then they've got

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Speaker 1: six appendages that stick out, and they've got sort of

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Speaker 1: like hooky hands that they used to like cling to

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Speaker 1: your hair to like hug your hair or hold onto it,

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Speaker 1: sort of like the way a sloth holds onto like

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Speaker 1: a tree branch. And then they've got like heads with antenna.

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Speaker 1: And they look pretty clear ish or like orange y

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Speaker 1: ish most of the time, unless they've got some a

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Speaker 1: blood meal, then they can be kind of red.

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Speaker 2: So do they look like tiny ticks basically ticks?

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Speaker 1: How would I say they're different? So the tick body

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Speaker 1: tends to be like more smooth, whereas a lice body

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Speaker 1: looks a little bit more like ridged to me.

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Speaker 2: All right, but they're tiny, little creepy crawlies. Yeah, And

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Speaker 2: you said something fascinating. You said, there's thousands of species

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Speaker 2: of lice, but not all of them are human lice.

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Speaker 2: How many species are there of human lice?

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Speaker 1: So there's two species of lice that you commonly find

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Speaker 1: on humans, and that's the head slash body louse. And

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Speaker 1: we're gonna spend a lot of time talking about that

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Speaker 1: slash a little bit later. It's a very important slash, okay.

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Speaker 2: But the different species of lice are connected to the

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Speaker 2: different species of a host's right, So like, yes, chimp

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Speaker 2: lice is different from human lice, is different from dog lice.

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Speaker 2: So I'm not gonna get lice from my dog, and

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Speaker 2: you weren't going to get lice from your cat.

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Speaker 3: That's right.

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Speaker 1: Well, so what the cat story? Those were fleas, right,

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Speaker 1: very different diferent. Actually, I know they don't sound different,

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Speaker 1: but like the fact that they can hop, I mean

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Speaker 1: their legs are like totally different.

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Speaker 2: I know, I remember the fleas and lice are different.

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Speaker 2: But I was making the point that, like, if your

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Speaker 2: cat had fleas and lice, you could get its fleas,

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Speaker 2: but not.

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Speaker 1: It's lyce yeah, yeah, we got their fleas, but if

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Speaker 1: they had had lice, we wouldn't have gotten their lice.

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Speaker 1: Yeah yeah, yeah, So lice tend to be very very

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Speaker 1: host specific, and you tend to find lice in two

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Speaker 1: different flavors.

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Speaker 3: It is the gross way of.

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Speaker 1: Saying that there are scavenger lice, which eat like dead

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Speaker 1: skin pieces and stuff. We don't have those kinds of

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Speaker 1: lice on human bodies, unfortunately, because what we have are

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Speaker 1: the sucking lice, which have like a thing that they

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Speaker 1: shove into your body so that they can suck blood.

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Speaker 3: And yeah, they're like feeding on blood.

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Speaker 2: So they're like crawling mosquitoes.

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Speaker 3: Yeah, they're like crawling mosquitos. But whereas mosquitoes.

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Speaker 1: Might take blood meals from multiple different people, your lice

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Speaker 1: are probably spending most of their life on you, unless

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Speaker 1: they jump to a partner that you have.

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Speaker 2: Well, I still prefer lice because mosquito leave you with

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Speaker 2: these itchy bites, and I'm always like, just take the

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Speaker 2: blood meal, don't leave me with the bite. Okay, But

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Speaker 2: but lyce don't give you itchy bites, do they?

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Speaker 3: Oh heck yeah they do.

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Speaker 1: Yeah, So okay, so life's bite and depending on how

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Speaker 1: your body responds to them, which is the same thing

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Speaker 1: with mosquitoes. You can get itchy, and in fact, for

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Speaker 1: head lice, like the biggest thing you worry about is

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Speaker 1: that somebody is going to scratchcratch, cratchratch, scratch, and then

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Speaker 1: get a secondary bacterial infection. And so it's not that

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Speaker 1: the lice are giving you a disease, but if you

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Speaker 1: like create a bunch of wounds on your head from

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Speaker 1: scratching and then bacteria gets in there, that could cause

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Speaker 1: its own problem.

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Speaker 4: Right.

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Speaker 2: Of course, having an itchy head is one of the

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Speaker 2: biggest clues that you might have lice.

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Speaker 1: Of course, yes, yeah, right, And so where is a

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Speaker 1: mosquito takes a blood meal from you and then goes

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Speaker 1: and lays her eggs somewhere else. Lice take a blood

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Speaker 1: meal from you and then they cement their eggs.

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Speaker 3: This is for head lice.

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Speaker 1: They cement their eggs to your hair and they stay

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Speaker 1: with you and then they hatch, and so you have

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Speaker 1: a population that, if you don't do anything about it,

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Speaker 1: over time, can multiply and become huge. Whereas one mosquito

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Speaker 1: bites you, they go away, maybe their kids will never

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Speaker 1: bite you. And so I think I'd rather have a

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Speaker 1: mosquito bite than a lice that might turn into a

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Speaker 1: community of lice wiener smith manor up there or something.

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Speaker 2: They got their own little farm. So, if every species

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Speaker 2: of animal has their own species of lice, and some

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Speaker 2: of these species have common ancestry, did the louse species

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Speaker 2: diverted at the same time as the hosts? How did

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Speaker 2: that work?

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Speaker 4: Yes?

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Speaker 1: Okay, so this is this is where we get into

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Speaker 1: like the fascinating evolutionary biology. Okay, So we have two

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Speaker 1: different species of lice on our body, which we've talked about.

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Speaker 1: Our head lice share a common ancestor with the lice

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Speaker 1: that you find on chimpanzees. So what that means is

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Speaker 1: about six million years ago we shared a common ancestor

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Speaker 1: with chimpanzees. When we split, both of those groups that

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Speaker 1: split had lice on them, and so over time, the

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Speaker 1: lice on chimps ended up evolving into like the chimp louse,

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Speaker 1: and the louse that was on you know what ended

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Speaker 1: up becoming humans or Homo sapiens evolved into pendiculous humanas so,

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Speaker 1: which is our human louse. And so the common ancestor

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Speaker 1: for those lice is from six million years ago, which

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Speaker 1: is about when chimpanzees and humans split.

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Speaker 3: Does that make sense?

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Speaker 2: All right, So chimps and humans split almost six million

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Speaker 2: years ago, and human head lice and chimp lice split

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Speaker 2: around the same time.

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Speaker 4: Yes, okay, right, I'm with you so far.

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Speaker 2: But there's another species of lice on humans, and we

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Speaker 2: haven't explained yet where that came from.

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Speaker 1: That's right, And I think I want to stay on

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Speaker 1: the head lice for a second and talk about what

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Speaker 1: headlights can tell us about human evolution.

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Speaker 3: But we will be back to the pubic lice, don't

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Speaker 3: you worry.

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Speaker 2: We will be visiting Pubic Island very shortly. But right

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Speaker 2: now we're staying on the continent of the head.

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Speaker 4: Okay, okay.

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Speaker 1: So when you look at the head lice, and you

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Speaker 1: collect head lice from all over the world, you see

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Speaker 1: something kind of weird, which is that they're seeing to

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Speaker 1: be something like five or six of what they call clades,

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Speaker 1: which is to say, if you look at them genetically,

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Speaker 1: you're like, oh, the lice over here, they're really closely related.

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Speaker 1: But the lice over here they look different. They're not

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Speaker 1: as closely related, they're not a different species. But what

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Speaker 1: we think was happening was that, Okay, chimpanzees and humans split,

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Speaker 1: but it's not like it's a straight line to Homo sapiens. Right,

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Speaker 1: there was Homo erectus and Neanderthals and Denisovans, and it

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Speaker 1: was really fun reading papers from before we had definitive

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Speaker 1: evidence that Neanderthals and Denisovans bread and so folks might

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Speaker 1: remember we had Nathan Lentz on the show to talk

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Speaker 1: about how we know from genetic evidence that humans were

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Speaker 1: breeding with Neanderthals, But what they think happened is that

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Speaker 1: like Neanderthals and homoerectus and Denisovans, they all had their

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Speaker 1: own lice, and for the most part, those lice were separated,

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Speaker 1: so they were starting to become different species. So there

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Speaker 1: was starting to become like a Neanderthal lice and a

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Speaker 1: Denisovan lice.

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Speaker 2: So the life's populations were drifting apart, the same way

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Speaker 2: the human populations were, but they weren't yet so far

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Speaker 2: apart they couldn't.

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Speaker 4: Interbreed exactly, right.

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Speaker 1: But then Homo sapiens started breeding with these other humans,

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Speaker 1: which we know happened, right, And so we think that

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Speaker 1: some of these clades are actually like the Neanderthal lice

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Speaker 1: jumping ship while the Neanderthals are going extinct, and so

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Speaker 1: like some of our clades might have come from like

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Speaker 1: Homo erectus, who were going extinct and we got them

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Speaker 1: when we like, you know, we're sharing a bed together

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Speaker 1: probably or I don't know, sharing hats.

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Speaker 3: Who knows if we had hats back then.

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Speaker 1: But so there's evidence in like the different clades of

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Speaker 1: headlicce that you find around the world of the different

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Speaker 1: kinds of species of humans that we sort of interacted

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Speaker 1: with in our past.

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Speaker 2: That's incredible. So we see evidence for human divergence and

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Speaker 2: recombination in our own genetic heritage and that's mirrored in

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Speaker 2: the lice. That's incredible.

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Speaker 1: Yeah, right, So I've seen papers that are claiming that

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Speaker 1: lice can teach us about human evolution. As far as

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Speaker 1: I can tell, head lice have been able to provide

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Speaker 1: additional support for what we already think is happening about

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Speaker 1: human evolution. But there's been nothing in the head lice

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Speaker 1: where we've seen something here and been like that definitely

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Speaker 1: means that humans must have done this, and then later

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Speaker 1: we found archaeological evidence for it. But still it's nice

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Speaker 1: because like, you know, you have data from one source,

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Speaker 1: and you feel much better if you have data from

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Speaker 1: a completely different source that's saying the same thing. And

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Speaker 1: so human head lice are helping us feel more confident

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Speaker 1: about these stories about like when our ancestors left Africa

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Speaker 1: and when we came back together again, and anyway, I

390
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Speaker 1: think that's pretty awesome.

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Speaker 2: Absolutely, and it's an important part of doing science.

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Speaker 1: Right.

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Speaker 2: You get a story from one place, you want to

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Speaker 2: see if another line of data tells the same story

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Speaker 2: or a different story, and if it's different, why is that?

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Speaker 2: And then there's a mystery to untangle. So it's always

397
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Speaker 2: good to check things in different directions and if they

398
00:18:57,119 --> 00:18:58,800
Speaker 2: line up and tell the same story, then yeah, you're

399
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Speaker 2: more confident in it. Though of course you could always

400
00:19:01,320 --> 00:19:03,680
Speaker 2: learn new stuff, that's right, So that's very cool.

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Speaker 1: Yeah yeah, Okay, So now let's take a break and

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Speaker 1: when we come back, we're going to go down under.

403
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Speaker 1: Sorry Australians, croy.

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Speaker 3: All right, we're back and we are moving from the

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Speaker 3: head to the pubic lice.

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Speaker 1: So this is where we are really digging into the

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Speaker 1: question from the listener. So the hypothesis here is that, okay,

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Speaker 1: we got our head lights from this common ancestor, and

409
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Speaker 1: then we went off being humans, and over time the

410
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Speaker 1: population of lice that we're living on us split into

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Speaker 1: two different islands, the hair that we have on our

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Speaker 1: head and then the hair that we have in our

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Speaker 1: pubic region. And that if you can date when that

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Speaker 1: split happened, that must tell you when we lost the

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Speaker 1: hair around like the middle part of our body.

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Speaker 2: Right, although not all of us are hairless in the

417
00:20:10,760 --> 00:20:13,119
Speaker 2: middle part of their body, right, you know, for some

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Speaker 2: of us, you could even say that there's a continuous,

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Speaker 2: you know, land bridge there from one kind of hair

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Speaker 2: to the other. Does this hypothesis rely on there being

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Speaker 2: like a really distinct break there.

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Speaker 1: Well, so that is not where things fall apart. But

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Speaker 1: that is a good point. And another point is that,

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Speaker 1: you know, which we've already mentioned, is that the hair

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Speaker 1: in those two different locations has very different thickness and consistency,

426
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Speaker 1: and so you find different grasping hands on the different

427
00:20:43,680 --> 00:20:45,679
Speaker 1: lice in the different regions because you sort of just

428
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Speaker 1: need different grappling hooks depending on where you're living. But

429
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Speaker 1: what's better evidence is the fact that actually your pubic

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Speaker 1: lice are not the direct ancestors of your head lice.

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Speaker 3: They are lice that we got, not.

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Speaker 1: From a quote cospeciation event where you and a common

433
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Speaker 1: ancestor split.

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Speaker 3: This is a host switch.

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Speaker 1: Oh do you want to guess where we got our

436
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Speaker 1: pubic lice from?

437
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Speaker 2: Hold on, So you're telling me that the pubic lice

438
00:21:10,200 --> 00:21:12,320
Speaker 2: are not a branch of the head lice which then

439
00:21:12,400 --> 00:21:16,360
Speaker 2: drifted off because they were separated by the ocean of

440
00:21:16,400 --> 00:21:19,000
Speaker 2: my belly. Yep, but that instead they jumped from some

441
00:21:19,119 --> 00:21:24,480
Speaker 2: other critter. Uh huh, oh boy, I'm going to guess raccoons.

442
00:21:25,960 --> 00:21:29,480
Speaker 2: You should have seen Kelly's face. What's wrong with guessing raccoons.

443
00:21:29,720 --> 00:21:33,320
Speaker 2: Raccoons have been part of human history for a long time, and.

444
00:21:38,119 --> 00:21:41,040
Speaker 1: I don't think I think raccoons are not like an

445
00:21:41,080 --> 00:21:42,600
Speaker 1: African or Asian species.

446
00:21:43,119 --> 00:21:45,239
Speaker 2: Okay, okay, I'm gonna guess. Give me another guests, give

447
00:21:45,240 --> 00:21:49,960
Speaker 2: me another guess. African or Asian species rats.

448
00:21:50,119 --> 00:21:51,919
Speaker 3: That's a good guess. But it's gorillas.

449
00:21:52,080 --> 00:21:52,919
Speaker 2: It's gorillas.

450
00:21:53,200 --> 00:21:56,680
Speaker 1: Okay, it's not a super distant ancestor, but it suggests

451
00:21:56,680 --> 00:21:58,800
Speaker 1: that that you know, we must have been having physical

452
00:21:58,840 --> 00:22:01,399
Speaker 1: contact with gorillas, and this is not going to be

453
00:22:01,720 --> 00:22:04,840
Speaker 1: that kind of show. The physical contact doesn't need to

454
00:22:04,840 --> 00:22:07,679
Speaker 1: have been like dirty contact. You can imagine that you

455
00:22:08,119 --> 00:22:10,359
Speaker 1: slaughtered a gorilla to eat it, and it was like

456
00:22:10,520 --> 00:22:13,520
Speaker 1: in your lap while you were butchering it or whatever.

457
00:22:13,600 --> 00:22:16,160
Speaker 1: But somehow we got close enough to them that their

458
00:22:16,280 --> 00:22:20,480
Speaker 1: lice jumped and took up habitation in our pubic region.

459
00:22:20,560 --> 00:22:24,160
Speaker 2: All right, First, orient me on gorillas and chimps and humans.

460
00:22:24,760 --> 00:22:27,840
Speaker 2: Humans and chimps split most recently six million years ago.

461
00:22:28,240 --> 00:22:31,800
Speaker 2: Gorillas are one split back or chimps include gorillas or

462
00:22:31,800 --> 00:22:32,520
Speaker 2: how does that work?

463
00:22:32,680 --> 00:22:34,560
Speaker 3: They're at least one split back.

464
00:22:34,920 --> 00:22:38,440
Speaker 1: We're all great apes, but they're like a few splits back.

465
00:22:38,760 --> 00:22:42,280
Speaker 2: Okay, So but the gorilla split is before the chimp split. Yes,

466
00:22:42,359 --> 00:22:45,679
Speaker 2: so you have gorilla lice and then chimp human lice,

467
00:22:45,800 --> 00:22:47,720
Speaker 2: and then chimp human lice split into chimp lice and

468
00:22:47,800 --> 00:22:50,960
Speaker 2: human lice. And now you're saying that the gorilla lice

469
00:22:51,320 --> 00:22:53,400
Speaker 2: contrary to what we were saying earlier about how lice

470
00:22:53,480 --> 00:22:56,280
Speaker 2: don't jump from species to species, this is one example

471
00:22:56,280 --> 00:22:59,199
Speaker 2: of when it did, and it somehow went from some

472
00:22:59,320 --> 00:23:01,439
Speaker 2: gorilla to somebody's pubic island.

473
00:23:01,840 --> 00:23:03,879
Speaker 1: Yes, right, so, so I mean sometimes you do you

474
00:23:03,920 --> 00:23:07,359
Speaker 1: get jumps and then that species specializes and so like,

475
00:23:07,800 --> 00:23:11,600
Speaker 1: you don't find human lice typically living on gorilla now

476
00:23:11,640 --> 00:23:14,400
Speaker 1: because they've become like, you know, pretty distinct separate species.

477
00:23:14,720 --> 00:23:17,760
Speaker 2: And so do we know when this jump happened? Like

478
00:23:17,800 --> 00:23:21,160
Speaker 2: it must have happened after humans and chimps split six

479
00:23:21,240 --> 00:23:22,200
Speaker 2: or seven million years.

480
00:23:22,080 --> 00:23:24,879
Speaker 1: Ago, right, Yes, so we think it happened about three

481
00:23:25,040 --> 00:23:29,280
Speaker 1: or four million years ago. As you mentioned, the split

482
00:23:29,359 --> 00:23:33,000
Speaker 1: with gorillas was even farther back than six million years

483
00:23:33,160 --> 00:23:37,359
Speaker 1: And so the fact that these lice jumped onto humans

484
00:23:37,359 --> 00:23:39,600
Speaker 1: three to four million years ago suggests that this is

485
00:23:39,640 --> 00:23:43,520
Speaker 1: not something where the lice were like following their ancestors

486
00:23:43,560 --> 00:23:45,840
Speaker 1: what they were doing over evolutionary time. This was just

487
00:23:45,920 --> 00:23:48,919
Speaker 1: like a jump that happened because gorillas and humans came

488
00:23:48,960 --> 00:23:52,120
Speaker 1: in physical contact. Their lice for some reason were able

489
00:23:52,119 --> 00:23:54,359
Speaker 1: to make the jump, and they were like, sweet, now

490
00:23:54,440 --> 00:23:55,320
Speaker 1: we're human lice.

491
00:23:55,600 --> 00:23:57,639
Speaker 2: Right. So I had two questions about that. One, Okay,

492
00:23:57,680 --> 00:24:00,840
Speaker 2: does that say something about the similarity between gorilla hair

493
00:24:01,000 --> 00:24:02,200
Speaker 2: and human pubic hair?

494
00:24:02,320 --> 00:24:03,760
Speaker 3: Hmm? I could.

495
00:24:03,960 --> 00:24:05,800
Speaker 2: And number two, how do we know this happened three

496
00:24:05,880 --> 00:24:06,879
Speaker 2: or four million years ago?

497
00:24:07,560 --> 00:24:09,479
Speaker 3: Okay? So one, I don't know.

498
00:24:09,520 --> 00:24:13,400
Speaker 1: Maybe maybe maybe gorilla hair is kind of like human pubic.

499
00:24:13,080 --> 00:24:15,960
Speaker 2: Hair, I'm gonna look at gorillas pretty differently from now on.

500
00:24:17,040 --> 00:24:19,359
Speaker 3: Well, maybe you should.

501
00:24:19,960 --> 00:24:21,760
Speaker 1: And the way that we time these things is you

502
00:24:21,800 --> 00:24:24,920
Speaker 1: can find certain genes in the human body that are

503
00:24:25,000 --> 00:24:29,520
Speaker 1: really important, so they shouldn't change much because if they change,

504
00:24:29,520 --> 00:24:32,520
Speaker 1: it could mess up something absolutely fundamental. Yeah, And then

505
00:24:32,800 --> 00:24:37,040
Speaker 1: you look at those genes in closely related species, and

506
00:24:37,440 --> 00:24:41,400
Speaker 1: based on the number of spots in the sequence where

507
00:24:41,440 --> 00:24:45,960
Speaker 1: there's differences, you can time how long they separated. So

508
00:24:46,000 --> 00:24:48,520
Speaker 1: if there's only one spot where they're different, they probably

509
00:24:48,640 --> 00:24:51,760
Speaker 1: didn't separate that long ago. But if there's like fifty

510
00:24:51,800 --> 00:24:54,560
Speaker 1: spots that are different than they probably separated a long

511
00:24:54,600 --> 00:24:58,520
Speaker 1: time ago. But it's not just long time ago. We

512
00:24:58,600 --> 00:25:01,840
Speaker 1: have what are called like molecular clocks, where essentially you

513
00:25:01,880 --> 00:25:04,240
Speaker 1: can look at the rate at which different genes tend

514
00:25:04,240 --> 00:25:07,280
Speaker 1: to pick up mutations and then back calculate how long

515
00:25:07,320 --> 00:25:07,960
Speaker 1: it must have been.

516
00:25:08,080 --> 00:25:10,240
Speaker 2: All right, So we look at gorilla lice and we

517
00:25:10,320 --> 00:25:13,200
Speaker 2: compare it to human pubic lice, and we see these

518
00:25:13,240 --> 00:25:17,040
Speaker 2: are pretty similar, and that's why we think this jump happened.

519
00:25:17,320 --> 00:25:19,960
Speaker 2: We also see there are differences, and by the number

520
00:25:20,000 --> 00:25:22,840
Speaker 2: of differences we can guess when this happened because we

521
00:25:22,880 --> 00:25:25,359
Speaker 2: know how long it takes to make these differences on

522
00:25:25,480 --> 00:25:26,600
Speaker 2: average beautiful.

523
00:25:26,720 --> 00:25:27,640
Speaker 3: Yeah, okay, that's right.

524
00:25:27,680 --> 00:25:31,600
Speaker 2: Wow, that's really fascinating. So we have head lice from

525
00:25:31,600 --> 00:25:34,920
Speaker 2: our common ancestor from chimps, and then pubic lice jumped

526
00:25:34,920 --> 00:25:37,359
Speaker 2: over three or four million years ago. And do we

527
00:25:37,400 --> 00:25:39,879
Speaker 2: think that before that the head lice were just not

528
00:25:40,080 --> 00:25:42,560
Speaker 2: in the pubic region because they were not adapted to it,

529
00:25:43,080 --> 00:25:44,760
Speaker 2: or were they all over the body and then they

530
00:25:44,760 --> 00:25:47,439
Speaker 2: got out competed in the pubic region. For those of

531
00:25:47,520 --> 00:25:50,720
Speaker 2: us who, like our common ancestors, are basically covered in hair,

532
00:25:52,000 --> 00:25:54,040
Speaker 2: do we have lice everywhere or is it only on

533
00:25:54,080 --> 00:25:56,600
Speaker 2: the head and in the pubic region? Like, does anybody

534
00:25:56,600 --> 00:26:00,120
Speaker 2: have back hair lice? As sexy as that sounds.

535
00:26:00,080 --> 00:26:04,080
Speaker 1: Oh yuh so okay, So body lice are lice that

536
00:26:04,119 --> 00:26:06,720
Speaker 1: tend to live in like your clothes, and so the

537
00:26:06,800 --> 00:26:09,439
Speaker 1: point is that there are lice that can be like

538
00:26:09,600 --> 00:26:12,400
Speaker 1: up against your back. But I think lice do well

539
00:26:12,440 --> 00:26:16,359
Speaker 1: in areas where the hair is very thick. Yeah, and well,

540
00:26:16,560 --> 00:26:21,720
Speaker 1: there are some of us who have a dense land bridge.

541
00:26:21,600 --> 00:26:24,480
Speaker 3: Between the head and the lower parts of our bodies.

542
00:26:24,840 --> 00:26:27,080
Speaker 2: I had a roommate from New Jersey once, who looked

543
00:26:27,119 --> 00:26:28,920
Speaker 2: like he was wearing a sweater when he didn't have

544
00:26:28,960 --> 00:26:29,480
Speaker 2: a shirt on.

545
00:26:30,760 --> 00:26:32,280
Speaker 3: I don't know if you had to specify the news

546
00:26:32,320 --> 00:26:33,000
Speaker 3: from New Jersey.

547
00:26:34,160 --> 00:26:37,560
Speaker 2: He liked saying New Jersey, only the strong survive, and

548
00:26:37,640 --> 00:26:40,199
Speaker 2: I just imagined it was a veritable jungle out there.

549
00:26:40,560 --> 00:26:44,040
Speaker 1: Okay, all right, Well, I think for the answers that

550
00:26:44,080 --> 00:26:45,560
Speaker 1: for most people, the hair and the rest of our

551
00:26:45,600 --> 00:26:48,119
Speaker 1: body is not as thick as the hair on our

552
00:26:48,160 --> 00:26:50,959
Speaker 1: heads are in our pubic region, and so you do

553
00:26:51,119 --> 00:26:54,240
Speaker 1: tend to have separation. But I don't know if head

554
00:26:54,280 --> 00:26:55,960
Speaker 1: lice were in the pubic region and then they were

555
00:26:55,960 --> 00:26:59,240
Speaker 1: out competed by lice that could hang on better.

556
00:26:59,480 --> 00:27:03,080
Speaker 3: Yeah, that's a great question. That's a great question. I

557
00:27:03,080 --> 00:27:05,280
Speaker 3: don't know who's spending their life on that one. But

558
00:27:05,560 --> 00:27:06,680
Speaker 3: I didn't find their papers.

559
00:27:06,760 --> 00:27:09,120
Speaker 2: Well here's another question, maybe you don't know the answer to, Okay,

560
00:27:09,359 --> 00:27:12,119
Speaker 2: is on the gorilla, is it the same lice all

561
00:27:12,160 --> 00:27:15,160
Speaker 2: over the body, or like human head lice jump over

562
00:27:15,200 --> 00:27:17,119
Speaker 2: to the gorilla pubic region or something crazy.

563
00:27:17,440 --> 00:27:20,080
Speaker 1: No, I think gorilla just have a species of lice

564
00:27:20,119 --> 00:27:22,639
Speaker 1: that you find all over their body. Okay, okay, And

565
00:27:22,640 --> 00:27:25,960
Speaker 1: so then there's this other thing that maybe you've heard.

566
00:27:26,119 --> 00:27:28,040
Speaker 1: I know I've heard it a couple of times, but

567
00:27:28,080 --> 00:27:30,480
Speaker 1: maybe it's not as common a misconception as I thought.

568
00:27:30,680 --> 00:27:32,919
Speaker 1: But I feel like every once in a while the

569
00:27:33,040 --> 00:27:37,520
Speaker 1: POPSI press will say pubic lice at risk of extinction

570
00:27:37,720 --> 00:27:40,119
Speaker 1: because of rise in bikini waxings.

571
00:27:40,680 --> 00:27:41,440
Speaker 3: Have you heard this?

572
00:27:43,240 --> 00:27:47,240
Speaker 2: I love it. Are Brazilians gonna put pubic lice out

573
00:27:47,280 --> 00:27:48,800
Speaker 2: of business? That's hilarious.

574
00:27:49,000 --> 00:27:51,480
Speaker 1: That's hilarious, And I think the answer is quite clearly no,

575
00:27:51,520 --> 00:27:55,000
Speaker 1: because it would have to be a global out. We

576
00:27:55,040 --> 00:27:58,520
Speaker 1: wouldn't exactly, we would all have to have Brazilians all

577
00:27:58,560 --> 00:28:01,239
Speaker 1: at once and make sure that all of our like

578
00:28:01,320 --> 00:28:03,520
Speaker 1: bed linens had been dried at like one hundred and

579
00:28:03,520 --> 00:28:06,080
Speaker 1: thirty degrees fahrenheit to kill all any pubic lice that

580
00:28:06,080 --> 00:28:07,640
Speaker 1: happened to be off. Although they don't live very long

581
00:28:07,680 --> 00:28:11,200
Speaker 1: off of the human body. But anyway, Yeah, I don't

582
00:28:11,240 --> 00:28:12,600
Speaker 1: think they're at risk of extinction.

583
00:28:12,720 --> 00:28:14,160
Speaker 3: I just really don't buy.

584
00:28:13,920 --> 00:28:16,359
Speaker 1: That, and I'm always amazed when it makes it in

585
00:28:16,359 --> 00:28:18,359
Speaker 1: the press. Again, I'm like, come on, man, it's not

586
00:28:18,400 --> 00:28:19,560
Speaker 1: like everyone is doing this.

587
00:28:19,720 --> 00:28:22,480
Speaker 2: Take them off the endangered species list. They can survive

588
00:28:22,520 --> 00:28:23,000
Speaker 2: on their own.

589
00:28:23,560 --> 00:28:26,000
Speaker 1: Yes, right, And I know that's like a big relief

590
00:28:26,000 --> 00:28:26,480
Speaker 1: for some people.

591
00:28:26,520 --> 00:28:27,720
Speaker 3: But okay, all right.

592
00:28:28,000 --> 00:28:33,560
Speaker 1: So now let's jump into body lice and head lice. Okay, okay,

593
00:28:33,640 --> 00:28:37,560
Speaker 1: So head lice and body lice have very different ways

594
00:28:37,560 --> 00:28:41,440
Speaker 1: that they go about their life. So head lice tend

595
00:28:41,480 --> 00:28:44,520
Speaker 1: to take lots of small meals, and they tend to

596
00:28:44,560 --> 00:28:47,320
Speaker 1: be smaller on average, and they just live in the

597
00:28:47,360 --> 00:28:50,200
Speaker 1: hair and they cling to the hairs. Body lice spend

598
00:28:50,360 --> 00:28:53,960
Speaker 1: a lot of their time living in the nooks and

599
00:28:54,000 --> 00:28:57,640
Speaker 1: crannies of your clothes, and they jump onto your body

600
00:28:57,680 --> 00:29:01,160
Speaker 1: to take a small number of bits big blood meals

601
00:29:01,200 --> 00:29:03,440
Speaker 1: a day, and they also tend to be bigger, and

602
00:29:03,480 --> 00:29:05,920
Speaker 1: then they retreat back into your clothes where they lay

603
00:29:06,320 --> 00:29:06,920
Speaker 1: their eggs.

604
00:29:07,080 --> 00:29:10,280
Speaker 2: All right, so body lice are different species from head.

605
00:29:10,160 --> 00:29:11,760
Speaker 3: Lice, we thought so.

606
00:29:12,240 --> 00:29:15,840
Speaker 1: Oh and so for a long time we thought body

607
00:29:15,880 --> 00:29:19,120
Speaker 1: lice and head lice are different, Like they look different,

608
00:29:19,200 --> 00:29:22,280
Speaker 1: they have different behaviors, and so we were like, okay,

609
00:29:22,320 --> 00:29:24,800
Speaker 1: they're different. And now here is another like story you

610
00:29:24,800 --> 00:29:29,040
Speaker 1: may have heard about lice because they're different. Dating that

611
00:29:29,200 --> 00:29:34,040
Speaker 1: divergence must tell you about when humans started to wear.

612
00:29:33,920 --> 00:29:35,440
Speaker 4: Clothes that would be cool.

613
00:29:35,680 --> 00:29:36,240
Speaker 3: That would be.

614
00:29:36,200 --> 00:29:39,200
Speaker 1: Cool, right, And so what we know from archaeological sites

615
00:29:39,320 --> 00:29:41,320
Speaker 1: is that something like seven hundred and.

616
00:29:41,360 --> 00:29:44,360
Speaker 3: Eighty thousand years ago we were scraping hides.

617
00:29:45,040 --> 00:29:48,280
Speaker 2: Seven hundred and eighty thousand years ago, we're talking almost

618
00:29:48,360 --> 00:29:52,440
Speaker 2: a million years ago. Yeah, yeah, people started preparing leather clothing.

619
00:29:52,840 --> 00:29:56,680
Speaker 1: Well, so almost a million years ago ancient humans were

620
00:29:56,720 --> 00:29:59,840
Speaker 1: scraping hides which could have been used as blankets. Maybe

621
00:29:59,840 --> 00:30:02,280
Speaker 1: they we weren't being used as clothes. We just know

622
00:30:02,320 --> 00:30:03,400
Speaker 1: they were scraping hides.

623
00:30:03,640 --> 00:30:06,280
Speaker 2: Maybe they were being used in bullfights or something, right, yeah.

624
00:30:06,120 --> 00:30:07,720
Speaker 1: Right, who the heck knows what they were being used for.

625
00:30:07,760 --> 00:30:09,280
Speaker 1: Maybe they were being they were umbrellas.

626
00:30:10,880 --> 00:30:13,880
Speaker 2: Maybe they had parades, that's real, pos right, and floats.

627
00:30:14,080 --> 00:30:17,040
Speaker 2: And I remember that humans have been using tools for

628
00:30:17,080 --> 00:30:19,240
Speaker 2: more than a million years, and so we're talking about

629
00:30:19,280 --> 00:30:23,400
Speaker 2: like stone tools here being scraped against the skin kind of.

630
00:30:23,320 --> 00:30:26,160
Speaker 1: Thing, probably, yes, all right, yeah, And then we have

631
00:30:26,320 --> 00:30:30,320
Speaker 1: evidence of eyed needles, so needles that you could put

632
00:30:30,320 --> 00:30:33,000
Speaker 1: it thread through from about forty thousand years ago.

633
00:30:33,160 --> 00:30:37,040
Speaker 2: That is mind blowing. Forty thousand year old eyed needles.

634
00:30:37,160 --> 00:30:37,960
Speaker 2: That's amazing.

635
00:30:37,800 --> 00:30:39,040
Speaker 3: Things so cool, right.

636
00:30:38,960 --> 00:30:40,720
Speaker 2: They're made out of bone or antler or something.

637
00:30:41,360 --> 00:30:43,440
Speaker 1: I don't know what they're made out of, but that

638
00:30:43,960 --> 00:30:47,720
Speaker 1: suggests that we were making pretty complicated clothes at that point.

639
00:30:47,760 --> 00:30:50,400
Speaker 1: We weren't just like cutting a hole and sticking our

640
00:30:50,520 --> 00:30:51,240
Speaker 1: arms through and it.

641
00:30:51,200 --> 00:30:52,200
Speaker 3: Was like toga style.

642
00:30:52,360 --> 00:30:54,600
Speaker 1: We were like, you know, doing something a little bit

643
00:30:54,840 --> 00:30:58,320
Speaker 1: fancier at that point. All right, yeah, okay, so that's

644
00:30:58,320 --> 00:31:01,920
Speaker 1: a pretty big gap. But we think that somewhere between

645
00:31:02,040 --> 00:31:04,680
Speaker 1: one point two and three million years ago is when

646
00:31:04,720 --> 00:31:07,840
Speaker 1: we started to lose our hair, and so, okay, so

647
00:31:07,880 --> 00:31:10,800
Speaker 1: then the question is can the split between body lice

648
00:31:10,840 --> 00:31:13,520
Speaker 1: and head lice tell us anything? Right? And so for

649
00:31:13,560 --> 00:31:15,680
Speaker 1: a while, this paper came out that was going all

650
00:31:15,680 --> 00:31:19,120
Speaker 1: over the place that said it looks like the split

651
00:31:19,240 --> 00:31:22,800
Speaker 1: happened about eighty three thousand to one hundred and seventy

652
00:31:22,840 --> 00:31:23,640
Speaker 1: thousand years.

653
00:31:23,480 --> 00:31:25,840
Speaker 2: Ago between body and head lice.

654
00:31:25,760 --> 00:31:27,600
Speaker 3: Between body and head lice, and so that could be

655
00:31:27,600 --> 00:31:28,720
Speaker 3: when we started wearing.

656
00:31:28,440 --> 00:31:32,760
Speaker 2: Clothes, because wearing clothes creates this new environment for body

657
00:31:32,800 --> 00:31:33,840
Speaker 2: lice to live their own.

658
00:31:33,680 --> 00:31:35,560
Speaker 3: Way, right, because now they can live in our clothes.

659
00:31:35,640 --> 00:31:39,440
Speaker 1: But okay, so I have seen this like set a

660
00:31:39,480 --> 00:31:43,120
Speaker 1: bunch of places, and I've probably repeated it, but we

661
00:31:43,320 --> 00:31:46,520
Speaker 1: don't think that these are separate species anymore. Maybe this

662
00:31:46,680 --> 00:31:49,320
Speaker 1: was a confusion looking at the different clades. So you know,

663
00:31:49,400 --> 00:31:51,240
Speaker 1: remember how we were talking about how we got body

664
00:31:51,280 --> 00:31:53,640
Speaker 1: lice from a lot of different places. But now we've

665
00:31:53,640 --> 00:31:57,360
Speaker 1: done experiments where if you let head lice get to

666
00:31:57,600 --> 00:32:02,120
Speaker 1: super high concentrations, some of them start to change their

667
00:32:02,160 --> 00:32:07,720
Speaker 1: body shape and move into clothes, and so it looks like, actually,

668
00:32:07,760 --> 00:32:11,680
Speaker 1: this is like a way that life's bodies respond to overcrowding.

669
00:32:12,040 --> 00:32:14,640
Speaker 1: They move into a different environment, and so it's not

670
00:32:14,800 --> 00:32:19,160
Speaker 1: different species. It's like an ecology. We'd call this phenotypic plasticity,

671
00:32:19,200 --> 00:32:22,640
Speaker 1: which is to say, something early in your environment tells you, hey,

672
00:32:22,680 --> 00:32:25,040
Speaker 1: you need to prepare for this kind of situation, and

673
00:32:25,200 --> 00:32:28,520
Speaker 1: bodies can go on like a different trajectory, like that's cool.

674
00:32:28,520 --> 00:32:31,240
Speaker 1: There are little aquatic organisms where if they can sense

675
00:32:31,240 --> 00:32:33,680
Speaker 1: that they're a fish in the area, they'll develop like

676
00:32:33,760 --> 00:32:36,400
Speaker 1: spikes on their heads and they can't get rid of

677
00:32:36,400 --> 00:32:38,000
Speaker 1: those spikes. They'll have those spikes for the rest of

678
00:32:38,040 --> 00:32:41,280
Speaker 1: their lives, but they're energetically expensive, so they only develop

679
00:32:41,320 --> 00:32:43,440
Speaker 1: them when they get cues early in life that like,

680
00:32:43,520 --> 00:32:45,160
Speaker 1: this is the kind of environment you live in.

681
00:32:45,680 --> 00:32:49,920
Speaker 2: So human head lice in the right situation, when the

682
00:32:50,040 --> 00:32:53,320
Speaker 2: head is already overcrowded, the babies will develop a different

683
00:32:53,360 --> 00:32:56,240
Speaker 2: form that's better suited to living in the clothing on

684
00:32:56,280 --> 00:32:56,719
Speaker 2: the body.

685
00:32:56,960 --> 00:32:58,720
Speaker 3: It does seem like that is what's happening.

686
00:32:59,040 --> 00:33:01,200
Speaker 2: And do chimp life do that also, or do we

687
00:33:01,200 --> 00:33:04,760
Speaker 2: think this is a feature human lice evolved because humans

688
00:33:04,760 --> 00:33:05,480
Speaker 2: were wearing clothing.

689
00:33:05,840 --> 00:33:08,320
Speaker 1: Yes, so I would not expect that chimp lice would

690
00:33:08,320 --> 00:33:11,480
Speaker 1: have something similar because they've got fur all over their bodies.

691
00:33:11,560 --> 00:33:13,880
Speaker 1: It's not like they have somewhere else to switch to.

692
00:33:14,600 --> 00:33:17,760
Speaker 1: And so I think we think that this is something

693
00:33:17,800 --> 00:33:19,520
Speaker 1: that has to do with like living in clothes.

694
00:33:19,720 --> 00:33:23,200
Speaker 2: And so if we could tell when human lice developed

695
00:33:23,280 --> 00:33:27,480
Speaker 2: this capability, then we could date when this environment became

696
00:33:27,600 --> 00:33:30,160
Speaker 2: available to the lice and learned about when the humans

697
00:33:30,160 --> 00:33:33,640
Speaker 2: started wearing clothing. But that doesn't seem possible. Is that possible, right?

698
00:33:34,080 --> 00:33:37,600
Speaker 1: I wouldn't know how to start there, I mean, because

699
00:33:37,600 --> 00:33:41,840
Speaker 1: they're all interbreeding, right, And so I mean, I think

700
00:33:41,880 --> 00:33:44,040
Speaker 1: what's happening is that they are using genes that they

701
00:33:44,120 --> 00:33:47,800
Speaker 1: already have and they are just expressing them differently. You

702
00:33:47,840 --> 00:33:52,680
Speaker 1: could maybe date it if this ability came from some

703
00:33:53,000 --> 00:33:55,600
Speaker 1: like gene that got added to the population, and you

704
00:33:55,600 --> 00:33:57,520
Speaker 1: could try to time when that gene got in there,

705
00:33:57,560 --> 00:34:00,160
Speaker 1: but as far as I know, yeah, you really can't

706
00:34:00,240 --> 00:34:01,960
Speaker 1: time this. And this is just like so now we

707
00:34:02,000 --> 00:34:04,800
Speaker 1: call them two different kinds of eco morphs. And I

708
00:34:05,160 --> 00:34:08,200
Speaker 1: want to be clear, we really don't understand what's happening

709
00:34:08,239 --> 00:34:10,400
Speaker 1: here very well, but we no longer think of them

710
00:34:10,440 --> 00:34:13,640
Speaker 1: as separate species. It looks like head lice can become

711
00:34:13,719 --> 00:34:15,719
Speaker 1: body lice and they're interbreeding.

712
00:34:15,960 --> 00:34:19,799
Speaker 2: Interesting, all right, And so then head lice really are

713
00:34:20,600 --> 00:34:23,240
Speaker 2: whole body lice except for the pubic region.

714
00:34:23,760 --> 00:34:28,120
Speaker 1: Yeah, yeah, except they sow your kids. You take them

715
00:34:28,160 --> 00:34:31,080
Speaker 1: to I was gonna say lice upon a time. I

716
00:34:31,120 --> 00:34:36,160
Speaker 1: cannot remember. Once upon a life time. That's not what

717
00:34:36,200 --> 00:34:40,440
Speaker 1: it's called, is it once in a lifetime? Okay, right,

718
00:34:41,120 --> 00:34:44,280
Speaker 1: So you took your kids immediately to once in a lifetime,

719
00:34:44,560 --> 00:34:49,360
Speaker 1: which means the density of head lice didn't get very high,

720
00:34:49,440 --> 00:34:52,160
Speaker 1: and so they didn't jump to place. And so in

721
00:34:52,200 --> 00:34:56,640
Speaker 1: the United States, you know, children of wealthy families like

722
00:34:56,920 --> 00:35:01,840
Speaker 1: our children, the lice doesn't get that. But if you

723
00:35:02,040 --> 00:35:05,360
Speaker 1: are someone who's unhoused and doesn't have the opportunity to

724
00:35:05,480 --> 00:35:08,239
Speaker 1: change or wash their clothes for long periods of time,

725
00:35:08,360 --> 00:35:11,440
Speaker 1: or shower for long periods of time. It can build

726
00:35:11,520 --> 00:35:14,880
Speaker 1: up and then body lice become a problem. But what

727
00:35:15,000 --> 00:35:19,480
Speaker 1: has really become a problem is body lice during periods

728
00:35:19,480 --> 00:35:22,880
Speaker 1: in our history where we have had concentration camps or

729
00:35:23,080 --> 00:35:26,600
Speaker 1: war and in those situations you get a lot of

730
00:35:26,640 --> 00:35:30,800
Speaker 1: body lice. And one of the things that differentiates body

731
00:35:30,880 --> 00:35:34,120
Speaker 1: lice from head lice is how their immune system responds

732
00:35:34,719 --> 00:35:37,520
Speaker 1: to pathogens. Oh so when we get back, we're going

733
00:35:37,600 --> 00:35:40,799
Speaker 1: to talk about how body lice have killed millions of

734
00:35:40,840 --> 00:35:44,760
Speaker 1: people throughout history, whereas head lice pretty much don't.

735
00:35:45,000 --> 00:35:47,799
Speaker 2: Wow fascinating. All right, let's take a break. When we

736
00:35:47,840 --> 00:36:08,120
Speaker 2: come back, we'll hear all about the lice wars.

737
00:35:50,480 --> 00:36:14,000
Speaker 1: And we're back, and we've talked about how head lice

738
00:36:14,040 --> 00:36:16,880
Speaker 1: and body lice are very closely related. And our best

739
00:36:16,920 --> 00:36:19,719
Speaker 1: guess at the moment is that body lice are just

740
00:36:20,160 --> 00:36:23,719
Speaker 1: head lice that in a high competition environment, have sort

741
00:36:23,719 --> 00:36:26,480
Speaker 1: of changed the way their body is shaped and now

742
00:36:26,480 --> 00:36:27,720
Speaker 1: they're living in your clothes.

743
00:36:28,080 --> 00:36:31,200
Speaker 2: And so here Kelly is nitpicking the science for all

744
00:36:31,239 --> 00:36:31,440
Speaker 2: of you.

745
00:36:32,000 --> 00:36:34,440
Speaker 1: That's right, that's right, And again I want to clarify

746
00:36:34,480 --> 00:36:36,200
Speaker 1: it there's a lot that we don't know. This is

747
00:36:36,320 --> 00:36:39,440
Speaker 1: like the story literally, as I've been reading like every

748
00:36:39,480 --> 00:36:41,919
Speaker 1: five or ten years worth of like literature chunks, they've

749
00:36:41,960 --> 00:36:43,759
Speaker 1: been like, oh, we've kind of changed our mind about this,

750
00:36:43,880 --> 00:36:45,800
Speaker 1: and so this is an evolving story.

751
00:36:46,080 --> 00:36:48,359
Speaker 3: But part of why we think that body.

752
00:36:48,040 --> 00:36:50,680
Speaker 1: Lice can transmit disease is that one of the things

753
00:36:50,719 --> 00:36:53,439
Speaker 1: that differs between head and body lice is how they

754
00:36:53,600 --> 00:36:57,360
Speaker 1: respond when they get infected with a pathogen and the

755
00:36:57,480 --> 00:37:02,200
Speaker 1: volume of their blood meals changes. So a disease that's

756
00:37:02,239 --> 00:37:05,520
Speaker 1: transmitted by body lice that has been absolutely horrible for

757
00:37:05,640 --> 00:37:09,120
Speaker 1: humans in the past is called epidemic typhus.

758
00:37:09,560 --> 00:37:10,200
Speaker 2: Sounds bad.

759
00:37:10,640 --> 00:37:13,480
Speaker 3: I hate the word typhus.

760
00:37:12,960 --> 00:37:17,640
Speaker 1: Because there are three different kinds of typhises. They're all

761
00:37:17,760 --> 00:37:21,880
Speaker 1: very different, and it's different than typhoid fever. So just

762
00:37:22,000 --> 00:37:24,600
Speaker 1: keep in mind that there's a lot of other things

763
00:37:24,600 --> 00:37:26,160
Speaker 1: that you might have heard about that are not the

764
00:37:26,160 --> 00:37:29,080
Speaker 1: thing we're about to talk about right now, But epidemic

765
00:37:29,200 --> 00:37:31,600
Speaker 1: typhus is what we're talking about, and it is caused

766
00:37:31,600 --> 00:37:36,239
Speaker 1: by a bacteria called Ricketsia prawazechii. And Daniel's like, why

767
00:37:36,239 --> 00:37:37,759
Speaker 1: did you have to say the scientific name?

768
00:37:37,960 --> 00:37:38,480
Speaker 3: And Daniel.

769
00:37:38,520 --> 00:37:40,279
Speaker 1: I had to say the scientific name, because that is

770
00:37:40,320 --> 00:37:42,640
Speaker 1: the way you can be sure that you are talking

771
00:37:42,680 --> 00:37:45,600
Speaker 1: about the disease that I'm about to tell you about.

772
00:37:45,840 --> 00:37:47,880
Speaker 2: Look, I've succeeded. I don't even need to make my

773
00:37:47,920 --> 00:37:51,000
Speaker 2: objection anymore. It's already in your brain. And now I

774
00:37:51,080 --> 00:37:53,759
Speaker 2: just have you questioning yourself, which is good because this

775
00:37:53,880 --> 00:37:56,360
Speaker 2: means you only give us the Latin name when we

776
00:37:56,520 --> 00:37:58,960
Speaker 2: actually need it, so I can retire.

777
00:38:00,080 --> 00:38:02,400
Speaker 1: Well, I look forward to when you stop telling us

778
00:38:02,400 --> 00:38:03,880
Speaker 1: about all the different particles and you call it a

779
00:38:03,960 --> 00:38:05,040
Speaker 1: particle one, two, and three.

780
00:38:05,120 --> 00:38:06,359
Speaker 3: But anyway, all right, all.

781
00:38:06,360 --> 00:38:08,080
Speaker 2: Right, So what does this bacterium do?

782
00:38:08,480 --> 00:38:10,719
Speaker 1: So this is a nasty bacteria. So the lice get

783
00:38:10,719 --> 00:38:13,399
Speaker 1: infected by taking a blood meal from a human who

784
00:38:13,480 --> 00:38:17,160
Speaker 1: already has the bacteria in their body. Okay, the bacteria

785
00:38:17,760 --> 00:38:21,680
Speaker 1: replicates inside of the lice and eventually is going to

786
00:38:21,800 --> 00:38:23,319
Speaker 1: kill the lice also.

787
00:38:23,800 --> 00:38:24,600
Speaker 3: And so when we.

788
00:38:24,520 --> 00:38:27,399
Speaker 1: Talk about malaria, we talk about how the mosquito gives

789
00:38:27,440 --> 00:38:30,080
Speaker 1: it to people when they bite you, and it essentially

790
00:38:30,160 --> 00:38:33,000
Speaker 1: like comes out in the saliva into our body. That's

791
00:38:33,000 --> 00:38:35,359
Speaker 1: not what happens here. What happens here is that the

792
00:38:35,440 --> 00:38:39,760
Speaker 1: lice poop on your body or die on your body. Oh,

793
00:38:39,760 --> 00:38:42,760
Speaker 1: and all of those bites are itchy. So you scratch,

794
00:38:42,800 --> 00:38:46,279
Speaker 1: and when you scratch, you scratch the bacteria which is

795
00:38:46,320 --> 00:38:48,440
Speaker 1: still present in the poop and the body parts of

796
00:38:48,480 --> 00:38:51,839
Speaker 1: the lice. You scratch that into your body, or maybe

797
00:38:51,880 --> 00:38:53,319
Speaker 1: you get it on your hands, and then you rub

798
00:38:53,320 --> 00:38:55,520
Speaker 1: your eyes and it gets in through the mucous membranes.

799
00:38:55,800 --> 00:38:58,120
Speaker 2: This is if I don't have the bacterium in my

800
00:38:58,200 --> 00:39:01,120
Speaker 2: blood yet, but I've gotten a house from somebody who

801
00:39:01,280 --> 00:39:04,040
Speaker 2: does have it, that it can cross back into my

802
00:39:04,160 --> 00:39:06,160
Speaker 2: body through an I've scratched.

803
00:39:06,640 --> 00:39:07,640
Speaker 3: Yeah, exactly right.

804
00:39:07,680 --> 00:39:10,319
Speaker 1: So if you borrow the coat of somebody who has

805
00:39:10,520 --> 00:39:14,120
Speaker 1: lice and they gave their lice epidemic typhus, and then

806
00:39:14,160 --> 00:39:16,200
Speaker 1: that lice dies on you or poops on you and

807
00:39:16,239 --> 00:39:17,680
Speaker 1: you scratch, now you've got it.

808
00:39:17,640 --> 00:39:18,160
Speaker 2: Oh boy.

809
00:39:18,480 --> 00:39:21,360
Speaker 1: And so what it does is it lives in the

810
00:39:21,400 --> 00:39:24,480
Speaker 1: cells that line your blood vessels, and in particular, it

811
00:39:24,520 --> 00:39:27,399
Speaker 1: tends to line the blood vessels when they get really thin,

812
00:39:27,840 --> 00:39:31,120
Speaker 1: and this includes the blood vessels in your brain. So

813
00:39:31,160 --> 00:39:34,480
Speaker 1: the root for typhus is a Greek word. I think

814
00:39:34,520 --> 00:39:38,000
Speaker 1: that means hazy or foggy, and that refers to the

815
00:39:38,040 --> 00:39:41,160
Speaker 1: fact that it has a lot of neurological symptoms that

816
00:39:41,239 --> 00:39:44,759
Speaker 1: make I know, I know it's the worst. And so

817
00:39:44,800 --> 00:39:46,759
Speaker 1: what it's doing is it like it's living in your

818
00:39:46,760 --> 00:39:49,480
Speaker 1: blood vessels, including the ones in your brain, and it

819
00:39:49,560 --> 00:39:52,480
Speaker 1: replicates and replicates and replicates until it bursts open those

820
00:39:52,520 --> 00:39:56,240
Speaker 1: blood vessels. And now you've got these leaky blood vessels.

821
00:39:56,600 --> 00:39:58,400
Speaker 4: That sounds bad, super bad.

822
00:39:58,480 --> 00:40:01,920
Speaker 1: And then your body responds trying to clot and stop

823
00:40:02,000 --> 00:40:04,560
Speaker 1: that leaking. And so now you've also got blood clots

824
00:40:05,080 --> 00:40:07,760
Speaker 1: in your brain or in these other parts of your body.

825
00:40:08,200 --> 00:40:10,480
Speaker 1: And so there tend to be a lot of neurological symptoms.

826
00:40:10,520 --> 00:40:14,240
Speaker 1: In the past, this parasite was associated with death rates

827
00:40:14,320 --> 00:40:18,280
Speaker 1: up to sixty percent. If you survived, that was great,

828
00:40:18,320 --> 00:40:20,759
Speaker 1: but a lot of people you know, would not survive it.

829
00:40:20,960 --> 00:40:24,080
Speaker 2: Wow, And so have there been big outbreaks of this?

830
00:40:24,120 --> 00:40:25,400
Speaker 2: Is this why it's called epidemic?

831
00:40:25,960 --> 00:40:28,160
Speaker 4: Yes? Yes, you shouldn't say yes.

832
00:40:28,080 --> 00:40:32,800
Speaker 2: So enthusiastically, Kelly, we're talking with a lot of suffering here.

833
00:40:33,239 --> 00:40:34,040
Speaker 2: Why am I laughing?

834
00:40:34,120 --> 00:40:37,200
Speaker 1: I'm not right, yeah right, I'm not excited about the suffering.

835
00:40:37,320 --> 00:40:40,440
Speaker 1: I'm interested in the fact that pretty much none of

836
00:40:40,520 --> 00:40:45,200
Speaker 1: us have heard of epidemic typhus, because this is like

837
00:40:45,280 --> 00:40:47,279
Speaker 1: a problem that doesn't bother most of us in our.

838
00:40:47,239 --> 00:40:48,320
Speaker 3: Day to day lives anymore.

839
00:40:48,560 --> 00:40:49,479
Speaker 2: Yay, yay.

840
00:40:49,760 --> 00:40:54,160
Speaker 1: But for example, during World War One, the Bolshevik Revolution happened,

841
00:40:54,280 --> 00:40:58,719
Speaker 1: and so Lenin and the rest of his Bolsheviks were

842
00:40:58,920 --> 00:41:02,000
Speaker 1: essentially starting a civil or within Russia. They didn't want

843
00:41:02,040 --> 00:41:03,880
Speaker 1: to be part of World War One anymore, so they

844
00:41:03,960 --> 00:41:06,960
Speaker 1: tried to pull out. The Germans sort of kept coming anyway,

845
00:41:07,360 --> 00:41:10,160
Speaker 1: and so you had this civil war happening in Russia

846
00:41:10,200 --> 00:41:12,960
Speaker 1: at the same time as World War One, and things

847
00:41:13,000 --> 00:41:16,839
Speaker 1: were just an absolute disaster. Epidemic typhus started sweeping through.

848
00:41:16,920 --> 00:41:20,200
Speaker 1: People couldn't like wash their clothes or shower regularly enough,

849
00:41:20,239 --> 00:41:24,040
Speaker 1: and something like twenty to thirty million people got infected

850
00:41:24,080 --> 00:41:27,640
Speaker 1: by epidemic typhus, and like two to three million people died,

851
00:41:27,920 --> 00:41:31,279
Speaker 1: oh man, right during World War One, So that was

852
00:41:31,440 --> 00:41:34,440
Speaker 1: obviously not good. Another thing that's kind of a bummer

853
00:41:34,520 --> 00:41:37,160
Speaker 1: from the perspective of humans having this disease is that

854
00:41:37,360 --> 00:41:39,920
Speaker 1: it seems to be able to like live sort of

855
00:41:40,040 --> 00:41:43,440
Speaker 1: quietly in our body for a long time, so you

856
00:41:43,480 --> 00:41:47,840
Speaker 1: can be fine, and then something stressful happens, and now

857
00:41:48,040 --> 00:41:51,640
Speaker 1: you have a less intense version of epidemic typhus, but

858
00:41:51,719 --> 00:41:54,680
Speaker 1: you have epidemic typhus again. It used to be called

859
00:41:54,800 --> 00:41:57,799
Speaker 1: I think breathement syndrome because this would like people who

860
00:41:57,800 --> 00:42:00,799
Speaker 1: would be absolutely stressed out in devas dated because someone

861
00:42:00,800 --> 00:42:04,600
Speaker 1: they love died would end up having epidemic typhus essentially

862
00:42:04,680 --> 00:42:07,239
Speaker 1: wake back up again and make them feel miserable all

863
00:42:07,280 --> 00:42:07,880
Speaker 1: over again.

864
00:42:08,000 --> 00:42:10,600
Speaker 2: What's the connection between stress and the disease waking up?

865
00:42:10,960 --> 00:42:11,280
Speaker 3: Ah?

866
00:42:11,280 --> 00:42:14,520
Speaker 1: So like uh diseases, even like shingles. So shingles is

867
00:42:14,560 --> 00:42:17,120
Speaker 1: when the chicken pox virus wakes back up again, which

868
00:42:17,160 --> 00:42:19,680
Speaker 1: is really bad, right, Yeah, Oh my gosh. Zach had

869
00:42:19,680 --> 00:42:21,640
Speaker 1: it and he felt like he was having a heart attack.

870
00:42:21,680 --> 00:42:24,640
Speaker 1: It was absolutely horrible. And so there are viruses and

871
00:42:24,680 --> 00:42:27,680
Speaker 1: bacteria that can infect you when you're young, and then

872
00:42:27,760 --> 00:42:30,160
Speaker 1: years later when you get super stressed out that can

873
00:42:30,160 --> 00:42:33,239
Speaker 1: suppress your immune system. And when your immune system is suppressed,

874
00:42:33,800 --> 00:42:37,520
Speaker 1: these organisms i'd wake back up again is a very

875
00:42:37,520 --> 00:42:39,799
Speaker 1: anthropomorphic way of saying it. But they take advantage of

876
00:42:39,840 --> 00:42:42,799
Speaker 1: your immune systems weak in state to essentially give you

877
00:42:42,840 --> 00:42:45,320
Speaker 1: the disease all over again, or a slightly different version

878
00:42:45,400 --> 00:42:48,479
Speaker 1: of the disgus. So shingles is like the adult version

879
00:42:48,520 --> 00:42:49,560
Speaker 1: of chicken pox.

880
00:42:49,320 --> 00:42:51,879
Speaker 2: And that's for people who had chicken pox as a kid. Right,

881
00:42:51,880 --> 00:42:54,279
Speaker 2: So chicken pox parties bad idea.

882
00:42:54,120 --> 00:42:55,720
Speaker 3: Well, yeah, right, bad idea.

883
00:42:56,080 --> 00:43:00,160
Speaker 1: Vaccinations for chicken pox, great idea. I don't expect that

884
00:43:00,200 --> 00:43:02,520
Speaker 1: my children are ever going to have to suffer through

885
00:43:02,520 --> 00:43:05,680
Speaker 1: shingles like my husband did, or like I might have to.

886
00:43:05,719 --> 00:43:07,360
Speaker 3: Who knows what awaits in the future.

887
00:43:07,719 --> 00:43:12,120
Speaker 2: Yay chicken pox roulette. So in this case, we're talking

888
00:43:12,120 --> 00:43:15,040
Speaker 2: about a disease that's in your blood can lay dormant,

889
00:43:15,320 --> 00:43:17,160
Speaker 2: but then when you get stressed out or you have

890
00:43:17,239 --> 00:43:19,960
Speaker 2: a terrible life event, it can rear its ugly head.

891
00:43:20,000 --> 00:43:22,240
Speaker 2: That's terrible, take advantage of you when you're down.

892
00:43:22,719 --> 00:43:24,480
Speaker 3: Totally terrible, totally terrible.

893
00:43:24,520 --> 00:43:26,560
Speaker 1: But you know, for most of us in the United States,

894
00:43:26,640 --> 00:43:30,520
Speaker 1: we haven't been exposed to epidemic typhus. We haven't been

895
00:43:30,560 --> 00:43:34,160
Speaker 1: in like war or refugee situations, because we're very lucky

896
00:43:34,160 --> 00:43:34,840
Speaker 1: in that regard.

897
00:43:35,120 --> 00:43:37,759
Speaker 2: But why is that exactly? Is that because we just

898
00:43:37,800 --> 00:43:40,400
Speaker 2: don't have very many lice, or because the lice we

899
00:43:40,440 --> 00:43:43,640
Speaker 2: do have are not infected or both both.

900
00:43:43,680 --> 00:43:47,560
Speaker 1: So the big thing is that your head lice don't

901
00:43:47,600 --> 00:43:51,640
Speaker 1: become body lice unless you are not showering or washing

902
00:43:51,640 --> 00:43:54,880
Speaker 1: your clothes regularly, right, And that happens more often in

903
00:43:54,920 --> 00:43:58,400
Speaker 1: situations where you're a refugee, or you're.

904
00:43:58,440 --> 00:44:00,879
Speaker 3: Unhomed, or it's a war.

905
00:44:01,120 --> 00:44:01,560
Speaker 2: Got it.

906
00:44:01,719 --> 00:44:06,200
Speaker 1: So, for example, lice diseases, this one and others, including

907
00:44:06,200 --> 00:44:09,600
Speaker 1: one called trench fever, was a really big problem in

908
00:44:09,680 --> 00:44:12,600
Speaker 1: World War One when they were in the trenches and

909
00:44:12,760 --> 00:44:15,960
Speaker 1: they couldn't get out to shower regularly, and so the

910
00:44:16,080 --> 00:44:18,319
Speaker 1: lice built up to very high numbers. The head lice

911
00:44:18,360 --> 00:44:22,160
Speaker 1: became body lice, and now they're transmitting disease and you're

912
00:44:22,200 --> 00:44:25,120
Speaker 1: in close quarters, so it's jumping from one person to another.

913
00:44:25,360 --> 00:44:26,480
Speaker 2: Got it, I see.

914
00:44:26,719 --> 00:44:30,840
Speaker 1: But in the United States there's a reservoir for the

915
00:44:30,880 --> 00:44:33,399
Speaker 1: bacteria which I won't say again so that Daniel doesn't

916
00:44:33,400 --> 00:44:38,440
Speaker 1: get upset with me. And the reservoir are little flying squirrels.

917
00:44:38,680 --> 00:44:42,360
Speaker 1: What Yeah, So people who interact with flying squirrels or

918
00:44:42,400 --> 00:44:45,000
Speaker 1: their nests where the lice can get left behind for

919
00:44:45,000 --> 00:44:48,160
Speaker 1: a little while, are some of the rare cases of

920
00:44:48,239 --> 00:44:50,560
Speaker 1: epidemic typhus that you see in the United States.

921
00:44:50,600 --> 00:44:52,600
Speaker 2: And when you say reservoir, you don't mean like a

922
00:44:52,680 --> 00:44:55,120
Speaker 2: lake out there with water we can drink. You mean,

923
00:44:55,239 --> 00:44:58,800
Speaker 2: someplace where the disease is like hiding out and hanging

924
00:44:58,800 --> 00:44:59,719
Speaker 2: out and waiting to.

925
00:44:59,719 --> 00:45:03,360
Speaker 1: Stry quite so, yes, that's right, that's right. So for

926
00:45:03,400 --> 00:45:05,680
Speaker 1: the most part, we don't worry about epidemic typhus. If

927
00:45:05,680 --> 00:45:08,359
Speaker 1: somebody does happen to get epidemic typhus, you can treat

928
00:45:08,360 --> 00:45:10,399
Speaker 1: it with doxycycline, which is an antibiotic.

929
00:45:10,640 --> 00:45:11,759
Speaker 2: Thank you, Big Pharma.

930
00:45:11,840 --> 00:45:12,640
Speaker 3: That's right. Yeah.

931
00:45:12,719 --> 00:45:15,160
Speaker 1: Yeah, So being in the United States is pretty great

932
00:45:15,200 --> 00:45:18,520
Speaker 1: when you are able to regularly shower and wash your clothes.

933
00:45:19,520 --> 00:45:22,680
Speaker 1: Hans Zinzer, who's like famous for writing Rats, Lice and History,

934
00:45:22,719 --> 00:45:25,000
Speaker 1: which is like a book on epidemic typhus.

935
00:45:25,080 --> 00:45:26,480
Speaker 2: I've been itching to read that book.

936
00:45:26,760 --> 00:45:27,520
Speaker 3: Ah.

937
00:45:27,560 --> 00:45:30,640
Speaker 1: I honestly, I don't recommend it. I like he goes

938
00:45:30,680 --> 00:45:33,879
Speaker 1: on long tirades about like art and science and they're

939
00:45:33,920 --> 00:45:37,520
Speaker 1: not particularly insightful, and like, oh wow, you gotta get

940
00:45:37,680 --> 00:45:39,440
Speaker 1: at least like twenty five percent of the way through

941
00:45:39,440 --> 00:45:41,360
Speaker 1: the book before he starts talking about typhus, and you're like,

942
00:45:41,400 --> 00:45:43,319
Speaker 1: get to the point, and he starts each chapter with

943
00:45:43,640 --> 00:45:46,040
Speaker 1: I'm sorry about the digression, and you're like, you should

944
00:45:46,160 --> 00:45:47,920
Speaker 1: be get to Typhus.

945
00:45:48,480 --> 00:45:50,719
Speaker 2: Sounds like the book needed an editor, I know.

946
00:45:50,760 --> 00:45:53,160
Speaker 1: Right, And so anyway, he has this great quote, Typhus

947
00:45:53,200 --> 00:45:56,279
Speaker 1: will continue to break into the open whenever human stupidity

948
00:45:56,320 --> 00:45:59,560
Speaker 1: and brutality give it a chance. So anyway it happens

949
00:45:59,600 --> 00:46:03,640
Speaker 1: to come a long with war and refugee situations.

950
00:46:03,719 --> 00:46:04,880
Speaker 2: That is a pretty great quote.

951
00:46:04,960 --> 00:46:06,879
Speaker 3: That is a pretty great quote. He does. He's got

952
00:46:06,880 --> 00:46:08,160
Speaker 3: a lot of great quotes in the book.

953
00:46:08,360 --> 00:46:10,480
Speaker 1: Got He's got another quote about how you should feel

954
00:46:10,520 --> 00:46:14,560
Speaker 1: bad because the lice give up their little ghost when

955
00:46:14,560 --> 00:46:17,160
Speaker 1: they die from Typhus, and so maybe you should like

956
00:46:17,480 --> 00:46:19,080
Speaker 1: not feel so bad about the lice.

957
00:46:19,160 --> 00:46:21,640
Speaker 3: And if anybody wants a lot more detail on.

958
00:46:21,600 --> 00:46:25,080
Speaker 1: These diseases, they should check out the Typhus episode on

959
00:46:25,120 --> 00:46:28,200
Speaker 1: this podcast will Kill You Anyway. Lots of additional great

960
00:46:28,239 --> 00:46:29,320
Speaker 1: quotes in that podcast.

961
00:46:29,440 --> 00:46:32,080
Speaker 2: I didn't mean to brush off the suffering of the lice.

962
00:46:32,320 --> 00:46:35,000
Speaker 3: Uh, yeah, that's right. I don't feel as bad for

963
00:46:35,080 --> 00:46:36,040
Speaker 3: lice as I do for people.

964
00:46:36,200 --> 00:46:40,759
Speaker 1: Okay, anyway, there's also lous born relapsing fever. This is

965
00:46:40,800 --> 00:46:42,920
Speaker 1: caused by a different kind of bacteria. It gives you

966
00:46:42,960 --> 00:46:45,799
Speaker 1: fevers that kind of come and go. There's estimates that

967
00:46:45,960 --> 00:46:49,280
Speaker 1: around World War One, about five million people died from

968
00:46:49,600 --> 00:46:52,440
Speaker 1: this fever as well. And this was happening like in

969
00:46:52,480 --> 00:46:55,560
Speaker 1: the trenches and stuff. And then there's trench fever, which

970
00:46:55,560 --> 00:46:57,319
Speaker 1: we talked about a little bit earlier, which was a

971
00:46:57,360 --> 00:46:59,879
Speaker 1: problem for the people living in trenches. But it's still

972
00:47:00,160 --> 00:47:03,800
Speaker 1: problem now in some parts of the world where lice

973
00:47:04,200 --> 00:47:07,359
Speaker 1: can kind of reach high numbers. But so we talked

974
00:47:07,400 --> 00:47:09,839
Speaker 1: about how, you know, millions of people died during World

975
00:47:09,880 --> 00:47:14,200
Speaker 1: War One from diseases transmitted by lice. There's another figure

976
00:47:14,239 --> 00:47:16,360
Speaker 1: that goes around a lot when you're you know, reading

977
00:47:16,400 --> 00:47:18,960
Speaker 1: through the Lyces literature, as some of us do, And

978
00:47:20,840 --> 00:47:25,480
Speaker 1: there is a cemetery where some of Napoleon's soldiers from

979
00:47:25,560 --> 00:47:29,680
Speaker 1: the Grand Army were buried, and this was after they

980
00:47:29,680 --> 00:47:32,400
Speaker 1: went to Moscow and were you know, defeated by the

981
00:47:32,480 --> 00:47:37,200
Speaker 1: Russian winter, and about a third of the dental pulpe

982
00:47:37,200 --> 00:47:39,200
Speaker 1: that they went through. So sometimes you can find like

983
00:47:39,239 --> 00:47:43,840
Speaker 1: evidence of bacterial infections in dental pulp in skeletons, about

984
00:47:43,840 --> 00:47:44,640
Speaker 1: a third of them.

985
00:47:44,880 --> 00:47:47,200
Speaker 2: Sorry, dental pulp. This is like the inner part of

986
00:47:47,239 --> 00:47:48,120
Speaker 2: a tooth or something.

987
00:47:48,400 --> 00:47:50,200
Speaker 1: Yeah, yeah, the inner part of the tooth. If you

988
00:47:50,239 --> 00:47:53,520
Speaker 1: can like extract that and do like genetic sequencing on it,

989
00:47:53,960 --> 00:47:54,960
Speaker 1: which they were able to.

990
00:47:55,239 --> 00:47:56,919
Speaker 2: They dug up all these graves.

991
00:47:57,239 --> 00:47:58,480
Speaker 3: Yeah, they dug up all these grapes.

992
00:47:58,840 --> 00:48:01,160
Speaker 1: I mean, this kind of stuff happens a lot for

993
00:48:01,320 --> 00:48:04,359
Speaker 1: historic when you're trying to study history. But anyway, they

994
00:48:04,400 --> 00:48:06,600
Speaker 1: found that a third of the soldiers that were in

995
00:48:06,640 --> 00:48:10,920
Speaker 1: those graves were carrying diseases transmitted by lice, and so

996
00:48:11,160 --> 00:48:13,279
Speaker 1: it looks like lice might have played a role in

997
00:48:13,400 --> 00:48:17,080
Speaker 1: defeating Napoleon's army in addition to the horrible Russian winters.

998
00:48:17,360 --> 00:48:18,440
Speaker 2: Wow, amazing.

999
00:48:18,840 --> 00:48:21,840
Speaker 1: Yeah, But like, just to really emphasize how many people

1000
00:48:21,880 --> 00:48:26,000
Speaker 1: died there, Napoleon went to Moscow with half a million

1001
00:48:26,000 --> 00:48:28,359
Speaker 1: people came back. Do you want to guess how many

1002
00:48:28,400 --> 00:48:29,000
Speaker 1: he came back with.

1003
00:48:29,920 --> 00:48:34,000
Speaker 2: Let's see, twenty percent died from lice. So I'm gonna

1004
00:48:34,000 --> 00:48:35,400
Speaker 2: go on, maybe one hundred.

1005
00:48:35,160 --> 00:48:39,800
Speaker 1: Thousand, three thousand, three thousand, three thousand.

1006
00:48:39,840 --> 00:48:46,280
Speaker 2: Don't sounds so exciting, Kelly. You're talking about human death here, right, okay,

1007
00:48:46,320 --> 00:48:51,400
Speaker 2: three thousand. Now it sounds like you're pretending to care. Well, okay,

1008
00:48:51,440 --> 00:48:54,720
Speaker 2: I care, but like it's dramatic, Yeah, I agree, Yes.

1009
00:48:54,600 --> 00:48:57,000
Speaker 1: My voice is trying to convey like just the like

1010
00:48:57,120 --> 00:48:59,280
Speaker 1: mind blowingness of like, holy cow.

1011
00:48:59,080 --> 00:49:02,160
Speaker 3: That is so many. This is like what was Napoleon

1012
00:49:02,200 --> 00:49:06,279
Speaker 3: doing anyway? History? Okay, so let's wrap things up.

1013
00:49:06,400 --> 00:49:08,600
Speaker 1: There have been a lot of different instances throughout history

1014
00:49:08,640 --> 00:49:13,680
Speaker 1: where lice transmitted diseases have killed millions of humans. Yeh,

1015
00:49:13,920 --> 00:49:16,040
Speaker 1: lucky for us today, especially if you live in a

1016
00:49:16,040 --> 00:49:18,959
Speaker 1: place like the United States. When you get lice, which

1017
00:49:19,000 --> 00:49:23,280
Speaker 1: happens to six to twelve million kids every year. Wow,

1018
00:49:23,360 --> 00:49:25,799
Speaker 1: what you think is, ah, I have to go to

1019
00:49:25,880 --> 00:49:28,719
Speaker 1: once in a life's time again, you don't think, I

1020
00:49:28,760 --> 00:49:30,440
Speaker 1: hope I don't get epidemic typhus.

1021
00:49:30,480 --> 00:49:31,719
Speaker 2: But now I'm gonna think that.

1022
00:49:32,480 --> 00:49:35,319
Speaker 1: Okay, well, your kids are old enough that hopefully they're

1023
00:49:35,360 --> 00:49:36,840
Speaker 1: not bringing home head lice anymore.

1024
00:49:36,920 --> 00:49:38,080
Speaker 2: No, no longer.

1025
00:49:38,200 --> 00:49:40,560
Speaker 1: Yeah, yeah, and so so now we treat this with

1026
00:49:40,760 --> 00:49:44,160
Speaker 1: like you know, with combs and specialized shampoos. There's an

1027
00:49:44,360 --> 00:49:47,200
Speaker 1: interesting new treatment that people are trying out. So lice

1028
00:49:47,640 --> 00:49:51,360
Speaker 1: have an endosymbiotic bacteria, so a bacteria that lives inside

1029
00:49:51,400 --> 00:49:55,440
Speaker 1: of them, and that bacteria is critical for providing the

1030
00:49:55,520 --> 00:49:59,000
Speaker 1: lice with B vitamins, which are not present in human blood.

1031
00:49:59,320 --> 00:50:01,880
Speaker 1: And so people are trying to explore whether or not

1032
00:50:01,920 --> 00:50:05,399
Speaker 1: you can use antibiotics to kill the bacteria that live

1033
00:50:05,560 --> 00:50:08,520
Speaker 1: inside of the lice, and if that will then kill

1034
00:50:08,920 --> 00:50:11,799
Speaker 1: the lice because they need those bacteria, or the lice just.

1035
00:50:11,760 --> 00:50:14,080
Speaker 2: Get like the Lyce's version of scurvy or something.

1036
00:50:14,360 --> 00:50:23,879
Speaker 3: Yeah. H this be a bad head, all right, all right, all.

1037
00:50:23,840 --> 00:50:26,279
Speaker 2: Right, Well this is a fascinating dive into history. It

1038
00:50:26,320 --> 00:50:29,759
Speaker 2: is tragic, of course that lice terrorize people and kill

1039
00:50:29,840 --> 00:50:32,560
Speaker 2: so many people, but it's also fascinating that it can

1040
00:50:32,600 --> 00:50:35,360
Speaker 2: tell us so much about our ancient ancient.

1041
00:50:35,000 --> 00:50:38,600
Speaker 1: History, or that it can confirm what we already think

1042
00:50:38,640 --> 00:50:41,120
Speaker 1: is happening with our ancient ancient history. As I said,

1043
00:50:41,160 --> 00:50:43,160
Speaker 1: I have to be a wet blanket. But still there's

1044
00:50:43,200 --> 00:50:45,440
Speaker 1: lots of interesting stuff going on here. So yes, more

1045
00:50:45,520 --> 00:50:46,479
Speaker 1: money to study lice.

1046
00:50:46,560 --> 00:50:51,080
Speaker 2: But they do tell us about this gorilla human crossover event. Yeah, yeah,

1047
00:50:51,080 --> 00:50:52,200
Speaker 2: that we didn't know about before.

1048
00:50:52,520 --> 00:50:55,640
Speaker 1: I mean, I guess you, like, how interesting is it

1049
00:50:55,880 --> 00:50:58,640
Speaker 1: to know that humans interacted with gorillas in the past,

1050
00:50:58,719 --> 00:51:00,279
Speaker 1: Like I would have guessed that we were killed and

1051
00:51:00,280 --> 00:51:01,000
Speaker 1: eating gorillas.

1052
00:51:01,040 --> 00:51:03,799
Speaker 3: You kill and eat whatever you need to when you're

1053
00:51:04,120 --> 00:51:05,000
Speaker 3: an ancient human.

1054
00:51:05,040 --> 00:51:08,040
Speaker 2: I don't know Kelly's ancestors killed and eight gorillas.

1055
00:51:07,640 --> 00:51:08,160
Speaker 3: All the time.

1056
00:51:08,200 --> 00:51:11,279
Speaker 2: It sounds come on down for a gorilla barbecue at

1057
00:51:11,440 --> 00:51:12,640
Speaker 2: Kelly's ancestors house.

1058
00:51:12,719 --> 00:51:16,000
Speaker 1: That's right, okay, all right, well you're all invited.

1059
00:51:16,160 --> 00:51:18,680
Speaker 2: Did you say you grew up in New Jersey? Not surprised.

1060
00:51:19,000 --> 00:51:25,080
Speaker 1: All my ancestors are largely I guess French and Irish,

1061
00:51:25,200 --> 00:51:27,960
Speaker 1: and so you know, a bunch of us might have died,

1062
00:51:28,280 --> 00:51:31,480
Speaker 1: you know, hiking back from Moscow with Napoleon's grand or

1063
00:51:31,520 --> 00:51:35,120
Speaker 1: may or whatever. And then during the Great Irish Famine,

1064
00:51:35,160 --> 00:51:38,120
Speaker 1: the Potato famine around like eighteen forty five eighteen forty eight,

1065
00:51:38,400 --> 00:51:41,960
Speaker 1: there was also a lot of deaths because of disease

1066
00:51:42,000 --> 00:51:44,480
Speaker 1: at that time, Like if you are starving, you probably

1067
00:51:44,480 --> 00:51:46,640
Speaker 1: don't have the energy to change your clothes or shower.

1068
00:51:46,800 --> 00:51:49,279
Speaker 3: So epidemic Typhus killed a bunch of Irish people there

1069
00:51:49,280 --> 00:51:49,640
Speaker 3: as well.

1070
00:51:49,680 --> 00:51:53,800
Speaker 1: So ancestors on both sides of my family were dying

1071
00:51:53,880 --> 00:51:55,040
Speaker 1: from Typhus.

1072
00:51:55,040 --> 00:51:59,920
Speaker 2: Maybe, she said, gleefully.

1073
00:51:58,040 --> 00:52:00,160
Speaker 1: This is just the tone of voice at which I

1074
00:52:00,239 --> 00:52:01,920
Speaker 1: approach everything in my life.

1075
00:52:02,640 --> 00:52:05,960
Speaker 2: I might consider having different toes or different topics, you know,

1076
00:52:06,120 --> 00:52:08,480
Speaker 2: all right, Or folks out there who want a really

1077
00:52:08,680 --> 00:52:11,319
Speaker 2: bright eulogy write to Kelly, she will come to your

1078
00:52:11,320 --> 00:52:13,479
Speaker 2: funeral and talk gleefully about your death.

1079
00:52:13,920 --> 00:52:16,640
Speaker 1: Yes, if your funeral is a celebration of life, then

1080
00:52:16,680 --> 00:52:21,000
Speaker 1: invite me. If it is a celebration of lice, Oh

1081
00:52:21,040 --> 00:52:23,040
Speaker 1: all right, we need to we need to knock this off.

1082
00:52:23,080 --> 00:52:24,160
Speaker 1: It's time for us to go.

1083
00:52:24,560 --> 00:52:26,640
Speaker 2: Thanks everybody for taking this journey with us.

1084
00:52:27,000 --> 00:52:27,839
Speaker 3: Until next time.

1085
00:52:34,640 --> 00:52:37,040
Speaker 2: Thanks everybody for listening. Please go and do us a

1086
00:52:37,080 --> 00:52:40,359
Speaker 2: favor and rate the show on whatever podcast app you're using.

1087
00:52:40,400 --> 00:52:42,000
Speaker 2: It really helps people find us.

1088
00:52:42,560 --> 00:52:46,480
Speaker 1: Daniel and Kelly's Extraordinary Universe is edited by the amazing

1089
00:52:46,480 --> 00:52:47,200
Speaker 1: Matt Kesselman.

1090
00:52:47,440 --> 00:52:50,680
Speaker 2: He really is a wizard. You can also find us

1091
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Speaker 2: online on Blue Sky, Instagram, and x D and K Universe.

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Speaker 2: Come engage with us.

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Speaker 1: You can email us I had questions at Daniel and Kelly.

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Speaker 1: We really do want to hear.

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Speaker 2: From you, and you can find our website www dot

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Speaker 2: danieland Kelly dot org, where you'll also find an invitation

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Speaker 2: to join our discord where everybody comes and talks about

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Speaker 2: the amazing.

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Speaker 1: Universe, and we also have the most amazing moderators. This

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Speaker 1: is an iHeart podcast. Thanks for joining us.