Speaker 1: Daniel, did you want to ask an alien related question?
Speaker 1: Or are you good?
Speaker 2: Oh my gosh. The answer to that is always yes.
Speaker 3: Green is the answer green?
Speaker 2: Yeah, Katie. My question is what color are alien nipples?
Speaker 4: M you know what, I've always imagined them as lavender.
Speaker 4: Isn't that funny?
Speaker 2: Maybe they also taste like lavender?
Speaker 3: You hey, you know what.
Speaker 4: We're getting into some real strange territory here, right.
Speaker 2: That's a little taste of the conversation we have on
Speaker 2: today's episode. It's not about aliens, mostly though it is
Speaker 2: a little bit, And it's not about nipples mostly again,
Speaker 2: though it is a little bit. It's about babies. How
Speaker 2: many babies should you have? Some critters have lots of
Speaker 2: babies and hope a few survive. Others have just a
Speaker 2: few babies and take extra special care of them. What's
Speaker 2: the best strategy evolutionarily? Why do some critics choose one
Speaker 2: or the other? Does biology make any sense at all?
Speaker 2: Or does it just depend We'll dig into that on
Speaker 2: today's episode of Daniel and Kelly's Extraordinary Reproductive Universe.
Speaker 1: So on today's show, we're talking about the birds and
Speaker 1: the bees. So decide ahead of time if you think
Speaker 1: that's an appropriate topic for your children. Thanks for listening.
Speaker 2: Hi. I'm Daniel. I'm a particle physicist, and I have
Speaker 2: two kids so that neither of them have to be
Speaker 2: the middle child.
Speaker 1: Yeah. Hi, I'm Kelly wider Smith. I am a parasitologist.
Speaker 1: I have two kids because that's all I could handle.
Speaker 4: I'm Katie Golden. I host a podcast called Creature Feature.
Speaker 4: I have a dog so that she doesn't have to
Speaker 4: be a middle child.
Speaker 1: Katie, it's so great to have you on the show.
Speaker 3: Yeah, I'm so excited to be here.
Speaker 4: I too love parasites, by the way, so we've got
Speaker 4: that in common.
Speaker 1: I mean, that's the most important thing to have in common,
Speaker 1: I think.
Speaker 4: Yeah, that was what got me so into biology. Is
Speaker 4: a class I took. The official title of the class
Speaker 4: was like about mimicry, but the professor who ran the
Speaker 4: class was like so interested in parasites.
Speaker 3: That was basically all we talked about.
Speaker 4: And it's like he made the right call because that
Speaker 4: was super interesting, and it's like I love hearing about
Speaker 4: all these weird little freaks, and I gotta know more.
Speaker 2: What if it was a parasite that affected the host
Speaker 2: and made them interested in studying parasites.
Speaker 3: I'm probably chock full of that.
Speaker 1: Carl Zimmer's book Parasite Rex like changed my life. Yeah,
Speaker 1: it was going to be a parasitologist after reading.
Speaker 4: That, seeing the little isopod that's the parasite for fish,
Speaker 4: just like peeking out from a fishmouth, going like, hey
Speaker 4: U that altered my brain chemistry forever.
Speaker 1: It's pretty awesome. So I was talking to my friend
Speaker 1: Stacy Farina the other day and so the story with
Speaker 1: that isopod goes that it like eats the fish's tongue
Speaker 1: and replaces the tongue, and she studies fish like skeletal stuff,
Speaker 1: and she was like, you know, I've looked at a
Speaker 1: bunch of them and the tongue is still there. Guys, Yeah,
Speaker 1: what So I think they're actually just like clinging to
Speaker 1: the tongue and they're eating stuff, but they haven't really
Speaker 1: eaten the tongue, which I think is part of like
Speaker 1: what the pop side.
Speaker 4: Well, it's yeah, it's like the idea that they're now
Speaker 4: acting as the tongue. I thought they fed off of
Speaker 4: the blood supply, so they may cause some atrophying of
Speaker 4: the tongue, but it's not so much that they eat
Speaker 4: the whole tongue and then replace it. It's that they're
Speaker 4: stealing nutrients from the fish, and then when they leave
Speaker 4: the fish, usually the fish doesn't survive because it's basically
Speaker 4: mangled its tongue to the point where it can't use
Speaker 4: it as much anymore. That's my understanding. But also I
Speaker 4: think we have a fairly poor understanding of them because
Speaker 4: it's not every day that you find these little guy
Speaker 4: because you'd have to just like open up a bunch
Speaker 4: of fish mouths of like, let me see inside your
Speaker 4: mouth what you got in there?
Speaker 1: You know all the best stories, Katie, I look in
Speaker 1: a lot of fish mouths.
Speaker 2: And that's why we invited Katie on the podcast today
Speaker 2: to talk to us about babies.
Speaker 4: Yes, which hard to segue from fish mouths to babies.
Speaker 2: It's really hard to keep you guys on track. But
Speaker 2: I'm doing my best here.
Speaker 1: Well, I mean, what if we get the chance to
Speaker 1: talk about parasites, we will, But pulling back. So the
Speaker 1: reason we're talking about babies today is because we had
Speaker 1: a question from a listener, Nathan Ryan. He wanted to
Speaker 1: know about the benefits of having lots of babies relative
Speaker 1: to the benefits of just having a few, and so
Speaker 1: he was like, why would you ever have just a
Speaker 1: few when you could just flood the environment with babies?
Speaker 1: And ecological theory has a lot of ideas about that,
Speaker 1: and so I thought today we would talk about how
Speaker 1: many babies should you have?
Speaker 2: Thank you, Kelly for taking us back on on track
Speaker 2: and away from parasites, as difficult as that is for you.
Speaker 2: I love this question because in his email he specifically
Speaker 2: mentions the two kinds of strategies are strategy and case strategy,
Speaker 2: which describe having lots or few babies. That's really cool
Speaker 2: because I'm excited whenever I see a theory in biology.
Speaker 2: What it's not just descriptive like naming the parts of
Speaker 2: the flower, but building a mathematical model to understand the
Speaker 2: dynamics and how it all works. See, even underneath biology
Speaker 2: there has to be math. So we're going to dig
Speaker 2: into this question by walking through a bunch of examples
Speaker 2: of extremes lots of babies, few babies, and then thinking
Speaker 2: about whether the current theory about our in case strategists
Speaker 2: is actually working or not.
Speaker 4: This is such a good question in both personal lives
Speaker 4: and in olationary biology.
Speaker 2: Do you think Nathan is considering whether to have like
Speaker 2: two or like fifty kids.
Speaker 1: You better be considering whether he wants two or fifty wives.
Speaker 1: If he's going to have that many kids. That's a
Speaker 1: complicated question.
Speaker 2: Well he could be you never know, right.
Speaker 1: Right, Yeah, No, that's a good point.
Speaker 2: What do you think is the maximum number of kids
Speaker 2: any individual human has ever had?
Speaker 3: Mm?
Speaker 2: Genghis Khan.
Speaker 4: You know, I wouldn't be surprised if some of those
Speaker 4: warlords just like did get around enough to have like
Speaker 4: one hundred kids, not by one person.
Speaker 3: That would be not possible, right, We all have limits,
Speaker 3: you know.
Speaker 4: I think a lot of that though, is probably them
Speaker 4: thinking they have one hundred kids, or it's like those
Speaker 4: are my kids too? And got news for you, buddy,
Speaker 4: Probably not.
Speaker 1: You don't always know. That's one of the benefits of
Speaker 1: being the woman.
Speaker 3: You can be sure usually in most circumstances.
Speaker 2: Yes, I remember reading that there was a woman in
Speaker 2: the seventeen hundreds who gave birth to sixty nine children.
Speaker 3: How would that even work?
Speaker 2: Because it's sixteen pairs of twins, seven sets of triplets,
Speaker 2: and four sets of.
Speaker 3: Quadruplets and she lived through all of it.
Speaker 2: Yeah, And sixty seven of the sixty nine survived. But
Speaker 2: this is from the seventeen hundreds, and it's sort of
Speaker 2: like story and not like, yeah, well documented.
Speaker 1: Yeah, that would be intense.
Speaker 4: I have a hard time believing that, maybe just because
Speaker 4: I simply don't want to believe it like that.
Speaker 1: It boggles the mind, it does. Yeah, yeah, I don't
Speaker 1: think I want to believe it either. But let's jump
Speaker 1: into the main episode then. So we thought that first,
Speaker 1: if you're thinking about how many babies you should have,
Speaker 1: then you should think about how much energy it's going
Speaker 1: to take for each one of those babies from you.
Speaker 1: So how much energy is it going to take to
Speaker 1: protect and provision the young? And actually, we're not really
Speaker 1: talking about humans at all today. We're talking about non
Speaker 1: human animals. And so let's take a little walk through
Speaker 1: who does the care in different animals And so I'll
Speaker 1: start with fish. Actually, and fish, the males do a
Speaker 1: lot of the care. And you know, this is possible
Speaker 1: because most of the time eggs are put out into
Speaker 1: the environment and fertilization happens externally, and so you know,
Speaker 1: either one of them could be the one who splits.
Speaker 1: But for whatever reason, it's been the males who tend
Speaker 1: to so, for example small mouth bass and large mouth bass.
Speaker 1: The males will sort of use their fins to clear
Speaker 1: out an area, like a little depression where a nest
Speaker 1: will be, and then a female comes by, and if
Speaker 1: she decides the male sexy enough, she'll deposit some eggs,
Speaker 1: and then the male will deposit his sperm, and then
Speaker 1: it's his job to stay there and use his fins
Speaker 1: to aerate the eggs and make sure there's fresh water
Speaker 1: passing over them that through diffusion can like get into
Speaker 1: the eggs to keep those guys alive, and then also
Speaker 1: make sure that no predators eat those eggs, because they're
Speaker 1: amazing little balls of energy that would be great for
Speaker 1: like little minnows or crayfish. And so he's got to
Speaker 1: like defend the nest.
Speaker 2: Tasty little omelet of babies right there.
Speaker 1: That's right, that's right, pre made, and so I think
Speaker 1: it's pretty energetically expensive. They don't tend to eat, well,
Speaker 1: this is happening, and it's sort of not clear why,
Speaker 1: but maybe it's because they can't control themselves and they
Speaker 1: might eat the eggs. So anyway, they tend to not eat.
Speaker 1: It's a lot of work, but the males are doing
Speaker 1: most of the care, and so the eggs hatch, they
Speaker 1: swim up, and when they swim away, the male's job
Speaker 1: for the most part is done. He stays with them
Speaker 1: for a little while, but then they go off on
Speaker 1: their own. That's quite different than what happens with birds,
Speaker 1: right Katie.
Speaker 4: Yeah, I mean birds have a lot of different strategies.
Speaker 4: You have a lot of bird species where it's the
Speaker 4: female taking care of the offspring because she lays the eggs,
Speaker 4: and she of course has to keep the eggs warm
Speaker 4: under her body, so she stays with the nest. But
Speaker 4: you also have a lot of species of birds who
Speaker 4: work together, so you have a pair of parents, particularly
Speaker 4: in harsher environments, so sea birds in particular penguins obviously
Speaker 4: in their very harsh Antarctic environments. There are other species
Speaker 4: of penguins that live in warmer environments, but an amazing
Speaker 4: example is great hornbills. So they are a species of
Speaker 4: bird that go to extreme lengths to protect their eggs.
Speaker 4: The males actually will seal the females into a hollow
Speaker 4: inside a tree using his own feces, in her feces
Speaker 4: in a bit of mud to create sort of a
Speaker 4: plaster beautiful oh biology. Yeah, and then they leave a
Speaker 4: tiny hole and the male will go out and very
Speaker 4: devotedly bring back food for the female and then for
Speaker 4: the chicks once they hatch. And the reason that there's
Speaker 4: so much care in these situations of both parents working
Speaker 4: together is environmental stressors. So for the hornbills, it's in
Speaker 4: the places that they live in Southeast Asia. In these forests,
Speaker 4: there's a ton of predatory snakes who eat eggs, eat chicks,
Speaker 4: so so many arboreal snakes that creating sort of a
Speaker 4: sealed off, you know, bunker for the female and the
Speaker 4: eggs is really important. For seabirds, the there's a lot
Speaker 4: of kleptive parasites. Those are other birds that want to
Speaker 4: steal resources, including eggs, including eating chicks. It's just a
Speaker 4: very very harsh environment, particularly the ones that live in
Speaker 4: cold environments. So and also finding food is difficult. They
Speaker 4: have to leave the colony, go out to sea, go fishing,
Speaker 4: and so both parents need to kind of like switch
Speaker 4: off and alternate in terms of like taking care of.
Speaker 3: The egg, taking care of the chicks. If they didn't.
Speaker 4: Both put all of their effort into it, most likely
Speaker 4: their chicks wouldn't survive. And also just an interesting note.
Speaker 4: In species of birds where they're both working together as
Speaker 4: a pair, usually there's not as much sexual dimorphism, meaning
Speaker 4: like both of the male and the female look very similar. Also,
Speaker 4: when they're mating, both of them will often do some
Speaker 4: kind of mating display and try to impress the other
Speaker 4: mate equally because they're both putting in so much effort
Speaker 4: into the offspring, they're both equally trying to assess whether
Speaker 4: their mate is going to be good wears. In a
Speaker 4: lot of other species, where the female is the one
Speaker 4: doing most of the child rearing, it's the male that's
Speaker 4: trying to impress her because she's the one putting all
Speaker 4: of this investment into the offspring, Whereas the male is
Speaker 4: just kind of like going around sewing as wild out,
Speaker 4: so for him, he doesn't need to be as cheesy,
Speaker 4: where as the female needs to be really cheesy.
Speaker 2: So in this scenario where the female gets sealed in
Speaker 2: with the eggs and cares for them, do you think
Speaker 2: she's like into that or is she like tracked in
Speaker 2: like a slave in his like weird poo palace that
Speaker 2: he builds for her.
Speaker 3: She's into it.
Speaker 4: She can actually kind of kool aid man break out
Speaker 4: anytime she wants, but she's in there, and as long
Speaker 4: as the male comes and like feeds her, she will
Speaker 4: stay there with the eggs take care of them. If
Speaker 4: the male stops feeding her, I think she will break
Speaker 4: out and leave the eggs. And so there's a mutually
Speaker 4: bit official investment there, like the male coming back to
Speaker 4: feed her. Usually the male would only not come back
Speaker 4: if he came to some devastating ends. So the female
Speaker 4: completely cooperates and that she actually helps build the wall
Speaker 4: as well. So it's not like not a casko of
Speaker 4: a mantiato, but with porn bills.
Speaker 2: How would you have felt, Kelly, if you've been sealed
Speaker 2: into a room with your babies by your husband's poop.
Speaker 1: I mean, our house is pretty messy when we first
Speaker 1: had our kids. I don't know how different that was,
Speaker 1: and the diapers were piling up. I guess it wasn't
Speaker 1: zac species, It's right. I think I would have left,
Speaker 1: even with young people in the houses.
Speaker 4: But he's getting you uber eats like all the time,
Speaker 4: so that's an important aspect of it.
Speaker 2: But so the big picture here is that we're seeing
Speaker 2: lots of different kinds of scenarios, different strategies in different scenarios,
Speaker 2: and so the idea is that they're responding to the
Speaker 2: different situations they're in by developing these different strategies.
Speaker 3: That's right.
Speaker 4: Also when you have major differences among different types of animals,
Speaker 4: so like, for instance, mammals, usually it's the female doing
Speaker 4: most of the caring for young and a big reason
Speaker 4: for that is lactation. So like mammals, mammary glands, mammals
Speaker 4: have this ability to lactate and feed their offspring and
Speaker 4: this is how they care for very young babies and
Speaker 4: so usually not always, this means that the female is
Speaker 4: the one doing the primary caregiving for the offspring. You
Speaker 4: do see this, of course in other types of animals,
Speaker 4: so like there's a type of limbless worm like amphibian
Speaker 4: called the sicilian, which actually has something akin to malk
Speaker 4: Some species have this like viscous fluid that it produces
Speaker 4: from its kloeca that the offspring feed from. Like some
Speaker 4: species they actually allow their offspring to sort of chew
Speaker 4: on some like thick nutritional skin that they have a
Speaker 4: little excess mom jerky. And in these situations, the mom
Speaker 4: actually offers parental care to the offspring. But also in mammals,
Speaker 4: another exception is that there's a lot of very social
Speaker 4: species of animals where there's both male and female parenting.
Speaker 4: I mean humans is an example. There's also alloparenting, which
Speaker 4: is when either loosely related or non related individuals take
Speaker 4: care of the offspring that is not directly theirs. That's
Speaker 4: like common in a lot of different mammalian species, and
Speaker 4: that culminates into a version of mammals that actually becomes
Speaker 4: somewhat more insect like like naked mole rats who have
Speaker 4: a use social system where they have a queen who reproduces,
Speaker 4: and everyone else is basically facilitating the queen's reproduction. So
Speaker 4: that's like an extreme example of mammals going more towards
Speaker 4: like a b ant colony type model.
Speaker 2: I've heard this story. I think it may be apocryphal,
Speaker 2: and I want to ask you that in humans, it's possible,
Speaker 2: though difficult, for males to lactate given the right circumstances.
Speaker 2: Is that true or not?
Speaker 3: It's true.
Speaker 4: It's basically like hormones will determine lactation, So if some
Speaker 4: men naturally will produce, some hormones that may actually cause
Speaker 4: them to do a little bit of lactation. And actually,
Speaker 4: if someone takes hormones, you can induce lactation, and so
Speaker 4: you know, yeah, I mean honestly, like the differences between say,
Speaker 4: like male and female phenotypes in humans is so guided
Speaker 4: by hormones that when those are either you know, you
Speaker 4: have atypical levels of them, or you introduce synthetic hormones,
Speaker 4: so you can completely alter the phenotypic representation that includes
Speaker 4: functions like lactation.
Speaker 2: Does that mean that males have mammary glands they're just.
Speaker 4: Not active, yes, yes, essentially, yeah, mind blown.
Speaker 3: Yeah, you've got nipples.
Speaker 2: You've got I was aware of the nipples. Thank you.
Speaker 3: Just making sure.
Speaker 2: Let's give Daniel a tour here.
Speaker 3: Of these things.
Speaker 4: Just call them my chest buttons. Yeah, the memory glands
Speaker 4: and then are very underdeveloped. But there are like cases
Speaker 4: with like genetic differences where some men will have larger
Speaker 4: breasts and larger memory glands and some men can lactate,
Speaker 4: and yeah, that can totally happen, but you know it's
Speaker 4: not necessarily going to be enough maybe to feed a baby.
Speaker 4: But hey, you know what, get whatever help you can
Speaker 4: is what I say, every drop probably counts.
Speaker 2: No, try, gentlemen out there. She's not the only one
Speaker 2: who has to wake up in the middle of the
Speaker 2: night to feed the baby.
Speaker 1: Yes, that's right. Humping is a great technology. Yes, so
Speaker 1: when birds they make that like crop milk, do the
Speaker 1: males do that? Tours, that's something that just the females do.
Speaker 4: Males can also make crop milk. I think it depends
Speaker 4: on the species, but yes, you do have a mutual
Speaker 4: ability a lot of species to make crop milk that
Speaker 4: is not necessarily tied to you know, just the females,
Speaker 4: but some animals do, like the sicilian that I mentioned,
Speaker 4: like that can be just the female. And probably the
Speaker 4: explanation for that is in a lot of species, basically,
Speaker 4: unless you're an asexually producing animal, it's the female who's
Speaker 4: going to be giving birth to the offspring. Or unless
Speaker 4: you are a sea horse, in which case there's like
Speaker 4: basically two birds right where the female lays the eggs
Speaker 4: and does develop inside the males and then he gives
Speaker 4: birth to the live offspring. So the reason that you
Speaker 4: will often have cases where once an animal develops sort
Speaker 4: of a tool for offering nutritional aid to their offspring
Speaker 4: that it will be female is because usually it's the
Speaker 4: female who gives birth to the offspring.
Speaker 1: Now, insects are heroes of mine because they don't do
Speaker 1: a lot of parental care. Now, Katy, can you tell
Speaker 1: us about those?
Speaker 4: So later we're going to talk a little bit about
Speaker 4: R and K selection and just very briefly, our selection
Speaker 4: being you have a ton of offspring, you know, a
Speaker 4: bunch of cheaply made offspring, and K selection being you
Speaker 4: have maybe one or two really high quality offspring. It's
Speaker 4: very much an over generalization, but we'll get into the
Speaker 4: details later, but insects are sort of like the absolute
Speaker 4: champions of our selection, popping out enormous numbers of babies
Speaker 4: and just highly expendable babies.
Speaker 2: Either love them or you have lots of them, right,
Speaker 2: these are the two options.
Speaker 4: Well, essentially, it's a little more complicated than that, but yes,
Speaker 4: that is like sort of the basic idea behind it,
Speaker 4: and parental care is really rare in both insects and arthropods.
Speaker 4: So there are some notable exceptions such as like, usually
Speaker 4: it's the female again for the reason that I said,
Speaker 4: which is the female that lays eggs or gives birth
Speaker 4: to offspring, so scorpions will carry their young on their back.
Speaker 4: Centipedes will kind of curl up in this cute little
Speaker 4: nest like cradle for her offspring, which it's very adorable.
Speaker 4: There are even types of spiders like the desert spider
Speaker 4: who basically once she lays her eggs, she starts to
Speaker 4: digest her own insides and then will regurgitate her own
Speaker 4: juices for her offspring to feed on. And she does
Speaker 4: not survive this process. She turns herself into like a
Speaker 4: mom smoothie and then.
Speaker 3: Allows her offspring to eat her.
Speaker 4: It's called matrophagi eating one's mother, and the babies will
Speaker 4: eat like ninety five percent of her biomouse.
Speaker 1: You know, it's not cool. There's no petrophage or why
Speaker 1: are there no dad's getting.
Speaker 4: Eat there's probably some dads getting eaten, but yeah. The
Speaker 4: reason that it's usually matrophagi is because of the fact
Speaker 4: that usually it's the mother that gives birth or lays
Speaker 4: the eggs.
Speaker 3: But there are some very rare.
Speaker 4: Examples of both the mother and the father and insects
Speaker 4: taking care of their offspring. The only example I can
Speaker 4: think of there may be more, but this one is
Speaker 4: also really cool is burying beetles. So these are beetles
Speaker 4: that will find the carcass of some small animal and
Speaker 4: then we'll bury it. And the reason they do this
Speaker 4: is so that they can lay their eggs on a
Speaker 4: source of food, so they bury it to keep it
Speaker 4: away from other competitors, and then they lay their offspring
Speaker 4: in this sort of like little den of rotting meat.
Speaker 4: And then they actually will stay. Both the mother and
Speaker 4: the father bearing beetle will stay and protect their offspring,
Speaker 4: so they'll maintain the larder, make sure they have plenty
Speaker 4: to eat, and then they'll fight off competition and predators
Speaker 4: until the larva pupate into their more adult forms.
Speaker 3: So that's super rare.
Speaker 4: It just doesn't happen very frequently in insects or in
Speaker 4: arthropods because their usual techniques just have a huge amount
Speaker 4: of offspring, and statistically a lot of them are gonna
Speaker 4: make it.
Speaker 1: So I think any of the moms or dads out
Speaker 1: there are probably feeling a little bit better about what
Speaker 1: we went through when our kids were young right now
Speaker 1: after hearing about the insect examples. But let's go ahead
Speaker 1: and take a break, and when we get back we'll
Speaker 1: talk a bit more. About the costs associated with having babies,
Speaker 1: and we're back. So we've gone through and we've talked
Speaker 1: about the different in ways that the responsibility of taking
Speaker 1: care of the kids tends to be divided up in
Speaker 1: the animal kingdom. So now we're going to dig into
Speaker 1: some examples of it being costly to have offspring. And
Speaker 1: I think for most of us who have had kids
Speaker 1: were like, yes, of course it's costly to have offspring.
Speaker 1: Like a bunch of us moms lost weight while we
Speaker 1: were breastfeeding because it's calorically expensive and you're not sleeping,
Speaker 1: and you know it's obviously costly. But that's true for animals,
Speaker 1: not just humans. And there are some really nice examples
Speaker 1: of this. So, for example, David Lack did this long
Speaker 1: term study of these birds called great tits Paris major
Speaker 1: and confession, I didn't realize this was a bird species
Speaker 1: the first time I heard about these and a person
Speaker 1: who ended up being my PhD advisor started talking to
Speaker 1: me about great tits and I just had a like
Speaker 1: deer in the headlights moment, and it took me a second.
Speaker 1: He said something about eggs and I was like, ah,
Speaker 1: I think we're talking about birds or fish. And eventually.
Speaker 4: The first time I heard about great tits was when
Speaker 4: I was on a bird watching expedition with the bunch
Speaker 4: of senior citizens when I was in high school, and
Speaker 4: this sweet little old lady leaned over to me and says,
Speaker 4: now you have younger ears, so see if you can
Speaker 4: hear some great tits.
Speaker 1: That doesn't make any sense to.
Speaker 2: Place sound life, Yeah.
Speaker 4: Yeah, keep your eyes peeled for great tits. Just coming
Speaker 4: from this octagenarian. It was a wonderful moment.
Speaker 2: She's probably seen a lot, she knows right, it's.
Speaker 3: Nothing you ain't seen before.
Speaker 1: Maybe we should put a little warning at the top
Speaker 1: of this episode.
Speaker 2: But more broadly, like, we're hearing these examples about like
Speaker 2: different strategies, males taking care of the babies, females taking
Speaker 2: care of the babies. What do we learn sort of
Speaker 2: broadly from these examples, Like are there obvious trends here
Speaker 2: where people respond in certain ways to certain circumstances or
Speaker 2: is it just like a scattering of examples And the
Speaker 2: answer is it all depends.
Speaker 4: There are patterns, for sure. There have been attempts to
Speaker 4: kind of put the patterns into much more simple mathematical equations,
Speaker 4: which sometimes work but then sometimes they fail. But in
Speaker 4: general there are patterns. But because there are so many
Speaker 4: essentially factors that are a component in these evolutionary quote
Speaker 4: unquote choices, it can be difficult to see the pattern
Speaker 4: from the noise, but they do exist, and there have
Speaker 4: been some like observable patterns that have been found that
Speaker 4: can kind of help sway the decision in terms of
Speaker 4: like what type of offspring strategy species end up falling into, right, Kelly.
Speaker 1: Yeah, so we are essentially making the argument that it
Speaker 1: depends today, which Daniel will not be surprised to hear.
Speaker 1: So I found this quote from a textbook that I
Speaker 1: used in grad school, and it's the evolution of care
Speaker 1: behavior is complex, and we are still far from fully
Speaker 1: understanding which factors really influence the evolution of care in
Speaker 1: both males and females. Models are arguments like the ones
Speaker 1: presented above in this textbook may also prove too simple
Speaker 1: because they generally consider just a few factors at a time.
Speaker 1: So we're talking today some of the different solutions that
Speaker 1: evolution has landed on and some of the different factors
Speaker 1: that influence the decisions that end up getting made over
Speaker 1: evolutionary time. But it really does depend Life.
Speaker 2: Is messy and lots of factors must come into play,
Speaker 2: predation and environment and variability and all sorts of crazy stuff.
Speaker 2: It'd be amazing if you could boil it down to
Speaker 2: just a few variables like you can in physics. I
Speaker 2: don't know why physics ever works, frankly.
Speaker 1: So yeah, we're going to talk about a lot of variability,
Speaker 1: and then we're going to narrow down a little bit
Speaker 1: on one attempt to sort of summarize what we see
Speaker 1: and why we see it. And then we're going to
Speaker 1: talk about how that sort of way of summarizing things
Speaker 1: fell apart, and how now we're back to trying to
Speaker 1: find more complicated models that include more variable.
Speaker 2: All right, now I'm ready to talk about great tits.
Speaker 1: That's great.
Speaker 4: It's always good to get into the math before we
Speaker 4: start talking about great that's right.
Speaker 1: That's right. That's how most of these conversations work out.
Speaker 1: So there's this researcher in England. Great tits are these
Speaker 1: tiny little birds, and there's this population that's been monitored
Speaker 1: for decades and all of the birds, or as many
Speaker 1: as possible, are caught every year they're banded. And then
Speaker 1: you look to see who's coming back year after year.
Speaker 1: These birds tend to lay one set at one clutch
Speaker 1: of eggs once a year, and the army of graduate
Speaker 1: students who were working on this for decades would go
Speaker 1: out and they would count how many eggs. They would
Speaker 1: weigh the birds soon after they hatched, and then they'd
Speaker 1: measure survival by determining who came back. And they were
Speaker 1: looking at a large enough area that I think they
Speaker 1: decided that, you know, the birds who flew to join
Speaker 1: a different population. That was a negligible number of birds,
Speaker 1: so they pretty much were keeping track of everybody. And
Speaker 1: they noticed that these birds usually lay eight or nine eggs,
Speaker 1: and that the more eggs there were in a nest,
Speaker 1: the smaller the offspring would be. And you could test
Speaker 1: this by moving eggs between nests and looking to see
Speaker 1: if you like, make the parents feed more offspring, What
Speaker 1: does that do to the size of the birds and
Speaker 1: the parents are out from like dusk to dawn, gone
Speaker 1: to dusk, that would be it from done to dusk.
Speaker 3: Trying depending on how you look at it.
Speaker 2: Yeah, they depends whether drinking, yeah.
Speaker 1: Right, drinking caterpillar juice or something yummy. And they found
Speaker 1: that the more birds they had to feed, the smaller
Speaker 1: the birds were, and then if you look at those
Speaker 1: small birds, they're less likely to survive and show up
Speaker 1: again in the population as adults. So if you have
Speaker 1: too many babies, those babies don't seem to make it,
Speaker 1: and you've expended all of that energy for nothing. But
Speaker 1: they did some like mathematical modeling and moving some eggs around,
Speaker 1: and they ended up deciding like, okay, but it looks
Speaker 1: like the birds are producing fewer eggs than we think
Speaker 1: that they could be producing optimally every year that they
Speaker 1: could feed enough and enough of them could come back
Speaker 1: in the future. Why aren't they making more eggs? And
Speaker 1: the idea here was that you're not just trying to
Speaker 1: maximize the number of eggs that you're producing in one year.
Speaker 1: You're thinking about your lifetime reproductive success. So if you
Speaker 1: go all out and you raise as many eggs this
Speaker 1: year as you can, probably gonna exhaust yourself and not
Speaker 1: be able to survive until the next year so that
Speaker 1: you can have more offspring. And to be honest, because
Speaker 1: ecology is complicated, as far as I know, they didn't
Speaker 1: find good evidence for that in this system, but they
Speaker 1: have found evidence for that in other systems, so like
Speaker 1: in European kestrels, so these are birds that are predators
Speaker 1: and they pick off little mammals. They found that if
Speaker 1: you put extra eggs in a nest and like those
Speaker 1: adults had to feed more babies, the babies were less
Speaker 1: likely to survive to adults, and the adults who had
Speaker 1: more babies in their nest were less likely to show
Speaker 1: up the next year, so they were less likely to
Speaker 1: survive the winter.
Speaker 4: It just sounds though, like they instead of like showing up.
Speaker 4: I know what you mean is their survival rates, but
Speaker 4: it does kind of sound like when you gave them
Speaker 4: too many kids.
Speaker 3: They're like, that's it. I'm out, I'm leaving done.
Speaker 1: That's right, I'm gonna go become a dancer. I'm done.
Speaker 1: But you know this is ecology, right, So the answer
Speaker 1: has to be it depends. And even though you feel
Speaker 1: like you have a nice model, nice theory for understanding
Speaker 1: how this stuff works, if you look in a different system,
Speaker 1: you don't always find support. So David Resnick studies guppies.
Speaker 1: These are these tiny little fish that you find in Trinidad,
Speaker 1: and he took them into I think this was a
Speaker 1: lab study, and he compared the females who were paired
Speaker 1: with a male and could mate to females who didn't
Speaker 1: have a male. And the idea was supposed to be
Speaker 1: that the females who had to produce young would end
Speaker 1: up weighing less because it's energetically expensive than the females
Speaker 1: who didn't have to produce young. But they didn't find
Speaker 1: that the females who had to produce babies just ate more.
Speaker 1: That's what I did for sure, and so they ended
Speaker 1: up being in just as good shape. And so you know,
Speaker 1: this kind of stuff can depend on like how many
Speaker 1: resources are available in the environment. Like if you're feeding
Speaker 1: baby chicks, but it's a year where there's just loads
Speaker 1: of insects, maybe it's one of those years where the
Speaker 1: cicadas come out of the ground and there's just food everywhere,
Speaker 1: then you know you don't have as many trade offs.
Speaker 2: So if you can just sit on the couch and
Speaker 2: eat Ben and Jerry's, then you should have lots of kids.
Speaker 1: And so they quote from earlier is about how there's
Speaker 1: lots of other factors to consider.
Speaker 2: Flavors of Ben and Jerry's are available. This kind of stuff.
Speaker 4: People often ask like can I feed, say, wild birds,
Speaker 4: and the answers It depends again because one of the
Speaker 4: problems if you feed wild birds too much, you actually
Speaker 4: give them a false sense of security in terms of like, oh,
Speaker 4: there's a lot of plenty, I can have a lot
Speaker 4: of babies, and then they end up having more babies earlier,
Speaker 4: and then they might miss key points in terms of
Speaker 4: like some species maybe time their offspring to the emergence
Speaker 4: of certain insects, right, like they follow the breeding cycle
Speaker 4: of caterpillars or other insects, and then they may if
Speaker 4: you give them too many resources artificially, they may actually
Speaker 4: have more offspring earlier, and then when they migrate, right,
Speaker 4: they don't stay in your backyard forever. Then they migrate,
Speaker 4: and then they don't actually have the resources that they
Speaker 4: kind of were led to believe they would have. It
Speaker 4: can actually cause a population crash. So like there's a
Speaker 4: lot of like weird unexpected consequences is where a lot
Speaker 4: of species have this kind of like timing system, and
Speaker 4: they can also kind of they can change their breeding
Speaker 4: behavior based on the stress and the resources that they
Speaker 4: have available to them.
Speaker 2: What if you feed wild birds, but you do it consistently.
Speaker 2: You don't just like yanke it away from them.
Speaker 4: Well, it depends, like if they migrate, then you'd have
Speaker 4: to follow them. It's like, all right, where are you going?
Speaker 3: Get on a plane?
Speaker 1: You tag them and migrate with them.
Speaker 4: And if you're just feeding birds consistently and they stay
Speaker 4: in your backyard, that's how we got chickens.
Speaker 2: That's not so bad, that's delicious.
Speaker 1: You can also transmit diseases at feeders, Yeah, that's true.
Speaker 1: It had been like fifteen minutes since we had talked
Speaker 1: about parasites, so I had to pull that back.
Speaker 4: When you have a really crowded public feeder, you've got
Speaker 4: a lot of birds, you know, rubbing up against each other,
Speaker 4: so then they can transfer diseases. So like, especially when
Speaker 4: there's like avian flu going around, it's probably not a
Speaker 4: good time to take in those feeders.
Speaker 2: We had a bird feeder our backyard and there was
Speaker 2: a blue jay in the neighborhood and who really liked
Speaker 2: like the bigger seeds. I think it was the some
Speaker 2: flower seeds. He was also a bully, so he would
Speaker 2: like chase away all the other birds and then he
Speaker 2: would sift through and just like throwing seeds left and
Speaker 2: right to get to the some flower seeds and gobble
Speaker 2: them up, but making a mess everywhere, and all the
Speaker 2: other birds were scared. We had to like try to
Speaker 2: chase this guy away.
Speaker 1: Yeah, we have a family member like that. We stopped
Speaker 1: inviting them to say. So, we've talked about a variety
Speaker 1: of different ways that nature has sort of solved the
Speaker 1: problem of who takes care of the offspring? How many
Speaker 1: offspring do you have? But sometimes it's complicated, So let's
Speaker 1: move on to this idea of R and K strategists.
Speaker 1: So this idea was meant to sort of come up
Speaker 1: with a theory that would explain why sometimes you get
Speaker 1: organisms species that make loads of offspring and then other
Speaker 1: times you get species that just make a few offspring.
Speaker 1: So what kind of conditions would promote doing something crazy
Speaker 1: like having thousands of offspring? So the idea here is
Speaker 1: that maybe you have some environments that are just changing
Speaker 1: all the time. They're unpredictable. Maybe like periodically fires come
Speaker 1: through and they just sort of devastate the environment. And
Speaker 1: so it's not necessarily that like resources are limited. It's
Speaker 1: just every once in a while something catastrophic happens and
Speaker 1: in that case, as the theory went, the idea is
Speaker 1: that you should produce loads of offspring, and you should
Speaker 1: start producing these offspring as young as you can, so
Speaker 1: that you can get as many chances at making offspring
Speaker 1: as possible, and that you can fill any new niche
Speaker 1: that opens up by having all of these new offspring. Whereas,
Speaker 1: if you're in an environment where there's a set number
Speaker 1: of resources, that environment is pretty stable, it's pretty predictable,
Speaker 1: then you should invest in making a few number of
Speaker 1: offspring that are in really great shape and they're really
Speaker 1: good competitors because there's going to be a lot of
Speaker 1: competition for those resources since everybody's sort of at the
Speaker 1: limits of what the environment can handle in terms of
Speaker 1: the amount of resources that are available there for everybody.
Speaker 2: Does that make sense to you? I mean, I try
Speaker 2: to imagine myself as a parent in this circumstance, and
Speaker 2: like it seems like that makes sense under the assumption
Speaker 2: that you can do nothing to help your kids survive, Right,
Speaker 2: you should just have lots of them because it's all random.
Speaker 2: But I'm imagining, like if I have kids in suburban
Speaker 2: southern California where things are pretty stable, versus I have
Speaker 2: kids in like post apocalyptic Mad Max scenario, Like, am
Speaker 2: I going to pump out one hundred kids and then
Speaker 2: just like let them run crazy free and hope they survive?
Speaker 2: It feels to me like I'd still be better off
Speaker 2: having few kids and trying to like navigate them through
Speaker 2: the chaos.
Speaker 1: Well, evolution has selected our species over time to be
Speaker 1: really good at making a small number of offspring, and
Speaker 1: you can use our intelligence to sort of help them
Speaker 1: survive in this complicated environment. I would say that we
Speaker 1: don't necessarily have the ability at this point to make
Speaker 1: as many offspring as it would take. To think of
Speaker 1: yourself as an R strategist, what's your take on this, Katie.
Speaker 4: Yeah, I mean I think it's kind of comes down
Speaker 4: to probably very complicated statistical probabilities that I have no
Speaker 4: way of kind of conceptualizing. But you know, it's sort
Speaker 4: of like a I'm going to make a stock market comparison,
Speaker 4: but I want to make it clear I don't know
Speaker 4: anything about investment. But if you have like a really
Speaker 4: risky market, right, like you diversify your portfolio in general, right,
Speaker 4: Whereas maybe if you have it more stable market, It's like, man,
Speaker 4: I know that everybody loves apple juice, so I'll keep
Speaker 4: investing in apple juice. I don't mess around with the
Speaker 4: stock market because I truly don't understand it.
Speaker 2: I don't think apple juice is a growth industry. Katie's
Speaker 2: not an investment. Don't take advice from Katie, folks.
Speaker 4: If I drink enough, it's a growth industry for me.
Speaker 4: But like, one thing is that you can think of
Speaker 4: it in terms of like an individual's success, right, Like
Speaker 4: I'm a parent, I can like make sure my child
Speaker 4: reaches adulthood. But you can also look at it in
Speaker 4: terms of just like the spread of a bunch of genes.
Speaker 3: And there have been.
Speaker 4: Some sort of like back and forth arguments about like
Speaker 4: what matters more genes or phenotype, right, but in general,
Speaker 4: like sometimes you may have a situation in which having
Speaker 4: a ton of offspring and not taking care of them
Speaker 4: but just leaving it up to chance is the best strategy,
Speaker 4: even if, like you say, take care of your offspring,
Speaker 4: because say there's a disease that comes around, Like, no
Speaker 4: matter how good you take care of your offspring, a
Speaker 4: disease that comes hit you, there's nothing you can do
Speaker 4: about that.
Speaker 3: But if you have fifty.
Speaker 4: Thousand offspring and one or two of them have a
Speaker 4: genetic mutation where they manage to avoid this like devastating disease.
Speaker 4: Then your genes get passed on and it doesn't matter
Speaker 4: that you were a terrible parent hypothetically, But of course
Speaker 4: obviously we do have all kinds of parenting right in nature,
Speaker 4: and so it does mean that there have been stable
Speaker 4: patterns of both our and case strategists being.
Speaker 3: Able to survive.
Speaker 4: But it's just that there isn't one single strategy that
Speaker 4: always wins. The species that we see alive today have
Speaker 4: not been raining the earth for the past, you know,
Speaker 4: millions of years, Like, so many species have gone extinct
Speaker 4: or have turned into a different species that survived to today.
Speaker 4: So like there's a lot of strategies that were tried
Speaker 4: and then then failed, and then a little different strategy
Speaker 4: was tried and failed. So it's really just about cannas.
Speaker 4: Species find an amount of stability for a certain chunk
Speaker 4: of time, and then that lasts for some amount of time,
Speaker 4: and there's no guarantee that any of the current survivors
Speaker 4: now are going to last the next million years.
Speaker 2: I think it's interesting that you talk about like good
Speaker 2: parenting and bad parenting. It's funny to put these sort
Speaker 2: of like moral labels on it, and we joke a
Speaker 2: little bit, but you know, it makes me wonder if
Speaker 2: you're the parent in a species where you just sort
Speaker 2: of like make a lot of them and spraym into
Speaker 2: the environment and ignore them, do you still love your
Speaker 2: babies or is it just like not a bigger part
Speaker 2: of your life.
Speaker 3: Sometimes you eat them, sometimes you eat them, sometimes you
Speaker 3: eat them.
Speaker 2: You love them for dinner.
Speaker 4: There are a lot of like amphibians and fish that
Speaker 4: will sometimes eat some of their offspring just like it's
Speaker 4: fine if I nibble on a few of them, right,
Speaker 4: But again, it's not because they're cruel. It's because of
Speaker 4: the trade off between your own personal survival and health
Speaker 4: and being able to bear future offspring and your offspring
Speaker 4: surviving in fact, like there are some species of animals
Speaker 4: that will like fight to the death to protect their offspring,
Speaker 4: Like I've seen elk try to stomp the dickens out
Speaker 4: of a mountain lion to save her offspring. Whereas some
Speaker 4: animals who have a higher fecundity, like they see a
Speaker 4: predator and they're like, all right, I'm out because I
Speaker 4: can have babies in the future.
Speaker 1: Well, we have hit optimum dKu episode here because we've
Speaker 1: talked about poop and cannibalism. But we're still going to
Speaker 1: go ahead and do one more session even though we've
Speaker 1: hit all the high points. So let's go ahead and
Speaker 1: take a break, and when we come back we will
Speaker 1: talk more about babies. Before the last break, Katie was
Speaker 1: talking about variability and parental care, how some animals are
Speaker 1: willing to risk their lives and some just aren't willing
Speaker 1: to risk their lives for their babies. One of the
Speaker 1: things that got me really excited about behavioral ecology was
Speaker 1: that even within species, there's a lot of variability, and
Speaker 1: trying to understand why some animals are great parents and
Speaker 1: some are kind of miserable is just fascinating to me.
Speaker 1: Like I studied small mouth bass for a while, and
Speaker 1: after the ice would melt off the lakes in Wisconsin,
Speaker 1: it was still absolutely frigid. We would jump in and
Speaker 1: we would try to find every nest in this northern
Speaker 1: Wisconsin lake and some of the males you would approach
Speaker 1: their nest and you could see just like the sh
Speaker 1: sho of them as they ran off and the minnows
Speaker 1: would come in and they'd try to eat their eggs
Speaker 1: and you just would never see that mail again. And
Speaker 1: then there were other males who you'd be like trying
Speaker 1: to figure out where the nest is, you haven't even
Speaker 1: located it yet, and they would literally like torpedo you
Speaker 1: in the face and knock your mask off and like,
Speaker 1: you know, knock your snorkel out of your mouth, and
Speaker 1: they would just keep like ramming into you. So even
Speaker 1: within species, there's loads of differences, and I don't think
Speaker 1: we understand very well what those differences are. Sometimes it
Speaker 1: has to do with how big the males are. So like,
Speaker 1: if a male is huge and all of the predators
Speaker 1: in the lake have little mouths, then he can be
Speaker 1: pretty sure nothing's going to be able to eat him,
Speaker 1: so he might as well attack. Whereas if you're the
Speaker 1: little guy, maybe you don't get gutsy until you grow
Speaker 1: for a few more years, until you're big enough that
Speaker 1: probably nothing can eat you. But there's loads of variability
Speaker 1: even within species, which I think is just totally fascinating
Speaker 1: and adorable.
Speaker 4: I mean that reminds me of like sort of different
Speaker 4: mating strategies where you have sort of sneaky males versus
Speaker 4: large sort of job males, like in salmon and coho salmon,
Speaker 4: like there's the jacks, which are the little guys, and
Speaker 4: then the hook noses, i think based on the shape
Speaker 4: of their face, which are the bigger ones. And the
Speaker 4: little guys actually do a really good job of sneakily
Speaker 4: mating with females, whereas the big guys they may have
Speaker 4: a more like secure position in terms of not being
Speaker 4: preyed upon, but they're less agile, and actually the jacks
Speaker 4: tend to be more numerous because what happens is the
Speaker 4: female will depositor eggs and the jack kind of like
Speaker 4: zoom out there and puts the sperm on the eggs
Speaker 4: and then zooms away right like an.
Speaker 3: Egg assass and just like boop, like fertilized.
Speaker 4: But yeah, it's also like even a single individual can
Speaker 4: change their strategy based on say, environmental stressors like kangaroos
Speaker 4: and wallabies can basically control when they have offspring. It's
Speaker 4: called embryonic diapause. So it's like when they freeze the
Speaker 4: development of their embryo when they feel like stressed or
Speaker 4: like the conditions aren't right, so they're controlling their fecundity.
Speaker 4: There's also what we mentioned earlier about cannibalism, like eating
Speaker 4: your eggs, eating your offspring when resources seem limited or
Speaker 4: when you're stressed out, like bears will sometimes do that,
Speaker 4: Like bears will eat their newly born offspring like black bears,
Speaker 4: and it's like, well, why would they do that, Well,
Speaker 4: if it's a weaker offspring, or if they're stressed out
Speaker 4: and they feel like resources aren't good at that time,
Speaker 4: they actually control whether or not they want to invest
Speaker 4: in an offspring at that point.
Speaker 1: Tough decisions. Our kids don't know how lucky they are
Speaker 1: to have made it as far as they did that
Speaker 1: we never snacked them right, even when things were scary.
Speaker 4: They think it's terrible when parents eat their chocolate bunnies,
Speaker 4: and they don't know it could be so much.
Speaker 1: Worse, so much worse. I'm gonna have to tell my
Speaker 1: kids that around here. Yeah, it'll be good. I'm a
Speaker 1: great parent. So to get back to RNK strategists, so
Speaker 1: we have kind of given some examples of different rn
Speaker 1: K strategists over the course of this chat, Haiti mentioned
Speaker 1: that insects are the classic R strategists and just like
Speaker 1: a funny aside. I could never remember if the rs
Speaker 1: and the k's, which one was the fast and lots
Speaker 1: of babies and which one was the slow and just
Speaker 1: a few babies. And this morning, my really embarrassing way
Speaker 1: of remembering was Kelly starts with K and I only
Speaker 1: had a few babies. And so anyway, anyone needs to
Speaker 1: remember that in the future, just think about Kelly only
Speaker 1: had two babies. But anyway, that was also my way
Speaker 1: of remembering if I was going to Slovakia or Slovenia
Speaker 1: to give a talk, Slovakia has a K in it
Speaker 1: and Kelly's going.
Speaker 4: I remember it with a rapid fire for our and
Speaker 4: quality with K because I'm good at spelling.
Speaker 3: I love it.
Speaker 1: Okay, so you and our notes have a really great
Speaker 1: explanation of whale parental care. Do you want to chat
Speaker 1: about them as like ideal K specialists?
Speaker 3: Yeah? Absolutely so.
Speaker 4: Whales are, especially the largest whales. Blue whales are an
Speaker 4: excellent example of K strategists, right like they fit into
Speaker 4: the classical. They're big, they live a long time, they're intelligent,
Speaker 4: and they have a very long gestation period of about
Speaker 4: a year, and they only have an offspring every presidential
Speaker 4: term essentially like every four years or so. So they
Speaker 4: are very slow in terms of producing a lot of offspring,
Speaker 4: but they pour a huge amount of resources into the offspring.
Speaker 4: They produce about fifty gallons of milk per day.
Speaker 2: That's incredible.
Speaker 4: Yeah, it's also really high quality milk. It's very very
Speaker 4: fat dense.
Speaker 2: Is it delicious?
Speaker 3: You know?
Speaker 4: I would love to try some hot fresh whale milk.
Speaker 4: That sounds very good, especially because we know what their
Speaker 4: diet is, Like a ton of krill that's got to
Speaker 4: have a nice fishy aftertaste.
Speaker 2: Wait, how big is a blue whale nipple? I mean,
Speaker 2: could a human even actually like get it fresh from
Speaker 2: the whale?
Speaker 4: You know, I've actually never seen a blue whale nipple,
Speaker 4: so I don't know. I'm gonna assume it's pretty big.
Speaker 2: If I google that, am I going to get on
Speaker 2: some terrorists watch list? Right now? You know?
Speaker 4: I did once google elephant breasts, and I'm sure I'm
Speaker 4: on a list. Oh no, But I meant literally elephant
Speaker 4: breast because I was curious about breastfeeding and elephants.
Speaker 3: And I can't explain everything.
Speaker 2: Since we're on the topic of Katie's weird history, what
Speaker 2: is the most interesting animal whose milk you have had?
Speaker 3: Oh? I mean, I think just goat milk.
Speaker 4: I'm not very exciting. I haven't done anything too adventurous.
Speaker 4: I wish I could say, like I've suckled on a
Speaker 4: sicilian or something, but no, I really haven't.
Speaker 3: Oh, goat milk. I guess human milk though.
Speaker 2: Right, milk is pretty weird.
Speaker 3: Human milk's pretty weird, but we all drink it as babies.
Speaker 2: I lived in a small village in France where the
Speaker 2: grocery store had pony milk available, Yes, little bottles of
Speaker 2: pony milk.
Speaker 3: Like from specifically ponies. Like, okay, why not?
Speaker 2: I was.
Speaker 3: Really it wasn't very good.
Speaker 2: It was too horsy for me.
Speaker 3: Yeah, okay.
Speaker 2: You know how a milk sort of reminds you of
Speaker 2: the odor of an animal, like goats, so it tastes
Speaker 2: like the way goats smells a little bit. Not a
Speaker 2: fan of the way horses smell.
Speaker 4: I feel that I definitely can only handle a certain
Speaker 4: amount of goat cheese before I'm like, I feel like
Speaker 4: I'm eating the smell of the.
Speaker 2: Goat exactly, like I'm licking a sweaty gat or something.
Speaker 1: Yeah, it smells and tastes like hay to me, and
Speaker 1: I love it. But anyway, let's get back.
Speaker 4: To blue whales all right, So blue whale milk probably
Speaker 4: tastes like blue whale, and the calves actually gain hundreds
Speaker 4: of pounds of weigh every few days.
Speaker 2: Incredible.
Speaker 4: They grow at an incredible way. They go from being
Speaker 4: about the sights of like a shipping container to like
Speaker 4: nearly a football field, right, So it's wild. It's a
Speaker 4: wild amount of growth. So this also highlights sort of
Speaker 4: the interesting trade off between somatic growth, meaning growing yourself
Speaker 4: and growing your offspring. Whales spend their first parts of
Speaker 4: their lives just grow, growing themselves to enormous sizes by
Speaker 4: drinking a huge amount of their mother's milk, and then
Speaker 4: when they're old enough, they start to filter feed on krill.
Speaker 4: They're balen whales. They have those bristle structures in their mouths.
Speaker 4: They take in huge amounts of sea water and then
Speaker 4: expel it all out, and then krill, which are hugely
Speaker 4: inbundant of a huge source of biomass, get caught in
Speaker 4: their bileen and then they can swallow that and just
Speaker 4: they eat. They're like vacuums that are able to exploit
Speaker 4: a massive amount of biomass in the ocean. It'd be
Speaker 4: like a cow on land that's just giant and had
Speaker 4: like a giant sort of like lawn mower mouth that
Speaker 4: could go and like mow an entire field and like
Speaker 4: a few hours.
Speaker 1: Why hasn't evolution come up with that yet?
Speaker 3: It's coming.
Speaker 4: Giant, terrifying cows are coming, I'm sure, and they'll be
Speaker 4: shaped like crabs based on other patterns in nature.
Speaker 1: But we just had an interview with the woman who
Speaker 1: wrote the review paper and how grumpy she is about
Speaker 1: how it's been interpreted. But anyway, crab episode coming soon.
Speaker 4: I stand firmly behind my crab carsonization of cow's theory.
Speaker 1: Excellent.
Speaker 4: But yeah, so after this period of growing the self
Speaker 4: to these enormous sizes, then they can enter into the
Speaker 4: reproductive period and then spend a lot of resources developing
Speaker 4: the offspring, taking a year to develop the embryo to
Speaker 4: becoming the live born offspring, and then just feeding it
Speaker 4: huge amounts. Basically, they inhabit this evolutionary niche where they
Speaker 4: invest their resources into being really big, and then when
Speaker 4: you give birth, your offspring has taken a whole year
Speaker 4: to develop inside your massive body. So there's very few
Speaker 4: predators who could actually target your offspring, and honestly, they
Speaker 4: had very little in terms of competitors and predators until
Speaker 4: humans figured out how to fashion a harpoon. And that
Speaker 4: we liked whale juices for a lot of disgusting use.
Speaker 2: Is that sounds like a title for a great book,
Speaker 2: Whale Juices for Disgusting uses.
Speaker 4: Whale Jesus for Disgusting uses a very highly unethical guide
Speaker 4: to using whale Ambergriss.
Speaker 1: Yeah, Okay, So we've talked about insects being amazing r strategists.
Speaker 1: We've now talked about blue whales being amazing case strategists.
Speaker 1: And now that you feel like maybe you've got this
Speaker 1: strategy in your mind, I'm going to go ahead and
Speaker 1: tell you that this probably does not represent reality because
Speaker 1: it's more of a spectrum when you look into these things,
Speaker 1: and it's, you know, not surprising that things don't fit
Speaker 1: into little categories because probably the only thing in an
Speaker 1: environment that matters isn't like how often a fire passes through.
Speaker 1: And so usually when you find species, you find some
Speaker 1: like combination of these different kinds of traits. So a
Speaker 1: classic example is an elm tree. So an elm tree
Speaker 1: is kind of like a case strategist in that it
Speaker 1: lives for a really, really really long time and it
Speaker 1: gets huge. And why it to get huge is because
Speaker 1: it is competing with the other trees in the canopy.
Speaker 1: And if you can't get to the top of the canopy,
Speaker 1: you don't get light and you don't get to survive.
Speaker 1: And Daniel, this sort of addresses your question earlier about like, well,
Speaker 1: why wouldn't you always just have a few offspring that
Speaker 1: you invest a lot in? So for these seeds, they
Speaker 1: make loads of seeds. I think they can make up
Speaker 1: to a million seeds in their lifetime. And these seeds
Speaker 1: are tiny, and the only way any of those seeds
Speaker 1: get to survive is if they happen to end up
Speaker 1: in a spot on the floor where they get really lucky,
Speaker 1: Like maybe a super old tree that's one hundred years
Speaker 1: old has finally fallen over and died, and now there's
Speaker 1: a little bit of light coming through the canopy making
Speaker 1: it to the forest floor, and your offspring just don't
Speaker 1: have any chance to survive unless they end up randomly
Speaker 1: in one of those spots.
Speaker 2: It's like waiting for a physics professor to retire and
Speaker 2: open up a professorship.
Speaker 1: Finally, right, or answer your emails.
Speaker 3: Yeah, it's completely random, Yes.
Speaker 1: Completely random, and so like if you had made five
Speaker 1: of the greatest acorns in the warld Oh, thank.
Speaker 2: You, My acorns are wonderful.
Speaker 3: Yes, okay, a lot of squirrel energy over here. I
Speaker 3: don't know why.
Speaker 1: Yeah, that's right.
Speaker 2: I'm just trying to imagine what is it like to
Speaker 2: be a good elm parent, Like you know, you're really
Speaker 2: craft these acorns, or dold you just care deeply about them,
Speaker 2: or you're like weirdly irrationally proud of your acorns. I
Speaker 2: don't know. I was trying to do it.
Speaker 1: And the promorphizing trees. I never could say that word
Speaker 1: without first stumbling and overthinking it. But also, if you
Speaker 1: make like giant seeds, they're gonna get eaten by squirrels,
Speaker 1: and so just for a variety of reasons, the best
Speaker 1: strategy is to make lots of them every year and
Speaker 1: scatter them as far as you can and not care
Speaker 1: and not care. It seems like there's really no better
Speaker 1: strategy than that, and the environment is selecting for that.
Speaker 4: An animal equivalent to the elm tree are actually a sunfish.
Speaker 4: They're huge, huge fish, like the size of a kiddie pool,
Speaker 4: and they're those weird guys that are kind of like
Speaker 4: flat and they've got the big eyeballs and they're really funny.
Speaker 4: But you would think, like, okay, there huge so that
Speaker 4: they can have large offspring that like nobody messes with.
Speaker 4: But actually their offspring are teeny teeny tiny. They're only
Speaker 4: a couple millimeters big. They're nearly like planktonic, and they
Speaker 4: have huge amounts of them. The females can lay like
Speaker 4: millions of eggs in her lifetime, and so it's kind
Speaker 4: of like the elm situation where they're just doing like
Speaker 4: I'm just gonna scatter a bunch of them. It's a
Speaker 4: little less clear why they do this versus the elm right,
Speaker 4: because it's not the same situation where the elm seeds
Speaker 4: need to find that perfect location where they don't have
Speaker 4: to compete with other trees to get sunlight through the canopy.
Speaker 4: But in the ocean you have a lot of evolutionary
Speaker 4: pressures where it's hard not to get eaten and the
Speaker 4: ocean and it also takes a lot of resources right
Speaker 4: to create a large offspring. So for these sunfish, even
Speaker 4: though it seems like they're going towards the blue whale
Speaker 4: strategy of like, hey they're big, right, so maybe it's
Speaker 4: so that they can just invest a lot in one offspring.
Speaker 4: No complete opposite, just a bunch of tiny babies that
Speaker 4: get eaten up like little popcorn and then like some
Speaker 4: of them though, happen to keep growing and growing and
Speaker 4: growing until they're just enormous.
Speaker 2: So, Kelly, if we think that the R strategy in
Speaker 2: case strategy is a little too simplistic, how we like
Speaker 2: upgraded our model to understand this in terms of like
Speaker 2: more variables, and it's sort of a higher dimensional evolutionary space.
Speaker 1: Yeah, so now we talk about life history strategies, and
Speaker 1: the decisions that animals make are things like when do
Speaker 1: you start breeding, how many times in your life will
Speaker 1: you breed, how many offspring do you make each of
Speaker 1: those breeding attempts, and how much do you care for them?
Speaker 1: And evolution has happened upon a lot of different answers
Speaker 1: to all of those questions, and it depends on lots
Speaker 1: of stuff like how competitive the environment is, how much
Speaker 1: food is available, how many other individuals are in the population,
Speaker 1: how stable is your environment, et cetera, et cetera. There's
Speaker 1: a lot of different factors that sort of go into
Speaker 1: these decisions, and so the way we think about it
Speaker 1: right now involves a lot more variable and it's quite
Speaker 1: a bit more complicated.
Speaker 3: Yeah, it's complicated.
Speaker 4: It's just like the Facebook message, you know, Like that's
Speaker 4: basically like all these mathematicians, all these evolutionary biologists trying
Speaker 4: to get it down to some nice, beautiful formulas, and
Speaker 4: the best we can come up with is it's complicated.
Speaker 2: In my mind, there's sort of two possible scenarios, or
Speaker 2: maybe a spectrum of them, one in which, like, it's
Speaker 2: complicated and it depends on lots of factors, but if
Speaker 2: you knew all those factors, you could understand it, and
Speaker 2: you know, everybody is responding to those factors in a
Speaker 2: way that makes sense to us. And the other is
Speaker 2: that it's just kind of random, like does everything have
Speaker 2: to have a reason, Like, you know, you might ask
Speaker 2: why are there so many different kind of eye colors
Speaker 2: in humans? Is there a reason why that is? Or
Speaker 2: just sort of like, hey, these are the group that
Speaker 2: survived and a lot of it is just random. How
Speaker 2: much of it does need to be explained. How much
Speaker 2: of it can we just say, hey, this is sort
Speaker 2: of just what happened.
Speaker 1: Yeah, so that's a great question. I mean, I think
Speaker 1: we are, over time having a better understan standing of
Speaker 1: what factors you need to think about ahead of time.
Speaker 1: If you were to predict, like if somebody plopped a
Speaker 1: brand new species in front of you, we could ask
Speaker 1: a certain set of questions and have a pretty good
Speaker 1: guess for what that animal should do. And it depends
Speaker 1: a little bit on like evolutionary trajectory. If it's a mammal,
Speaker 1: then probably female's going to be the one who's doing
Speaker 1: a lot of investing. So you'd predict that the males
Speaker 1: would try to mate with as many females as they
Speaker 1: could to maximize numbers, and then the females are going
Speaker 1: to have to invest a lot more heavily in the
Speaker 1: offscoing that they have, and so it is becoming more
Speaker 1: of a predictive science. But it's taken a lot of work.
Speaker 4: Let's say you, Katie, evolution is really interesting because you
Speaker 4: always have an element of randomness, right, Genetic mutation is random,
Speaker 4: although geologists would disagree, right, an earthquake is quasi random,
Speaker 4: right when it comes to animals, Like an animal certainly
Speaker 4: can't predict when an earthquake happens or some like dramatic
Speaker 4: environmental change happens. You know, sort of like whether or
Speaker 4: not you're just in the right place at the wrong
Speaker 4: time or the wrong place at the right time. All
Speaker 4: of those things are these random things. But when you
Speaker 4: have a system over long, long, long periods of time,
Speaker 4: that's when randomness starts to get shaped into something that
Speaker 4: seems more intentional, seems more like, oh, this feels like
Speaker 4: this is becoming more and more efficient. But the truth
Speaker 4: is that the species that we see today, we are
Speaker 4: just sort of lucky enough to have this glimpse of
Speaker 4: the earth at this period of time where we have
Speaker 4: all these species, and they are not like ideal optimized
Speaker 4: creatures in every sense, right, Like a lot of the
Speaker 4: evolutionary traits that they have, like some of them have
Speaker 4: been selected for, and some of them have been either
Speaker 4: initially selected for and then evolution switched up on them, right,
Speaker 4: like where their environment switched up and the strategy has
Speaker 4: to switch. But they never got rid of it, right
Speaker 4: because it either wasn't harming them or they just never
Speaker 4: lucked into the gene that helped them get rid of it. Right,
Speaker 4: So evolution doesn't create perfectly optimized, streamlined animals, but it
Speaker 4: does create animals that, generally speaking, are good at survival.
Speaker 4: And so there's like some potential randomness right where it's like,
Speaker 4: just happened to be.
Speaker 3: That this basically worked.
Speaker 4: It's like an old car that's like, yeah, it's got
Speaker 4: pretty bad mileage and the carburetor makes a weird noise,
Speaker 4: but it's still going. And there are species like that
Speaker 4: where it's like it's not perfect, but it's still going.
Speaker 3: Some of it can be a little bit random and
Speaker 3: certainly not perfect.
Speaker 1: Yes, I feel not perfectly suited to my environment much
Speaker 1: of the time. And on that note, Daniel, did you
Speaker 1: want to ask an alien related question? Or are you good?
Speaker 2: Oh my gosh, The answer to that is always yes.
Speaker 1: All right, we can pull back. Do you want to
Speaker 1: ask your alien question?
Speaker 3: Green is the answer, green, Miakati?
Speaker 2: My question is what color are alien nipples?
Speaker 3: You know what?
Speaker 4: I've always imagined them as lavender, not funny.
Speaker 2: Maybe they also taste like lavender.
Speaker 4: Yuh hey, you know what, We're getting into some real
Speaker 4: strange territory here.
Speaker 2: Right.
Speaker 3: Thanks for being on the show, Katie, Yeah, absolutely, thanks
Speaker 3: for having me.
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