Speaker 1: What are the greatest mysteries in science? Surely up near
Speaker 1: the top of the list have to be questions like
Speaker 1: how did the universe begin? Or how will it all end?
Speaker 1: Or how can anyone understand organic chemistry? These are all
Speaker 1: amazing questions, and I'd love to know the answers to
Speaker 1: any of them. But in my opinion, the biggest mysteries
Speaker 1: are the most personal ones, the questions we have about
Speaker 1: why we are here, how we came to be, who
Speaker 1: we are. The answers to those questions are the context
Speaker 1: of our existence, and they can't help but shape the
Speaker 1: way we live and guide our future. So that's why
Speaker 1: the history of humanity's evolution has always been so fascinating
Speaker 1: to me, because it's our story. Where did humanity originate?
Speaker 1: How did we spread around the globe? What catastrophes did
Speaker 1: we barely survive? And what marks did that leave in
Speaker 1: our genetic heritage? Why are we so smart or why
Speaker 1: aren't we much smarter? What happened to all of our
Speaker 1: hominid cousins? And what was it like to live on
Speaker 1: an earth with several closely related, interbreeding, intelligent communities. We
Speaker 1: don't have the answers to all of those questions, but
Speaker 1: modern techniques are beginning to flesh out some of the
Speaker 1: biggest blank spots we have in our history and to
Speaker 1: help us grapple with the other side of that question,
Speaker 1: what does the future hold? Is humanity fixed or still changing?
Speaker 1: Has evolution had it to day or are we still
Speaker 1: evolving today? On the podcast, we'll chat with doctor Scott
Speaker 1: Solomon about all of that, and of course about aliens.
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Evolving Universe.
Speaker 2: Hi.
Speaker 1: I'm Daniel. I'm a particle physicist, but I love biology
Speaker 1: and biologists, well maybe one or two in particular.
Speaker 3: I'm Kelly Wader Smith, parasitologist. And you are singing a
Speaker 3: different tune than you did the other day, Daniel, because
Speaker 3: the other day you told me you weren't a huge
Speaker 3: fan of biology. So I'm glad to see you're coming around.
Speaker 1: Well, it may be that my biologist's wife heard that
Speaker 1: episode and so we had a conversation.
Speaker 3: Good good. I'm glad. My cartoonist husband the other day
Speaker 3: when I told him that there was a physics topic
Speaker 3: I wasn't super excited about. He was like, you are
Speaker 3: exhibiting a distinct lack of curiosity. I was like, all right, fine,
Speaker 3: So anyway, our partners are keeping us in line.
Speaker 1: I love the wealth of topics that anybody can dive
Speaker 1: into because there's so many things to be curious about
Speaker 1: in this universe. And that's why we call it the
Speaker 1: podcast the Extraordinary Universe, right, because it's filled with amazing
Speaker 1: things to learn about, from our own particular history to
Speaker 1: whether antelopes do string theory.
Speaker 3: Yeah, I totally agree. One of the things that stresses
Speaker 3: me out about having a shortened lifespan is that I
Speaker 3: will never get to know about all the topics that
Speaker 3: I want to know about. There's so many cool things
Speaker 3: I could be learning about, but I don't have time
Speaker 3: to read about all of them. But on the show
Speaker 3: get through a lot of them.
Speaker 1: So that's my question for you. Actually, So in an
Speaker 1: alternative universe where you got to pick a different kind
Speaker 1: of science to do instead of being a parasitologist, you
Speaker 1: would have been.
Speaker 3: A oh my gosh, that is really hard. I think
Speaker 3: there's a world where I could have really enjoyed being
Speaker 3: a historian or being someone who like spent all day
Speaker 3: digging in the dirt. Although, as we'll hear later in
Speaker 3: the episode that requires a degree of patience that I
Speaker 3: might not have realized when I was excited about those
Speaker 3: ideas when I was younger.
Speaker 1: But that makes sense to me because you always do
Speaker 1: a deep dive in the research of asking you a question.
Speaker 1: You're like, I read three books about this and ten
Speaker 1: pages of notes, so I'm like, WHOA.
Speaker 3: Well, I really like to feel confident before I open
Speaker 3: my mouth, so I'm quiet a lot of times when
Speaker 3: I don't feel confident. But I don't know, just any
Speaker 3: job that involves a lot of time reading and trying
Speaker 3: to understand something deeply. I think there's lots of things
Speaker 3: I could have done with my life that I really
Speaker 3: would have enjoyed, but I only have this one lifetime.
Speaker 3: What about you?
Speaker 1: Ooh, that's a good question.
Speaker 3: It's your question, Daniel. You don't get to say that's
Speaker 3: a great question when it's your question.
Speaker 1: It's a way for me to delay giving an answer because.
Speaker 3: I have one, got it.
Speaker 1: You know, everybody else in my family is a computer
Speaker 1: scientist of some sort, and I actually have a degree
Speaker 1: in computer science, and so I couldn't decide between physics
Speaker 1: and computer science, and I took both paths until basically
Speaker 1: I applied to grad school in both areas, and then
Speaker 1: I had to make a decision. So I chose physics
Speaker 1: because I wanted to be a tool user instead of
Speaker 1: a tool builder. But I still love building tools for
Speaker 1: other people to use. And so in some other universe,
Speaker 1: I'm a programmer, you know, maybe working on scientific tools,
Speaker 1: maybe something else, who knows. But I love writing programs,
Speaker 1: and so I could have just done that as a
Speaker 1: career rather than having it be like the day to
Speaker 1: day work of my science career.
Speaker 3: That's pretty cool that, like, if you could rewind and
Speaker 3: do a completely different career, the other career you would
Speaker 3: have done is something that you get to do a
Speaker 3: lot of in your day to day life. That suggests
Speaker 3: to me that you have really, like made some good
Speaker 3: choices in your life.
Speaker 1: Yeah. Except if I did the other career, I've probably
Speaker 1: making a lot more money.
Speaker 3: Oh yeah, yeah, Yeah, I also did not pick a
Speaker 3: lucrative career. Most people don't care about what's happening to
Speaker 3: brain infecting parasites on little fishies. But what are you
Speaker 3: gonna do?
Speaker 1: Yeah, but you're right, and I feel lucky that the
Speaker 1: day to day work of my job does connect with
Speaker 1: my other interests, and the people who work for me
Speaker 1: end up going off to make a lot more money
Speaker 1: than I do working for Google or Facebook or whatever.
Speaker 1: So yeah, it worked out pretty well. And I've just
Speaker 1: love that there's so many things to be excited about,
Speaker 1: and so many ways life could go, and so many
Speaker 1: things to be curious about. And I love that our
Speaker 1: listeners seem to share that that really resonates with them,
Speaker 1: because they seem to be curious about all sorts of topics,
Speaker 1: from the details of quantum gravity all the way to
Speaker 1: how are we here and what is the history and
Speaker 1: future of humanity?
Speaker 3: And I have been loving that we've been getting more
Speaker 3: biology questions lately, and today's episode is essentially the answer
Speaker 3: to a wonderful biology question that we got from our
Speaker 3: listener named Seth. So let's go ahead and listen to
Speaker 3: Seth's awesome question before we introduce the guest we brought
Speaker 3: on the show to answer the question.
Speaker 4: Hi, Daniel and Kelly, I have some questions related to
Speaker 4: human evolution. Are we slowly evolving as a species as
Speaker 4: we have in the past. If we are, in what
Speaker 4: ways are we evolving and what is driving that evolution?
Speaker 4: Are there pockets or groups of people evolving at different
Speaker 4: rates where natural selection may still play a large role,
Speaker 4: What changes might arise in humans from future evolution, And finally,
Speaker 4: what might evolution look like in a future society living
Speaker 4: on another planet.
Speaker 1: Thanks love the question. The only complaint I have about
Speaker 1: it is that you don't need to apologize at the
Speaker 1: end for asking questions. We love questions. Send us as
Speaker 1: many as you have, really no limits. Please write to
Speaker 1: us with your questions to questions at Daniel and Kelly
Speaker 1: dot org, not Daniel and Kelly dot com. That's the
Speaker 1: wedding website for a very nice looking couple.
Speaker 3: That's right. That's right. So it turns out I have
Speaker 3: a really good friend named Scott Solomon who wrote a
Speaker 3: book on whether or not humans are still evolving, and
Speaker 3: he's just wrapped up his second book about what human
Speaker 3: evolution might look like when humans move out and become interplanetary.
Speaker 3: So today we're going to have Scott on the show
Speaker 3: to answer the first set of questions about human evolution
Speaker 3: here on Earth.
Speaker 1: Yeah yeah, and.
Speaker 3: We'll have him back on the show some other time
Speaker 3: to talk about his next book and the questions about
Speaker 3: the future of human evolution. When that book becomes available.
Speaker 1: Future ya Future Yay.
Speaker 3: So let's go ahead and bring Scott on the show.
Speaker 3: Scott Solomon is a teaching professor in the Department of
Speaker 3: Biosciences at Rice University. He's the author of Future Humans
Speaker 3: Inside the Science of Our Continuing Evolution, and his upcoming book,
Speaker 3: tentatively entitled Becoming Martian How Living in Space will Change
Speaker 3: Our Bodies and Minds, is coming out through MIT Press
Speaker 3: in late twenty twenty five early twenty twenty six. He
Speaker 3: hosts the podcast Wild World with Scott Solomon, taught What
Speaker 3: Darwin Didn't know the Modern science of Evolution for the
Speaker 3: Great Courses, and you can check out his streaming series
Speaker 3: Becoming Martian on Curiosity stream. And that's like a small
Speaker 3: subset of many things that my good friend Scott Solomon does.
Speaker 3: He's incredible. We had to just take a couple so anyway,
Speaker 3: welcome to the show.
Speaker 2: Scott, Hey, Kelly, Hey Daniel.
Speaker 1: Can you also leap buildings in a single bound?
Speaker 5: I wish, Oh my gosh, maybe I'll evolve to be
Speaker 5: able to in the future.
Speaker 3: Right there, we can hit an interesting misconception. Do humans evolve, Scott,
Speaker 3: or is it populations and species that.
Speaker 5: Evol Well, humans as a species can evolve, but yeah,
Speaker 5: individual people, like any individual organism, can maybe change a
Speaker 5: little bit. We like to think we can improve ourselves
Speaker 5: over time, but we wouldn't call that evolution.
Speaker 1: Even if you're bitten by a radioactive spider.
Speaker 5: Well, that's a change I keep hoping for. But I'm
Speaker 5: going for radioactive ant ideally, but still not evolution unless
Speaker 5: your kids also inherit those extraordinary abilities.
Speaker 3: Yep, all right, I mean you go lots of dangerous places.
Speaker 3: Is that kind of like the goal that some radioactive
Speaker 3: animal will get.
Speaker 5: You searching everywhere for the radioactive ant to bite me?
Speaker 2: Yeah, I'm still looking.
Speaker 5: I was just an Antarctica, and contrary to what you
Speaker 5: might imagine, there are no ants in Antarctica.
Speaker 2: So well, at least not that we found.
Speaker 3: Yeah, you know, there are no Kelly Wienersmith's in Antarctica either,
Speaker 3: because it is way too cold. But you jumped into
Speaker 3: the water in Antarctica.
Speaker 2: I did. It was crazy, Yes.
Speaker 3: I would describe it as crazy.
Speaker 1: I would describe that as poor judgment.
Speaker 5: Well, there was a diver in a dry suit perched
Speaker 5: on the edge of the platform you dive from, prepared
Speaker 5: to basically drag your lifeless body out of the water.
Speaker 5: So I felt like they had all the contingencies covered.
Speaker 3: All right, But you've already had your kids, and so
Speaker 3: in terms of evolution, you've like checked that box. Good move.
Speaker 3: So you've mentioned that you are super into ants already.
Speaker 3: So as a person whose PhD was in ant work
Speaker 3: and evolutionary questions, what got you interested in studying human
Speaker 3: evolution in particular?
Speaker 5: Yeah, so I've been interested in human evolution for a
Speaker 5: very long time. Actually, I took a class as a
Speaker 5: college student in anthropology. I first really was introduced to
Speaker 5: human evolution and what we do and don't know about it,
Speaker 5: and I was just absolutely fascinated and actually considered going
Speaker 5: into the field of paleoanthropology, which is the field where
Speaker 5: people are studying human evolution.
Speaker 2: But I ended up going a different route.
Speaker 5: I was actually pre med at the time and thought
Speaker 5: I was going to be a doctor, mainly because I
Speaker 5: didn't know that there were a lot of other options
Speaker 5: for people who like biology and want to have a career,
Speaker 5: and so I did the pre med thing.
Speaker 1: You were like, doctor, or I can work at a zoo.
Speaker 1: Those are the options.
Speaker 2: Yeah, right, Well, yeah, exactly.
Speaker 5: Yeah, Yeah, it's just I didn't have role models in
Speaker 5: my life of people who were doing other kinds of
Speaker 5: biology careers.
Speaker 1: I guess were your parents' academics or not.
Speaker 5: Yeah, so my dad was a professor, but an accounting professor,
Speaker 5: so quite different. I thought I was going in a
Speaker 5: very different direction by going into biology, and then it
Speaker 5: turns out that I ended up having an academic career
Speaker 5: very much like his in some ways so different.
Speaker 1: After all, you're both wrangkling spreadsheets and email. But he's
Speaker 1: probably not jumping into the water in Antarctica.
Speaker 2: That's true. That's true.
Speaker 1: Yeah, counting is a little safer as a profession indeed.
Speaker 2: Indeed, yes, yes, but.
Speaker 1: What you say really resonates with me thinking about anthropology.
Speaker 1: I remember hearing about that field and thinking like, wow,
Speaker 1: this is it. I mean, all of science is some
Speaker 1: kind of attempt to understand the universe and our context
Speaker 1: of our lives, but like anthropology is literally like what
Speaker 1: is the history? How did we get here? Why are
Speaker 1: we here? In terms of like why are we who
Speaker 1: we are? So absolutely I think that's it's like, yea
Speaker 1: one of the most fascinating questions in science.
Speaker 5: No, exactly, I mean, I've always been fascinated by these
Speaker 5: big idea questions like who are we, where do we
Speaker 5: come from?
Speaker 2: And where are we headed? Right, And that's what the
Speaker 2: stuff is all about.
Speaker 5: So yeah, I took a few twists and turns in
Speaker 5: my career, and as you mentioned, Kelly, I ended up
Speaker 5: for my PhD research studying ants, which seems like it
Speaker 5: has nothing to do with human evolution, except that ants
Speaker 5: in some ways are sort of similar to human right,
Speaker 5: they have like complex societies. And the answer that I
Speaker 5: was studying leafcutter ants they grow their own food, they
Speaker 5: have agriculture, and they manage disease outbreaks, and they do
Speaker 5: all these sort of complicated things that we normally associate
Speaker 5: with people. And so, in a sort of strange way,
Speaker 5: studying ants helped me eventually to get back to thinking
Speaker 5: about people, because I knew that ants never stopped evolving, right,
Speaker 5: It's very clear from our studies of ants that they
Speaker 5: have evolved and are evolving and expect them to continue evolving.
Speaker 5: So why not people? And that got me to think
Speaker 5: as a young faculty member. It actually the question came
Speaker 5: to me as actually a question I asked my students.
Speaker 5: I was teaching a class, an introductory biology class, and
Speaker 5: we were learning about evolution, and I just said to
Speaker 5: the students, well, do you think humans are still evolving?
Speaker 5: And you know, that was a question that clearly struck
Speaker 5: a chord with my class. They had a lot of
Speaker 5: thoughts about that. They had their own questions. It was like,
Speaker 5: you know, if you're a professor, right, you guys know,
Speaker 5: like you get your students talking, that's right, that's what
Speaker 5: you want to do. And so I was like, oh,
Speaker 5: this is an interesting topic. I wonder what we really
Speaker 5: know about it. And that led me down this path
Speaker 5: of eventually researching and writing a whole book on the
Speaker 5: topic of whether humans are still evolving and if so.
Speaker 1: How how hard is it to make that kind of
Speaker 1: transition professionally? I mean, if you were like known in
Speaker 1: the ant world and you published on ants and you
Speaker 1: can get ant grants, is it then hard to be
Speaker 1: taken seriously in another field? I mean, I know, in physics,
Speaker 1: for example, we're so niche that like, if you do
Speaker 1: collider physics and then you write a grant proposal on
Speaker 1: you know, cosmic ray physics, They're like, who is this guy?
Speaker 1: He knows nothing? Yeah? Right, does it to make that
Speaker 1: kind of leap.
Speaker 2: Yeah, I mean I think it's interesting.
Speaker 5: I guess the challenge for me was that if you
Speaker 5: look at a lot of popular science, often it's either
Speaker 5: written by somebody who was writing about their own field, right,
Speaker 5: and we're used to that, or somebody who isn't necessarily
Speaker 5: a scientist themselves, but they're writing about a particular topic
Speaker 5: that they've researched. And I was trying to do something
Speaker 5: that was sort of in between those two, right, and Kelly,
Speaker 5: I mean you've done, you know, very similar things in
Speaker 5: your career as well, right, where you sort of have
Speaker 5: a certain amount of expertise that you can apply to
Speaker 5: the thing that you're researching and writing about, but you're still,
Speaker 5: at the end of the day an outsider in this
Speaker 5: very particular field that you're researching and writing about. So
Speaker 5: I found the transition to be, for myself kind of straightforward,
Speaker 5: because you know, we are used to talking to one
Speaker 5: another about research that is not exactly what we work on.
Speaker 5: I mean, we all have conversations with our colleagues and
Speaker 5: go to meetings and it's just sort of like that.
Speaker 5: But you have to kind of encourage people to answer
Speaker 5: questions in a way that is a little different from
Speaker 5: how you would speak to you know, your peers, which
Speaker 5: of course you guys know very well because it's what
Speaker 5: you do here on the podcast. It's a lot of fun,
Speaker 5: it is, it is.
Speaker 1: It's one of my favorite side benefits of doing the
Speaker 1: podcast is we'll be working on an episode about, you know,
Speaker 1: how galaxies formed, and I'm like, well, I never took
Speaker 1: a class on that. Let me go learn about it. It's
Speaker 1: like an excuse to learn something about it and go
Speaker 1: talk to the experts and digest it. Yeah, it's a
Speaker 1: lot of fun.
Speaker 2: Yeah.
Speaker 3: The other day, I was embarrassed to realize that I
Speaker 3: didn't know why the Y chromosome is smaller than the
Speaker 3: X chromosome, and I was like, oh, I need to
Speaker 3: explain that on a show. So I guess I'm spending
Speaker 3: four hours reading about that and it ended up being great.
Speaker 3: And also my insecurities are slowly going away something. Oh
Speaker 3: I didn't know that, but now I know that anyway.
Speaker 5: Well, and I think partly like I'm sure you've both experiences.
Speaker 5: In teaching, university classes were often asked to teach something
Speaker 5: that is a little outside or a lot outside of
Speaker 5: our own research areas, and so, yeah, we have to
Speaker 5: learn as much as we can about it so that
Speaker 5: we can explain it to students and keep.
Speaker 2: Ahead of them. Yeah, so we do that, right.
Speaker 5: I think it's just a slightly different way. I mean, Daniel,
Speaker 5: you've done this too, right, So, like, I find it
Speaker 5: to be kind of a natural thing to do. I
Speaker 5: think maybe it looks weird from the outside to certain people.
Speaker 2: I don't know.
Speaker 5: I don't know if it does, but I really enjoy it.
Speaker 5: Like you said, it's fun to explore topics that are
Speaker 5: not the things that we know are always reading about
Speaker 5: and doing and talking about on a daily basis.
Speaker 3: Yeah, so let's back up and let's get into the
Speaker 3: meat of the content of the book. So let's just
Speaker 3: start with like a simple definition of like what is
Speaker 3: evolution and how do you go about measuring evolution and
Speaker 3: like showing that it's happening.
Speaker 5: Yeah, So biologists define evolution as change over generations, and
Speaker 5: I guess specifically we these days define evolution and measure
Speaker 5: it by talking about evolution as change in allele frequencies
Speaker 5: over generation. So an allele is just a version of
Speaker 5: a gene. So to give a like overly simplistic. Example,
Speaker 5: you can have a gene for hair color, and the
Speaker 5: different alleles would be like an allele for brown hair,
Speaker 5: an allele for black hair, and allele for blonde hair,
Speaker 5: for red hair, et cetera. So how common each of
Speaker 5: those alleles is in a population. If that changes over time,
Speaker 5: if they either become more common or less common, then
Speaker 5: we say evolution has happened. And so that's something that
Speaker 5: is very quantifiable. It's something we can go out and
Speaker 5: look for in a population and say, look, this allele
Speaker 5: has become more common, it's become less common. The next question,
Speaker 5: of course is why. But just whether or not evolution
Speaker 5: has taken place is really just as simple as is
Speaker 5: this allele or the trait that it codes for changing
Speaker 5: in how common it is?
Speaker 1: Isn't there always change happening just due to randomness? I mean,
Speaker 1: if you measured like the fraction of the population that
Speaker 1: had brown hair, even if there wasn't large scale change happening,
Speaker 1: it'd be going up and down. This noise in that measurement, right,
Speaker 1: is there like a threshold beyond But you say, okay,
Speaker 1: this is meaningful change and this is statistical noise.
Speaker 5: Yeah, so we actually have an equation that we can
Speaker 5: use to measure whether there has been significant change from
Speaker 5: one generation to the next. It's called the Hardy Weinberg
Speaker 5: equilibrium equation, and we can measure it. The key thing
Speaker 5: here is that it has certain assumptions, and the assumptions
Speaker 5: actually are sort of the thing that man makes it
Speaker 5: most interesting, I would say, because as you point out,
Speaker 5: we actually almost never find that a population is not evolving,
Speaker 5: is not changing in allele frequencies. So the only ways
Speaker 5: that it would not be changing where if a set
Speaker 5: of five very strict assumptions are in fact taking place.
Speaker 5: And those assumptions are that everybody has equal chances of survival,
Speaker 5: not just chances, equal actual outcomes of survival. There's completely
Speaker 5: random mating, So who's mating with whom? It's all completely random.
Speaker 1: That sounds like an interesting society.
Speaker 5: Yes, exactly right, right, Well, it gets even more implausible
Speaker 5: an infinite population size or a near infinite population size.
Speaker 5: Good luck with that, no movement. Nobody's allowed to move around.
Speaker 5: Everybody has to stay in the same geographical location.
Speaker 1: Then how a You're going to mate with a random
Speaker 1: person in this infinite society If you can't exactly exactly right,
Speaker 1: exactly even assign a mate in China. Oops, well I
Speaker 1: can't go there.
Speaker 2: So.
Speaker 5: You've got it exactly right. And then the last one
Speaker 5: is no mutation, so no genetic changes can pop up spontaneously.
Speaker 5: And of course the point here is that we know
Speaker 5: that all of those are constantly taking place in any
Speaker 5: real population, whether it's humans or any other species. So
Speaker 5: because of that, we expect that there's always going to
Speaker 5: be evolution taking place, and that is in fact what
Speaker 5: we see.
Speaker 1: I think there's also a sometimes disconnect between the public
Speaker 1: conception of a topic and the scientific use of the words.
Speaker 1: So when you say evolution, you just defined it very crisply,
Speaker 1: But when the public here is evolution, I think they
Speaker 1: mean big changes over a long time, Like, you know,
Speaker 1: we used to have common ancestors with apes and chimpanzees
Speaker 1: and everything on earth, And so can you help us
Speaker 1: disentangle like the difference between macro evolution and micro evolution?
Speaker 1: And you know, I often see on social media creationists
Speaker 1: are admitting like, Okay, micro evolution happens, but macro evolution
Speaker 1: is nonsense. Yeah, is there an important scientific distinction there?
Speaker 5: Yeah, exactly, So we have this kind of historical distinction
Speaker 5: that we've made between micro and macro evolution, And basically
Speaker 5: the difference between them is that microevolution is any change
Speaker 5: that is happening within a species, and it's all the
Speaker 5: things that we were just talking about, mutations, violation of
Speaker 5: random mating, or individuals moving around that we can get
Speaker 5: into all of those types of things. Macro evolution is
Speaker 5: evolutionary changes at the species level or above. And so
Speaker 5: the question then becomes, can we explain macro evolution through
Speaker 5: the processes that we understand very well of micro evolution,
Speaker 5: And I think there's still ongoing work in doing that,
Speaker 5: but I think the short answer is yes, we can. Right,
Speaker 5: we can look at how new species come into existence,
Speaker 5: and we can point to the microevolutionary processes that are
Speaker 5: giving rise to the evolution of a new species. And
Speaker 5: then once you've got different species, then of course there
Speaker 5: are sort of other processes that can take place over
Speaker 5: long periods of time that can lead to those sort
Speaker 5: of large scale patterns that we see, like you know,
Speaker 5: increases in body size and like dinosaurs and things like that.
Speaker 5: Those are macroevolutionary trends. But at the end of the day,
Speaker 5: we can boil everything down to those microevolutionary processes that
Speaker 5: are operating within a particular species.
Speaker 3: On the topic of popular misconceptions about evolution, I think
Speaker 3: that when people in the general public talk about evolution,
Speaker 3: they also sort of imply a value judgment, like, when
Speaker 3: evolution is happening that always results in improvement? Is that true?
Speaker 5: It is not true, And I agree with you, Kelly,
Speaker 5: I think that is a common misconception. Yeah, I mean
Speaker 5: we have this notion of progress, right, that like, every
Speaker 5: time evolution is happening, it's making a species better. And
Speaker 5: basically the way that we would typically talk about this
Speaker 5: in you know, evolutionary biology is natural selection.
Speaker 2: Is one of the mechanisms of microevolution.
Speaker 5: Natural selection, of course, this is what Darwin figured out, right,
Speaker 5: and that is the process that makes a specie better
Speaker 5: adapted to its environment. So in that sense you can
Speaker 5: see it as a kind of progress perhaps, But the
Speaker 5: other mechanisms of evolution that can change allele frequencies, they
Speaker 5: do not necessarily. In fact, they do not we would
Speaker 5: not expect them to make a species better adapted to
Speaker 5: its environment. So just getting like, you know, Daniel, you're
Speaker 5: saying about like what about just random changes and an
Speaker 5: allele becoming more or less common. Absolutely, that can happen,
Speaker 5: And of course you wouldn't expect that randomness to make
Speaker 5: a species better at living in its environment. So those
Speaker 5: changes do not lead to what we sort of might
Speaker 5: look at and call progress or improvement.
Speaker 1: And it's not hard to think of an example of
Speaker 1: a random natural selection. Say, for example, there's a supernova
Speaker 1: that sends in incredible amount of radiation towards our solar
Speaker 1: system and kills everybody on one half of the planet
Speaker 1: instantly and the other half are protected by the Earth.
Speaker 1: Doesn't make the people who survived better or even better
Speaker 1: adapted at living, right, They're just like flip a coin.
Speaker 2: They have to survive, yeah exactly.
Speaker 1: It sort of puzzles me sometimes that people think that
Speaker 1: things that survive are always better, or the things that
Speaker 1: propagate into the future always better. Like every time I
Speaker 1: get an upgrade on my iPhone, I'm like, man, this sucks,
Speaker 1: you know, it's a pretty common experience. Or I'd be like, man,
Speaker 1: the good old days were better.
Speaker 2: Yeah. Change is not always good.
Speaker 5: Exactly right, It can just be changed, yeah, yeah exactly.
Speaker 2: Yeah.
Speaker 5: Yeah, we have a name for this process, right, So
Speaker 5: in biology, the process of this kind of random fluctuation
Speaker 5: in allele frequencies we call genetic drift. So the idea
Speaker 5: is that the frequency of an allele is just drifting
Speaker 5: up or drifting down over time, and it's hard to
Speaker 5: predict because it's random. Right, If something is getting more common,
Speaker 5: it's not because it's better in some way, it's just
Speaker 5: because of random change. And we actually see that operating
Speaker 5: all the time in species, especially in small populations, where
Speaker 5: it can be a pretty powerful agent of change.
Speaker 3: All right, so I think we should dig into that
Speaker 3: topic a little bit more, and when we get back,
Speaker 3: Scott Solomon is going to tell us about whether or
Speaker 3: not we can see genetic drift happening in humans. And
Speaker 3: we're back. So Scott Solomon was telling us about genetic drift,
Speaker 3: which is sort of random changes in a little frequencies
Speaker 3: over time. And so, Scott, is this our first example
Speaker 3: of evolution happening in humans? Do we see this happening
Speaker 3: in our species?
Speaker 2: Yeah?
Speaker 5: So, actually, there are some interesting examples of genetic drift
Speaker 5: operating in humans. And one of the I think really
Speaker 5: interesting examples is from an island in the Pacific, the
Speaker 5: island of pingalap It's called pingalap Atoll, and this is
Speaker 5: out in the western Pacific, and in seventeen seventy five
Speaker 5: there was a major typhoon that struck this island and
Speaker 5: it was very catastrophic. Out of about one thousand people
Speaker 5: that were living on this island, there were only twenty survivors,
Speaker 5: so it was a devastating disaster for the people living there.
Speaker 5: And it turned out that one of the twenty survivors
Speaker 5: was the ruler. And this ruler happened to be a
Speaker 5: carrier for a genetic condition known as a chromatopsia better
Speaker 5: known as complete color blindness wow, and he himself was
Speaker 5: not colorblind. He was a carrier, meaning that this is
Speaker 5: a recessive allele, and you have to have two copies
Speaker 5: of the recessive allele to actually have the condition of
Speaker 5: complete color blindness. But because there were only twenty survivors,
Speaker 5: what that meant is that after a few generations, that
Speaker 5: rare recessive allele had actually become much more common in
Speaker 5: the population. And after about four generations you started seeing
Speaker 5: the first individuals that had two copies of that rare allele,
Speaker 5: and they in fact were colorblind, completely COLORBLINDO and So
Speaker 5: if you go to that population today, it's something like
Speaker 5: one in every ten people are color blind. And if
Speaker 5: you compare that with the sort of frequency of that
Speaker 5: condition in humans in general, it's normally more like one
Speaker 5: in thirty thousand people. So you have this rare condition
Speaker 5: that just happened to become more common due to chance,
Speaker 5: due to genetic drift operating once that population became very small,
Speaker 5: and as it recovered, it just happened to get more
Speaker 5: common over time, and now it's surprisingly common.
Speaker 1: And just to close off a potential avenue of criticism there,
Speaker 1: It's not like the reason this guy survived is said
Speaker 1: he had this gene. It's not like it made him
Speaker 1: exactly that right. Well, those twenty people survived out of
Speaker 1: the thousand, was it just totally random?
Speaker 5: I don't think we do know, although I would hazard
Speaker 5: a guess that it probably wasn't random that the ruler survived.
Speaker 2: I'm guessing the ruler.
Speaker 5: May have had access to things that not everybody else
Speaker 5: had access to that might have made it more likely
Speaker 5: for him to survive. But in terms of the other nineteen,
Speaker 5: I don't know if there was any particular reason why
Speaker 5: they have them to survive.
Speaker 1: So I'm really fascinated to here about current human evolution,
Speaker 1: but I'm also really curious about the history of human evolution.
Speaker 1: How well we know that story. I keep reading articles
Speaker 1: about how we've discovered a new fossil which completely upends
Speaker 1: our story of human evolution. Is that just clickbait? Are
Speaker 1: we constantly learning new things about the story of human evolution?
Speaker 1: Do we have a complete picture? Is the concept of
Speaker 1: a missing link a popular misunderstanding and out of date concept,
Speaker 1: or are there really gaps in the story?
Speaker 2: Yeah?
Speaker 5: So you know this idea of a missing link, which
Speaker 5: I think we hear about all the time, not only
Speaker 5: in the context of human evolution, but an evolution in general.
Speaker 5: That concept goes back to the eighteen hundreds, when the
Speaker 5: idea of evolution was still new, and in fact, there
Speaker 5: were no fossils of early humans. So Darwin speculates that
Speaker 5: eventually somebody would find fossils of an early human or
Speaker 5: some human like species that can kind of make the
Speaker 5: connection between us and what he assumed were our closest
Speaker 5: living relatives, the great apes. And we now know first
Speaker 5: of all that in fact, the great apes, the chimpanzees, gorillas,
Speaker 5: and orangutans are in fact our closest living relatives. We
Speaker 5: can tell from looking at genetic and genomic data. It's
Speaker 5: quite clear. That's not disputed at all anymore. And we
Speaker 5: know in fact, specifically that chimpanzees are our closest living relatives.
Speaker 1: And that doesn't mean that we are descended from chimpanzees,
Speaker 1: but that we and chimpanzees have a common ancestor.
Speaker 5: Yes, that's exactly right. So what it means is that
Speaker 5: about six to seven million years ago, there was a
Speaker 5: species that was not a chimpanzee and was not a human,
Speaker 5: and there was a split, and one lineage eventually gave
Speaker 5: rise to the chimpanzees, and the other lineage eventually gave
Speaker 5: rise to humans. So this concept of a link was
Speaker 5: you know, it made sense back in the mid eighteen
Speaker 5: hundreds when there weren't any fossils that kind of span
Speaker 5: that time period, but that is definitely not the case today.
Speaker 5: So we have had an incredible last you know, one
Speaker 5: hundred hundred and fifty years in the fields of paleo anthropology,
Speaker 5: archaeology and paleontology, and the number of specimens that has
Speaker 5: come into our collections or scientific understanding is just remarkable. So, yes,
Speaker 5: there are still questions, there are still gaps, there are
Speaker 5: still a lot of things that we don't fully understand,
Speaker 5: but the picture of human evolution in the past is
Speaker 5: much clearer than it used to be. And so one
Speaker 5: of the things I think that's really clear, Like, one
Speaker 5: of the big take home messages from the study of
Speaker 5: human evolution in the past is that this old idea
Speaker 5: of what's called the march of progress. If you like
Speaker 5: just close your eyes and picture human evolution, right, you
Speaker 5: very likely have this image in your mind of like
Speaker 5: a hunch to over ape looking thing that kind of
Speaker 5: is moving from left to right and standing up a
Speaker 5: little bit straighter and eventually upright. And then you know,
Speaker 5: if this is like a funny meme, then it might
Speaker 5: kind of go from there to like being hunched over
Speaker 5: a computer.
Speaker 2: Or something like that.
Speaker 5: But the idea of this march of progress is that
Speaker 5: you know, there was a linear progression from something that
Speaker 5: was more like an ape to us, and we now
Speaker 5: know that that notion is really not correct. In fact,
Speaker 5: there was not a linear progression one you know, A
Speaker 5: leading to B leading to C leading to D, but
Speaker 5: instead there was really this incredible explosion of diversity that
Speaker 5: took place, meaning that at any one point in time,
Speaker 5: there were multiple species of humans or human like species
Speaker 5: we call these hominids alive at any one point in time,
Speaker 5: and that always blows my mind. It's actually only very
Speaker 5: very recently that we live in a world where there's
Speaker 5: only one type of human.
Speaker 1: How disappointing. Wouldn't it be awesome to have like six
Speaker 1: or seven different kinds of humans that the politics have
Speaker 1: probably be insane.
Speaker 5: For sure, for sure, yeah, exactly, but intriguing, right like
Speaker 5: how do they interact and they view one another?
Speaker 2: And this is what a lot of people are trying
Speaker 2: to work on today.
Speaker 5: But yeah, we definitely have way more information about the
Speaker 5: history of human evolution, how we became human, than we've
Speaker 5: ever had in the past. But as you point out,
Speaker 5: there are new discoveries still being made that kind of
Speaker 5: shake up that understanding, and part of that involves discovery
Speaker 5: of new species. So these keep happening. People are out
Speaker 5: there finding these incredible things. So in South Africa, and
Speaker 5: I think it was in twenty thirteen, there was the
Speaker 5: discovery in a cave of a species called Homo nouletti.
Speaker 5: And this is just remarkable, a lot of unanswered questions
Speaker 5: about it, but you know that species hadn't been seen previously.
Speaker 5: And then in twenty nineteen, Homo lousenensis was discovered in
Speaker 5: the Philippines. So you know, we keep finding new species
Speaker 5: that contribute to a sort of a clearer picture of
Speaker 5: our evolution. They still kind of, you know, give us
Speaker 5: some new mysteries to solve, but they also help to
Speaker 5: kind of fill in some of those gaps.
Speaker 1: It's so amazing, but also to me so frustrating to
Speaker 1: think that there are fossils out there waiting to be undearthed.
Speaker 1: They're just lying in a cave that could reveal so
Speaker 1: much about our story, and like we just don't know
Speaker 1: where they are. If somebody could just like say over
Speaker 1: here and over there, and these fossils by the way,
Speaker 1: because they're just sitting there waiting. It's like in physics
Speaker 1: if somebody had done a bunch of experiments that revealed
Speaker 1: the nature of the universe and then just like hidden
Speaker 1: them around the Globe's.
Speaker 5: Yes, it's absolutely true, and the people that are doing
Speaker 5: this work are incredibly patient people. I have to say,
Speaker 5: so I co teach a class at Rice University in
Speaker 5: the summer where I co teach this with my colleague
Speaker 5: Manuel Dominguez Rodrigo, who is himself a paleo anthropologist and
Speaker 5: an archaeologist, and he works at old and VII Gorge
Speaker 5: and Tanzania, and we brought students out there and one
Speaker 5: of the things that the students got to do is
Speaker 5: help with the excavations that his team is doing at
Speaker 5: these sites that are, you know, like one and a
Speaker 5: half million years old.
Speaker 2: And one of the.
Speaker 5: Things that I took away from that is, you know,
Speaker 5: you can see the excavations that they're doing, and you
Speaker 5: can understand what they're unearthing, but you look at the
Speaker 5: hill that they're kind of digging into, and as you
Speaker 5: point out, Daniel, there's so much more in there. They
Speaker 5: know there's more in there. They don't know exactly what,
Speaker 5: but they know there's more in there. But it takes
Speaker 5: them years and sometimes more than years, like decades, to
Speaker 5: very slowly and very carefully chip away at that hillside,
Speaker 5: at that slope, because they want to very very meticulously
Speaker 5: not only unearth it, but be able to describe the
Speaker 5: exact spatial relationships between each of the things that they're finding.
Speaker 5: Because they get so much information from that, so they're
Speaker 5: very very careful people and you know, very patient people.
Speaker 5: I would struggle with that.
Speaker 1: It's incredible who we found anything, you know, it takes
Speaker 1: so much time, so much luck. I have these fantasies
Speaker 1: about like developing scanning technology that you could just like
Speaker 1: see everything inside the earth and automatically just like identify
Speaker 1: this stuff. Man, maybe someday there'll be a transformational leap
Speaker 1: in our technology.
Speaker 2: Oh, that'd be great.
Speaker 3: In Jurassic Park.
Speaker 2: There you go, exactly if only.
Speaker 3: We could recreate all the stuff in Jurassic part that would.
Speaker 2: Be what could possibly Yeah.
Speaker 3: That's right, that's right, no doubt.
Speaker 1: But that's definitely not a cautionary tale. No, no, no,
Speaker 1: no no.
Speaker 3: I think when most people read the title of today's episode,
Speaker 3: are humans still evolving? They were expecting that they would
Speaker 3: hear a story about how we're getting better at dealing
Speaker 3: with some stressor are there examples like that as well,
Speaker 3: where we can show that humans are evolving in response
Speaker 3: to something that's bad and we're doing better now because
Speaker 3: of that.
Speaker 1: Yeah, tell us some good news.
Speaker 5: Scott Well, I think one of the clear examples of
Speaker 5: ways in which evolution is still happening for humans today
Speaker 5: has to do with disease, right, So we know that
Speaker 5: disease has been a major player in our species history.
Speaker 5: We can look at malaria as an example of a
Speaker 5: disease that we know has a very long history in humans,
Speaker 5: and unfortunately, because it has a tendency to not only
Speaker 5: kill people, but to kill people when they're very young,
Speaker 5: it has had a major effect on human evolution because
Speaker 5: any individual that happens to have a slight ability to
Speaker 5: kind of tolerate malaria, or might be able to survive
Speaker 5: a little bit longer with malaria, or even to really
Speaker 5: kind of fight it off completely, those individuals are likely
Speaker 5: to survive longer and are more likely to pass on
Speaker 5: their genes to children who are going to inherit those abilities.
Speaker 5: And so we see examples of traits that are related
Speaker 5: to resistance to malaria popping up in different human populations
Speaker 5: in areas where malaria was common. So examples of this
Speaker 5: include sickle cell disease. So sickle cell disease we think
Speaker 5: of it as a disease, and it very much is
Speaker 5: for people living today, especially in areas where there isn't malaria,
Speaker 5: But it just so happens that if you have one
Speaker 5: copy of the allele for sickle cell disease, you have
Speaker 5: a certain amount of resistance to severe malaria. And because
Speaker 5: of that, that allele was favored by natural selection for many,
Speaker 5: many years in parts of the world that have a
Speaker 5: lot of malaria. Thalacemia is another example of that, particularly
Speaker 5: in the Mediterranean region. Different types of thalocemia like betas
Speaker 5: thalacemia is a condition that can help you to survive
Speaker 5: a malarial infection. So that was the case in the past.
Speaker 5: It's much less the case today because of course, we
Speaker 5: have access to other types of prevention and treatment for malaria. Actually,
Speaker 5: there are still some places in the world where there
Speaker 5: isn't sufficient access to modern medicine, and there's some indication
Speaker 5: that natural selection actually still does favor those conditions in
Speaker 5: those parts of the world. That have been some studies
Speaker 5: that have documented that. But we can also point to
Speaker 5: more recent disease outbreaks, right, and so for example, COVID nineteen. Actually,
Speaker 5: there's some studies that suggest that there are genetic traits
Speaker 5: that are correlated with people having a more severe reaction
Speaker 5: to COVID nineteen, and that suggests that that is a
Speaker 5: trait that is at least capable of evolving, meaning that
Speaker 5: the genetic condition that would make somebody sort of better
Speaker 5: able to handle COVID nineteen without having a severe reaction
Speaker 5: to it could become more common over time. And you know,
Speaker 5: while nobody wishes for there to be more pandemics, it
Speaker 5: is unfortunately likely that new diseases will continue to pop
Speaker 5: up in the future, and you know, we should expect
Speaker 5: that any individuals that have a little bit of an
Speaker 5: advantage when it comes to tolerating those diseases are going
Speaker 5: to be more likely to pass those traits on to
Speaker 5: their children.
Speaker 3: Yeah, this is, of course. The thing that sucks about
Speaker 3: natural selection is it requires people to die for it to.
Speaker 5: Happen, exactly right. Yeah, it is not a pleasant process.
Speaker 5: It's not a good process in the sense, but it
Speaker 5: does work.
Speaker 3: When I talk to people about are human still evolving?
Speaker 3: The question that I usually get asked is like, well,
Speaker 3: we've got all of these antibiotics, we've got all of
Speaker 3: these ways of keeping people alive, So evolution is probably
Speaker 3: not happening anymore because all of these things that used
Speaker 3: to kill us we can protect ourselves from now. And
Speaker 3: I feel like, what you're saying is to some extent
Speaker 3: that's true, but we don't have that great stuff everywhere,
Speaker 3: and there's still some new stuff that pops up from
Speaker 3: time to time to kill us. So, yeah, how do
Speaker 3: you respond to that critique?
Speaker 5: Yeah, so you're absolutely right that natural selection is not
Speaker 5: operating in the same way as it has in the past,
Speaker 5: because we have all sorts of things, not only modern medicine,
Speaker 5: but other types of technologies that can help us to
Speaker 5: deal with all of these things. And that means that
Speaker 5: we're not just stuck with whatever sort of the genetic
Speaker 5: cards that you were dealt at birth, right, Like, it's
Speaker 5: not only about those traits that we inherit from our parents.
Speaker 5: They do play a role, and so there is still
Speaker 5: the possibility for natural selection to operate, and the data
Speaker 5: suggests that natural selection is operating, but I think increasingly
Speaker 5: we have this kind of separation where other factors our culture,
Speaker 5: our society, our behaviors, our collective intelligence can play some
Speaker 5: of the role that natural selection used to play.
Speaker 1: The way I think about it is natural selection still happens,
Speaker 1: of course, It's just that the environment we're adapted to
Speaker 1: is being changed and manipulated. We're modifying what's required to survive,
Speaker 1: which means natural selection selects for different things. Right in
Speaker 1: this case, you know, the wealth of your parents is
Speaker 1: probably a factor because of the healthcare they can provide
Speaker 1: in all sorts of stuff.
Speaker 2: Yeah, for sure.
Speaker 5: No, that's definitely operating today in a way that probably
Speaker 5: was the case in the past. But of course those
Speaker 5: differences in wealth are so exaggerated today in a way
Speaker 5: that they wouldn't have been if you look back at
Speaker 5: early humans.
Speaker 3: And this is why biologists don't get invited to a
Speaker 3: lot of parties. We're going to take a break and
Speaker 3: when we get back, we're going to ask Scott about
Speaker 3: whether or not our MicroB iome is evolving with us.
Speaker 1: All Right, we're back, and Kelly's joking about how biologists
Speaker 1: don't get invited to parties. But as a physicist, I
Speaker 1: knew that the best thing to do to make a
Speaker 1: physics party fund was to invite a bunch of biologists.
Speaker 2: Yeah.
Speaker 3: Well, that's because every party's better with and that's what
Speaker 3: we bring to the table.
Speaker 1: And it also improved the gender balance.
Speaker 3: All right, Scott, So microbiomes, right, We've got a lot
Speaker 3: of interest in microbiomes these days. Do they play averle
Speaker 3: in our evolution or do we impact how they evolve?
Speaker 3: Is their cross play there? What's going on with our microbiomes.
Speaker 5: I'm fascinated by the microbiome. I mean, I feel like
Speaker 5: this is one of the areas in biology in the
Speaker 5: last just couple of decades that's totally changed the way
Speaker 5: that we think about the world, nature, ourselves. So I
Speaker 5: think part of the answer is it's still such a
Speaker 5: new field that we're still trying to sort of, you know,
Speaker 5: wrap our heads around it and fully understand it. But
Speaker 5: we do know a few things. So one of the
Speaker 5: things that is known is that, first of all, many
Speaker 5: of the microbes that live in and on our bodies,
Speaker 5: what we call the microbiome, they do things that are helpful,
Speaker 5: are useful, right, And we also know that there are
Speaker 5: certain types of microbes that only live in our bodies,
Speaker 5: like you don't find that same species of microbe in
Speaker 5: other species, even in our closest relatives. And in fact,
Speaker 5: if you look at the evolutionary history of some of
Speaker 5: those species and trace it not only in our own lineage,
Speaker 5: but also in our closest living relatives like chimps and
Speaker 5: gorillas and orangutans. The relationships among the microbes mirror the
Speaker 5: relationships among the apes, and what that tells us is
Speaker 5: that as we evolved, they evolved to they've been co
Speaker 5: evolving together with us. And so combining that with the
Speaker 5: knowledge that many of these microbes are helpful does sort
Speaker 5: of lead us to think that, yeah, you know, these
Speaker 5: species may have influenced our evolution, we may have influenced
Speaker 5: their evolution.
Speaker 2: It's probably a little of both.
Speaker 1: How do you learn about the history of evolution of microbes?
Speaker 1: Is it just looking at the genetic codes and how
Speaker 1: much variation there is.
Speaker 5: Yeah, it is looking at the genetics. So basically we
Speaker 5: need to get samples of the microbes, and this is
Speaker 5: often done looking at gut microbes. We've got microbes all
Speaker 5: over us, but the greatest number in diversity is in
Speaker 5: our digestive tract, in our stomach and our especially our intestines.
Speaker 2: So you need to get access to like.
Speaker 5: A gorilla's gut microbiome, and that is not something that
Speaker 5: you know people are normally siting up to know volunteer
Speaker 5: to do.
Speaker 1: Aren't chimpanzees constantly throwing their poop at people? It seems
Speaker 1: like could be pretty easier.
Speaker 5: Yeah, just a butterfly net. Wait, make it angry and
Speaker 5: then catch what comes at you. That's yeah, let's write
Speaker 5: a proposal. Luckily, it turns out that yeah, actually poop
Speaker 5: is the answer. So yes, see, it all comes back
Speaker 5: to the poop, right, Kelly, I knew.
Speaker 3: We'd get there. I knew it.
Speaker 2: Yeah.
Speaker 5: Yeah, So it turns out the microbes that are in
Speaker 5: poop are a pretty good representation of the microbes that
Speaker 5: are in the intestines more generally. And so what you
Speaker 5: need to do is go out and like find gorilla poop.
Speaker 5: And so, you know, researchers will do things like, for example,
Speaker 5: to train dogs to sniff out gorilla poop, and then
Speaker 5: you know, you can go around the forest and look
Speaker 5: for gorilla poop, take some samples and sequence.
Speaker 1: The DNA science is always glamorous, isn't it. It's just
Speaker 1: always glamorous. It's like James Bond every day.
Speaker 3: Imagine being trained for that job.
Speaker 2: The poop sniffing dog.
Speaker 5: Yeah, this is like the dogs that didn't make it
Speaker 5: to the like drug sniffing school.
Speaker 2: Or something like that.
Speaker 3: But you know, I bet the real challenge there is
Speaker 3: getting the poop away from the dog before it rolls
Speaker 3: in it.
Speaker 2: Yeah, that's true. My dogs would not be good at that.
Speaker 1: I bet that dog is very proud of the roles
Speaker 1: playing in our scientific understanding, as he should.
Speaker 2: They should be they should be.
Speaker 1: Yes, yeah, exactly, this boy of science. Yes, good job.
Speaker 3: Our listener also had a question about are humans affecting
Speaker 3: the evolution of other species on the planet more than
Speaker 3: we have in the past. What do you think about that?
Speaker 2: We definitely are.
Speaker 5: I mean, look, first of all, there's just more of
Speaker 5: us than there ever have been by you know, orders
Speaker 5: of magnitude, so of course you would expect us to
Speaker 5: have a bigger impact. And of course we also have
Speaker 5: much more technology than we've ever had in the past,
Speaker 5: and that means that our ability to affect the rest.
Speaker 2: Of the world is enhanced.
Speaker 5: So yeah, I mean there's tons of examples, right, Some
Speaker 5: of them, actually, I would say, are reminiscent of the
Speaker 5: impacts that we've had in the past, like, for example,
Speaker 5: through hunting. So there's actually an interesting study of elephants
Speaker 5: in Mozambique that showed that they are evolving to become tuskless.
Speaker 5: And the reason is very sad. It's because, of course,
Speaker 5: the elephants are being killed for the ivory that their
Speaker 5: tusks are made out of. But what it means is
Speaker 5: that any elephant that happens to be born without tusks
Speaker 5: has a real survival advantage. And there is a genetic
Speaker 5: trait in some of these elephants in which some of
Speaker 5: the females it's only females. Unfortunately for the males, they
Speaker 5: can be born without tusks. And so there was a
Speaker 5: study that showed that because of how much poaching was
Speaker 5: taking place in Mozambique, particularly during the civil war that
Speaker 5: took place there, that actually the rise in tusklessness was
Speaker 5: like threefold. So in other words, it used to be
Speaker 5: pretty rare for an elephant to be born tuskless, and
Speaker 5: now it's something like about half of the females are
Speaker 5: born without tusks. So that is clearly humans have having
Speaker 5: a major impact on this particular population. And I say
Speaker 5: that's like the things that you know. I mean, humans
Speaker 5: have been hunting elephants since before we were Homo sapiens, right,
Speaker 5: So in that sense, it's not new. It's just that
Speaker 5: we're so good at it now that the elephants don't
Speaker 5: stand a chance. Unfortunately, but yeah, we're having other impacts, right,
Speaker 5: I mean, climate change of course is a huge one,
Speaker 5: and we see examples of coral evolving to be able
Speaker 5: to tolerate warmer sea temperatures. Right, The question is can
Speaker 5: they evolve fast enough? And can all of them evolve
Speaker 5: that ability or only some of them?
Speaker 1: Right, Because evolution is not omnipotent, Right, It's possible to
Speaker 1: just wipe out a species if there isn't enough diversity
Speaker 1: and just zero it out, and then it just can't recover.
Speaker 2: Right exactly.
Speaker 5: And you know, evolution only is dealing with whatever is
Speaker 5: the immediate challenge to it. It can't sort of predict
Speaker 5: what's coming down the line. So that stuff is concerning.
Speaker 5: But we do see a lot of examples of humans
Speaker 5: having this impact. I mean, one of the other clear
Speaker 5: examples through our agricultural practices and use of pesticide, so
Speaker 5: we can see the evolution of pesticide resistant insects, or
Speaker 5: in medicine, the evolution of antibiotic resistant bacteria another microorganism.
Speaker 5: So this is clearly an impact that humans are having
Speaker 5: on the natural world that is a much bigger impact
Speaker 5: than what we've ever been able to have before, and
Speaker 5: it is very clearly an evolutionary impact.
Speaker 1: The comment you just made reminds me of a question
Speaker 1: I've long had, which is, basically, why are humans so smart?
Speaker 1: I mean, we evolved in a situation where we needed
Speaker 1: to learn to stay dry and feed ourselves and make friends,
Speaker 1: but not necessarily to play chess and think about eleven
Speaker 1: dimensional spatial manifolds and do super complicated mathematics. Why are
Speaker 1: humans so smart? Do we understand that from an evolutionary
Speaker 1: point of view? What happened in our ancient past to
Speaker 1: create this brain which, as far as I understands, equivalent
Speaker 1: to the brain people had fifty thousand years ago. Why
Speaker 1: did we end up so intelligent?
Speaker 2: Yeah?
Speaker 5: So, I mean, this is actually a really interesting question,
Speaker 5: and it's one of the things that paleo anthropologists are
Speaker 5: trying to study in terms of looking at what we
Speaker 5: can see from the fossil evidence. And one thing that
Speaker 5: is clear is that there was a big expansion in
Speaker 5: the size of the cranium, the part of the skull
Speaker 5: that holds the brain, that happens during the Pleistocene era.
Speaker 5: So this is a period that going back about million
Speaker 5: and a half to you know, two or three million
Speaker 5: years ago, in which there were dramatic climatic changes, dramatic
Speaker 5: climate changes that were happening around the world, and specifically
Speaker 5: changes that were happening in Africa, where our ancestors were
Speaker 5: living at the time. And actually the reason there were
Speaker 5: such dramatic climatic changes has to do with changes in
Speaker 5: the tilt of the Earth. Right, So we are on
Speaker 5: a planet that has a tilt of about twenty three
Speaker 5: and a half degrees at the moment, but that tilt
Speaker 5: changes over time and there's sort of fluctuations. And also
Speaker 5: in the shape of our planet's orbit around the Sun,
Speaker 5: it can be sort of more round or more stretched out.
Speaker 5: And as you sort of put those two changes together,
Speaker 5: you get time periods in which the climate is especially volatile,
Speaker 5: in which you can have relatively rapid swings from really
Speaker 5: wet to really dry, really cold to really warm. And
Speaker 5: that type of change was happening worldwide, but especially in
Speaker 5: Africa during this time period. And that is the time
Speaker 5: in which we see this really dramatic rise in the
Speaker 5: size of the cranium in different species of humans. So
Speaker 5: we think that this was basically natural selection favoring greater intelligence. Now,
Speaker 5: the correlation between brain size and intelligence isn't perfect, right,
Speaker 5: Just because the grain grows larger doesn't necessarily mean that
Speaker 5: they get smarter. I mean, the largest brain of any
Speaker 5: animal species in the world is that of you know,
Speaker 5: certain species of whales, which are they intelligent? Yeah, they're
Speaker 5: pretty intelligent. Are they more intelligent than us? Probably not?
Speaker 5: But in general, we do think that that increase in
Speaker 5: brain size probably had to do with an increase in
Speaker 5: intelligence to a certain extent. So it probably did have
Speaker 5: to do with the ability to handle and cope with
Speaker 5: those dramatic changes. I mean, if you're sort of living
Speaker 5: out on the African savannah and just trying to feed
Speaker 5: your children and not get eaten by lions, you know,
Speaker 5: and you've sort of figured that out to a certain extent,
Speaker 5: and then all of a sudden the climate completely changes, Right,
Speaker 5: you have to figure out a new way to do
Speaker 5: those things. That is really going to be a tall order.
Speaker 5: So we think natural selection was really operating at that
Speaker 5: time to help people to deal with those dramatic changes.
Speaker 5: They had to work together, right, So part of what
Speaker 5: we think is driving some of this change in intelligence
Speaker 5: is the ability to communicate with one another, the ability
Speaker 5: to work together to understand what another person is thinking
Speaker 5: and maybe predict what the other person is going to do,
Speaker 5: and as we all know, that's a hard thing to do.
Speaker 5: So that intelligence would have been favored by natural selection
Speaker 5: as our species was just having to cope with these
Speaker 5: new challenges to our survival.
Speaker 1: There has to be something more than that, right, I mean,
Speaker 1: I know that we don't have the whole picture, of course,
Speaker 1: and I don't expect you to have the whole picture.
Speaker 1: But like other species existed at the same times in
Speaker 1: the same environment, and antelopes can't do string theory right
Speaker 1: as far as I know. Maybe they are and they're
Speaker 1: just not sharing the answers with us.
Speaker 3: Maybe string theory is maladaptive.
Speaker 1: Maybe having physicists is bad for humans. Is that what
Speaker 1: you're saying. But my point is, beyond the only ones
Speaker 1: to face that environment, we seem to be the only
Speaker 1: ones to develop this capacity, not just to solve the
Speaker 1: problems of that era, because you didn't have to be
Speaker 1: able to do string theory to survive in those volatile circumstances,
Speaker 1: but to do this crazy intellectual wrestling matches that we
Speaker 1: do today. So it seems like there's got to be
Speaker 1: more of the story, don't you.
Speaker 5: Think, Yeah, well, it is definitely true that, you know,
Speaker 5: not all species became more intelligent during that time, So
Speaker 5: what was it about us?
Speaker 2: Right?
Speaker 5: And I think one of the answers to that seems
Speaker 5: to be that we already had a bit of a
Speaker 5: head start. So if you look at the change in
Speaker 5: brain size over the last like six million years, like
Speaker 5: going back to the time in which we shared a
Speaker 5: common ancestor with chimpanzees, there was already a trend towards
Speaker 5: bigger brain size in some of the early human ancestors,
Speaker 5: but then it really just sort of rapidly increased in
Speaker 5: size during this period from around one to two million
Speaker 5: years ago. So what was happening then, Well, that's when
Speaker 5: you get these climate changes, So it's probably something to
Speaker 5: do with that. Of course, we need a time machine
Speaker 5: to go back and be able to tell for sure.
Speaker 5: But the reason that other species didn't also become more
Speaker 5: intelligent during that time probably has something to do with
Speaker 5: the fact that they didn't have much genetic variation for
Speaker 5: brain size or intelligence. So that's like a really key
Speaker 5: thing to recognize is that natural selection by itself is
Speaker 5: powerless unless there's some kind of variation that already exists,
Speaker 5: that selection can sort of sift through and say, Okay,
Speaker 5: this version is going to do a better job than
Speaker 5: this other version. And do a better job just means
Speaker 5: basically make more babies. At the end of the day, right,
Speaker 5: evolution it's just all about babies and who's making more babies.
Speaker 5: So if there were some individuals that happened to have
Speaker 5: a slightly bigger brain, happened to be more intelligent, and
Speaker 5: if that led to them making more babies, then you
Speaker 5: know that was what became more common.
Speaker 1: I mean some ultimate universe where a population of humans
Speaker 1: found a different strategy for surviving those vault of times
Speaker 1: by being like really good climbers or super fast, then
Speaker 1: we might all be Usain Bolt today for example.
Speaker 5: Yeah, exactly. Yeah, That's it's pretty stochastic at the end
Speaker 5: of the day. And there's a lot of things that
Speaker 5: could have gone differently that would have turned us into
Speaker 5: a very different species or caused us to not exist
Speaker 5: at all.
Speaker 3: I talked a lot today about different misconceptions people have
Speaker 3: about evolution and human evolution. Are there any others that
Speaker 3: you encounter when you talk to people about evolution that
Speaker 3: are worth debunking while you're on the show.
Speaker 5: Yeah, I guess to me, the one that comes up
Speaker 5: most often is this idea that just because a trait
Speaker 5: seems like it would be useful, that we should expect
Speaker 5: it to evolve, like where are my wings? Scott, Yeah,
Speaker 5: exactly right. Or the one that I hear so often
Speaker 5: is like, you know, hey, everybody's playing video games these days.
Speaker 5: Does that mean our thumbs are going to be bigger
Speaker 5: and stronger in the future, because you know'd be better
Speaker 5: at playing video games? And my answer to that is, well,
Speaker 5: do people, first of all, have variation in thumb size
Speaker 5: and strength.
Speaker 2: I don't know.
Speaker 5: Maybe they do, but that would be one thing that
Speaker 5: would have to be true. The other thing is that
Speaker 5: the people with the big, strong thumbs would have to
Speaker 5: have more babies.
Speaker 2: And that's where I have my doubts.
Speaker 3: So I've read both of your books and yeah, that's right.
Speaker 3: I got to read his second book early. And I
Speaker 3: get the sense from reading your books that you really
Speaker 3: enjoy the travel that goes into researching the book. What
Speaker 3: was your favorite research trip that you've taken for a
Speaker 3: book so far?
Speaker 5: Well, first of all, Kelly, I love that you have
Speaker 5: been willing to read my books, including in advance, and
Speaker 5: you've given me some really great feedback and suggestions, So
Speaker 5: thank you for that.
Speaker 1: Kelly is so good at that she is.
Speaker 3: Ah, thanks guys, It's my pleasure. I love getting to
Speaker 3: read early copies of books.
Speaker 5: But you're right, I do like to travel, and so,
Speaker 5: you know, one of the things that I've enjoyed in
Speaker 5: researching that these books that I've written is traveling around
Speaker 5: and you know, meeting people who are doing interesting work.
Speaker 5: And I really enjoy being able to kind of describe
Speaker 5: the work that someone's doing by kind of you know,
Speaker 5: showing people how they do it, and you know, getting
Speaker 5: to know them in their natural environment, so to speak.
Speaker 5: So yeah, I mean I've done some interesting trips for
Speaker 5: this book, Future Humans. I think the trip that was
Speaker 5: maybe the most fun that I got to do was
Speaker 5: to go to Quebec. And there's an island in the
Speaker 5: Saint Laurence River with a French name that I will
Speaker 5: not attempt to pronounce apologies to my high school French teacher,
Speaker 5: but the reason is that this island is a place
Speaker 5: where there has been a very interesting series of research
Speaker 5: studies by a biologist named Emmanuel Milo, and I got
Speaker 5: to go actually to this island with Emmanuel Milo. We
Speaker 5: traveled there together, and what was interesting about it is
Speaker 5: that this island was first settled by French Canadians in
Speaker 5: the seventeen hundreds, and he and some of his colleagues,
Speaker 5: Emmanuel and some of his colleagues were able to basically
Speaker 5: trace the history of the human population on this island
Speaker 5: and show that there has actually been evolutionary change among
Speaker 5: the people living on that island between about eighteen hundred
Speaker 5: and the nineteen sixties. So this is like, you know,
Speaker 5: roughly sort of seven or eight generations of people that
Speaker 5: lived on this island. And because it was an island,
Speaker 5: because it's kind of hard to get to, it was
Speaker 5: relatively isolated from the surrounding communities. And so what they
Speaker 5: showed is that actually the age at which women had
Speaker 5: their first child changed on that island from averaging about
Speaker 5: twenty six years old to about age twenty two over
Speaker 5: that time span, So women started having their first child
Speaker 5: at a younger age during that time period. And what
Speaker 5: was especially interesting about this population is that they had
Speaker 5: a complete genealogical record of the entire population because of
Speaker 5: church records, so everybody pretty much went to the same church,
Speaker 5: and the church keeps track of births, deaths, and marriages,
Speaker 5: and so because of that, they had this whole genealogy
Speaker 5: of this population and they were able to basically rule
Speaker 5: out that this change in the age of first birth
Speaker 5: it could have been due to other factors. You might
Speaker 5: imagine that it was like, well, some people might have been,
Speaker 5: you know, richer or poorer, or had access to more
Speaker 5: food or different culture, whatever it is, right, And basically
Speaker 5: they were able to rule out all of those other
Speaker 5: possibilities and show that in fact, it was a response
Speaker 5: to natural selection. So basically natural selection was favoring women
Speaker 5: starting their families at a younger age because women that do,
Speaker 5: on average tend to have more children, and that is
Speaker 5: actually something that is predicted from evolutionary theory, but it
Speaker 5: had never been shown before in humans, particularly not in
Speaker 5: a modern human population. So it was really interesting. It's
Speaker 5: a beautiful place. They are lovely people. We got to
Speaker 5: go and spend several days on this island and we
Speaker 5: met a lot of great folks there, got to learn
Speaker 5: a little bit more.
Speaker 2: About the history of the island.
Speaker 5: It was really interesting to go with Emmanuel Milo and
Speaker 5: actually see this place that had been you know, this
Speaker 5: subject of this really interesting study he had done.
Speaker 1: It's amazing how important islands are to the history of
Speaker 1: evolution and our study and understanding of it. Right, We're
Speaker 1: lucky we have islands.
Speaker 2: Yeah, it's true.
Speaker 5: I mean partly because they're sort of like these little
Speaker 5: miniature versions of what are normally much more complex systems. So,
Speaker 5: you know, going back to Darwin, right, you know, in
Speaker 5: the Galapagos. I mean, biologists still go to islands because
Speaker 5: they often helped to kind of reveal more complicated phenomena
Speaker 5: in a somewhat simpler way.
Speaker 3: I also feel like if I could go back and
Speaker 3: have a different career being a historian would be really
Speaker 3: cool to just be able to like handle old documents
Speaker 3: and see like old writings I don't know something about
Speaker 3: like really old stuff. Oh yeah, it is really exciting.
Speaker 2: Absolutely.
Speaker 5: I mean one of the things that we did was
Speaker 5: we actually visited the Archdiocese of Quebec and got to
Speaker 5: see the archives where they actually had these original records
Speaker 5: of birth, deaths, and marriages. We had to open up
Speaker 5: those books and see for ourselves, and I get goosebumps
Speaker 5: when I see that kind of thing, right, I mean,
Speaker 5: it's just getting to have that immediate connection with history.
Speaker 2: I think it's super cool.
Speaker 1: That reminds me of the exhibit in the British Museum
Speaker 1: where they have original manuscripts from famous people, so you
Speaker 1: can see like Mozart's scribbles and Beethoven like crossing stuff
Speaker 1: out and really fascinating to think, like that guy actually
Speaker 1: wrote on this piece of paper. I don't know why,
Speaker 1: but it is really powerful, right.
Speaker 2: It is. We actually at Rice.
Speaker 5: In our library collection, we have the collection of work
Speaker 5: from a biologist named Julian Huxley, who is a famous
Speaker 5: biologist in the early twentieth century. His grandfather, Thomas Henry Huxley,
Speaker 5: was one of Darwin's closest friends, and there is a
Speaker 5: copy of the Origin of Species in the library that
Speaker 5: was given by Charles Darwin to Thomas Henry Huxley, and
Speaker 5: it has both Thomas Henry Huxley and Julian Huxley's notes
Speaker 5: in the margin.
Speaker 2: It's just the.
Speaker 5: Coolest thing to see. No, I still get chills thinking
Speaker 5: about it. Yeah, it's so cool.
Speaker 1: Speaking of chills and connecting back to Antarctica. One of
Speaker 1: the things they have in the British Museum is like
Speaker 1: the logbook of one of these journeys to the South Pole,
Speaker 1: and you can see like the last page where the
Speaker 1: guy rights it is very cold, and then that's it.
Speaker 1: That's the end of the law. Oh yeah, oh they
Speaker 1: found him with it.
Speaker 2: Oh that's ominous.
Speaker 3: Is that the Scott expedition?
Speaker 1: Yeah it might have been yea, yeah exactly, but you
Speaker 1: know he was taking data to the end a real scientist,
Speaker 1: you know, keeping records. But now I want to get
Speaker 1: to the inevitable place we always get to on this podcast,
Speaker 1: because everything leads to aliens and wealism, and I want
Speaker 1: to ask you about aliens because I want to know
Speaker 1: if what we've learned here on Earth is particular to
Speaker 1: our experience here where we tend to have islands and
Speaker 1: we have this particular history, or if this is something
Speaker 1: general and universal we've learned about life in the universe.
Speaker 1: So we're landing on an alien planet and we brought
Speaker 1: you along, Scott. Are you expecting to learn that on
Speaker 1: this planet there's natural selection and this evolution or do
Speaker 1: you think that that those are things that just happen
Speaker 1: here on Earth because of our particular set of circumstances.
Speaker 5: Yeah, I love this question because it forces us to ask, like,
Speaker 5: what is life? And do the things that we know
Speaker 5: about life actually apply, you know, universally or only to
Speaker 5: this particular version of life that we know. We actually
Speaker 5: in biology struggle to even to find what life is.
Speaker 5: And there's a lot of things that are sort of
Speaker 5: like gray areas, like, for example, viruses. Right, I don't know, Kelly,
Speaker 5: if you have opinions on our viruses alive, that's like
Speaker 5: a way to start a fight at a biology conference, right.
Speaker 5: But one of the definitions that people have proposed for
Speaker 5: what is life is that life is capable of evolving,
Speaker 5: and so like by definition, then if we see life,
Speaker 5: then yes, it should be capable of evolving. But that's
Speaker 5: like a circular definition, so it's not very satisfying. So
Speaker 5: I think another way of thinking about it is unless
Speaker 5: another form of life is immortal, if it has immortality
Speaker 5: and one individual can just live forever, then no, they
Speaker 5: wouldn't evolve the way that we think about it. But
Speaker 5: as long as there is mortality, as long as there
Speaker 5: is death, and as long as there is reproduction, and
Speaker 5: as long as there is some way for individuals to
Speaker 5: pass something of themselves to their offspring to the next generation.
Speaker 5: In that basic setup, you will always expect natural selection
Speaker 5: to work. You would always expect the basic principles that
Speaker 5: we've been talking about of evolution to work, and that,
Speaker 5: to me is one of the most powerful things about
Speaker 5: it that I think people don't often realize. We're not
Speaker 5: just saying evolution can happen, or you know, under some
Speaker 5: circumstances you might get changed. No, it's actually inevitable. It's
Speaker 5: sort of built into the system that anytime you have
Speaker 5: a thing that lives for some amount of time, reproduces,
Speaker 5: passes something on somehow to the next generation, right, that
Speaker 5: there will be changes that are heritable that are happening
Speaker 5: from one generation to the next. Now, the specific things
Speaker 5: that are evolving, the traits, the rules that maybe govern
Speaker 5: who survives and how they reproduce, that's all up for graps.
Speaker 1: The biochemical mechanism, whether it's DNA or.
Speaker 5: Not, yeah, exactly, doesn't have to be DNA, doesn't have
Speaker 5: to be anything like the way genetics works for Earth life.
Speaker 5: But as long as there is some mechanism of inheritance
Speaker 5: and as long as there is reproduction and multiple generations,
Speaker 5: there will be evolution.
Speaker 1: I like that you're very clear about the assumptions that
Speaker 1: go into that conclusion, because that immediately opens doors for
Speaker 1: like potential science fiction stories like I imagine now a
Speaker 1: planet where abiogenesis is very common. It didn't just happen once,
Speaker 1: but it's like constantly happening, and you're always getting like
Speaker 1: new forms of life propping up and they don't reproduce,
Speaker 1: they just die out. I guess in that scenario, you
Speaker 1: wouldn't have evolution, right, you just have like a constant,
Speaker 1: random genesis of weird kinds of life.
Speaker 5: Yeah, And that is an interesting thing that I often
Speaker 5: think about, is how come we only see the evolution
Speaker 5: of the origin of life one single time right here
Speaker 5: on Earth that we know of, or at least only
Speaker 5: one lineage of life has left descendants that we can
Speaker 5: find today. Why doesn't it keep happening? And I think
Speaker 5: there's reasons for that that we think we understand, But yeah,
Speaker 5: it could be that in some other world that it
Speaker 5: is much more common for life to just pop up spontaneously.
Speaker 5: And yeah, and that circumstance each individual origin of life
Speaker 5: could give rise to separate sort of evolutionary trajectories. But
Speaker 5: we would still expect them to evolve if they could reproduce.
Speaker 1: Eventually they would end up with podcasts, right.
Speaker 3: Everyone podca can hope that's right. Everyone on the show
Speaker 3: today has.
Speaker 1: Their own podcast, therefore dot that's.
Speaker 3: Right, all right, Well, Scott, this has been amazing and
Speaker 3: informative and a ton of fun. And thank you so
Speaker 3: much for being on the show. And we plan on
Speaker 3: having you back to talk about the future of human evolution,
Speaker 3: which is the second half of the question that we
Speaker 3: got from the listener, what would happen when our species
Speaker 3: moves out into space? So we look forward to having
Speaker 3: you back when you are ready to talk about your
Speaker 3: next book.
Speaker 5: Well, thanks so much, Kelly and Daniel. This has been
Speaker 5: fun and I can't wait to come back.
Speaker 1: Thanks for evolving our understanding of biology.
Speaker 2: Oh anytime.
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