Are Humans Still Evolving? (Featuring Scott Solomon)

Daniel and Kelly chat with Dr. Scott Solomon about how we measure evolution, and whether or not humans are still evolving. 

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Episode Transcript

Speaker 1 (00:04):
What are the greatest mysteries in science? Surely up near
the top of the list have to be questions like
how did the universe begin? Or how will it all end?
Or how can anyone understand organic chemistry? These are all
amazing questions, and I'd love to know the answers to
any of them. But in my opinion, the biggest mysteries
are the most personal ones, the questions we have about

(00:27):
why we are here, how we came to be, who
we are. The answers to those questions are the context
of our existence, and they can't help but shape the
way we live and guide our future. So that's why
the history of humanity's evolution has always been so fascinating
to me, because it's our story. Where did humanity originate?

(00:47):
How did we spread around the globe? What catastrophes did
we barely survive? And what marks did that leave in
our genetic heritage? Why are we so smart or why
aren't we much smarter? What happened to all of our
hominid cousins? And what was it like to live on
an earth with several closely related, interbreeding, intelligent communities. We

(01:09):
don't have the answers to all of those questions, but
modern techniques are beginning to flesh out some of the
biggest blank spots we have in our history and to
help us grapple with the other side of that question,
what does the future hold? Is humanity fixed or still changing?
Has evolution had it to day or are we still
evolving today? On the podcast, we'll chat with doctor Scott

(01:30):
Solomon about all of that, and of course about aliens.
Welcome to Daniel and Kelly's Extraordinary Evolving Universe.

Speaker 2 (01:51):
Hi.

Speaker 1 (01:51):
I'm Daniel. I'm a particle physicist, but I love biology
and biologists, well maybe one or two in particular.

Speaker 3 (01:58):
I'm Kelly Wader Smith, parasitologist. And you are singing a
different tune than you did the other day, Daniel, because
the other day you told me you weren't a huge
fan of biology. So I'm glad to see you're coming around.

Speaker 1 (02:08):
Well, it may be that my biologist's wife heard that
episode and so we had a conversation.

Speaker 3 (02:14):
Good good. I'm glad. My cartoonist husband the other day
when I told him that there was a physics topic
I wasn't super excited about. He was like, you are
exhibiting a distinct lack of curiosity. I was like, all right, fine,
So anyway, our partners are keeping us in line.

Speaker 1 (02:32):
I love the wealth of topics that anybody can dive
into because there's so many things to be curious about
in this universe. And that's why we call it the
podcast the Extraordinary Universe, right, because it's filled with amazing
things to learn about, from our own particular history to
whether antelopes do string theory.

Speaker 3 (02:47):
Yeah, I totally agree. One of the things that stresses
me out about having a shortened lifespan is that I
will never get to know about all the topics that
I want to know about. There's so many cool things
I could be learning about, but I don't have time
to read about all of them. But on the show
get through a lot of them.

Speaker 1 (03:01):
So that's my question for you. Actually, So in an
alternative universe where you got to pick a different kind
of science to do instead of being a parasitologist, you
would have been.

Speaker 3 (03:10):
A oh my gosh, that is really hard. I think
there's a world where I could have really enjoyed being
a historian or being someone who like spent all day
digging in the dirt. Although, as we'll hear later in
the episode that requires a degree of patience that I
might not have realized when I was excited about those
ideas when I was younger.

Speaker 1 (03:28):
But that makes sense to me because you always do
a deep dive in the research of asking you a question.
You're like, I read three books about this and ten
pages of notes, so I'm like, WHOA.

Speaker 3 (03:37):
Well, I really like to feel confident before I open
my mouth, so I'm quiet a lot of times when
I don't feel confident. But I don't know, just any
job that involves a lot of time reading and trying
to understand something deeply. I think there's lots of things
I could have done with my life that I really
would have enjoyed, but I only have this one lifetime.
What about you?

Speaker 1 (03:57):
Ooh, that's a good question.

Speaker 3 (03:59):
It's your question, Daniel. You don't get to say that's
a great question when it's your question.

Speaker 1 (04:05):
It's a way for me to delay giving an answer because.

Speaker 3 (04:07):
I have one, got it.

Speaker 1 (04:10):
You know, everybody else in my family is a computer
scientist of some sort, and I actually have a degree
in computer science, and so I couldn't decide between physics
and computer science, and I took both paths until basically
I applied to grad school in both areas, and then
I had to make a decision. So I chose physics
because I wanted to be a tool user instead of
a tool builder. But I still love building tools for

(04:32):
other people to use. And so in some other universe,
I'm a programmer, you know, maybe working on scientific tools,
maybe something else, who knows. But I love writing programs,
and so I could have just done that as a
career rather than having it be like the day to
day work of my science career.

Speaker 3 (04:46):
That's pretty cool that, like, if you could rewind and
do a completely different career, the other career you would
have done is something that you get to do a
lot of in your day to day life. That suggests
to me that you have really, like made some good
choices in your life.

Speaker 1 (04:59):
Yeah. Except if I did the other career, I've probably
making a lot more money.

Speaker 3 (05:02):
Oh yeah, yeah, Yeah, I also did not pick a
lucrative career. Most people don't care about what's happening to
brain infecting parasites on little fishies. But what are you
gonna do?

Speaker 1 (05:11):
Yeah, but you're right, and I feel lucky that the
day to day work of my job does connect with
my other interests, and the people who work for me
end up going off to make a lot more money
than I do working for Google or Facebook or whatever.
So yeah, it worked out pretty well. And I've just
love that there's so many things to be excited about,
and so many ways life could go, and so many
things to be curious about. And I love that our

(05:33):
listeners seem to share that that really resonates with them,
because they seem to be curious about all sorts of topics,
from the details of quantum gravity all the way to
how are we here and what is the history and
future of humanity?

Speaker 3 (05:46):
And I have been loving that we've been getting more
biology questions lately, and today's episode is essentially the answer
to a wonderful biology question that we got from our
listener named Seth. So let's go ahead and listen to
Seth's awesome question before we introduce the guest we brought
on the show to answer the question.

Speaker 4 (06:02):
Hi, Daniel and Kelly, I have some questions related to
human evolution. Are we slowly evolving as a species as
we have in the past. If we are, in what
ways are we evolving and what is driving that evolution?
Are there pockets or groups of people evolving at different
rates where natural selection may still play a large role,
What changes might arise in humans from future evolution, And finally,

(06:25):
what might evolution look like in a future society living
on another planet.

Speaker 1 (06:29):
Thanks love the question. The only complaint I have about
it is that you don't need to apologize at the
end for asking questions. We love questions. Send us as
many as you have, really no limits. Please write to
us with your questions to questions at Daniel and Kelly
dot org, not Daniel and Kelly dot com. That's the
wedding website for a very nice looking couple.

Speaker 3 (06:48):
That's right. That's right. So it turns out I have
a really good friend named Scott Solomon who wrote a
book on whether or not humans are still evolving, and
he's just wrapped up his second book about what human
evolution might look like when humans move out and become interplanetary.
So today we're going to have Scott on the show
to answer the first set of questions about human evolution
here on Earth.

Speaker 1 (07:07):
Yeah yeah, and.

Speaker 3 (07:07):
We'll have him back on the show some other time
to talk about his next book and the questions about
the future of human evolution. When that book becomes available.

Speaker 1 (07:15):
Future ya Future Yay.

Speaker 3 (07:17):
So let's go ahead and bring Scott on the show.
Scott Solomon is a teaching professor in the Department of
Biosciences at Rice University. He's the author of Future Humans
Inside the Science of Our Continuing Evolution, and his upcoming book,
tentatively entitled Becoming Martian How Living in Space will Change

(07:38):
Our Bodies and Minds, is coming out through MIT Press
in late twenty twenty five early twenty twenty six. He
hosts the podcast Wild World with Scott Solomon, taught What
Darwin Didn't know the Modern science of Evolution for the
Great Courses, and you can check out his streaming series
Becoming Martian on Curiosity stream. And that's like a small

(07:59):
subset of many things that my good friend Scott Solomon does.
He's incredible. We had to just take a couple so anyway,
welcome to the show.

Speaker 2 (08:05):
Scott, Hey, Kelly, Hey Daniel.

Speaker 1 (08:07):
Can you also leap buildings in a single bound?

Speaker 5 (08:10):
I wish, Oh my gosh, maybe I'll evolve to be
able to in the future.

Speaker 3 (08:14):
Right there, we can hit an interesting misconception. Do humans evolve, Scott,
or is it populations and species that.

Speaker 5 (08:20):
Evol Well, humans as a species can evolve, but yeah,
individual people, like any individual organism, can maybe change a
little bit. We like to think we can improve ourselves
over time, but we wouldn't call that evolution.

Speaker 1 (08:34):
Even if you're bitten by a radioactive spider.

Speaker 5 (08:37):
Well, that's a change I keep hoping for. But I'm
going for radioactive ant ideally, but still not evolution unless
your kids also inherit those extraordinary abilities.

Speaker 3 (08:46):
Yep, all right, I mean you go lots of dangerous places.
Is that kind of like the goal that some radioactive
animal will get.

Speaker 5 (08:53):
You searching everywhere for the radioactive ant to bite me?

Speaker 2 (08:57):
Yeah, I'm still looking.

Speaker 5 (08:58):
I was just an Antarctica, and contrary to what you
might imagine, there are no ants in Antarctica.

Speaker 2 (09:03):
So well, at least not that we found.

Speaker 3 (09:06):
Yeah, you know, there are no Kelly Wienersmith's in Antarctica either,
because it is way too cold. But you jumped into
the water in Antarctica.

Speaker 2 (09:13):
I did. It was crazy, Yes.

Speaker 3 (09:16):
I would describe it as crazy.

Speaker 1 (09:17):
I would describe that as poor judgment.

Speaker 5 (09:22):
Well, there was a diver in a dry suit perched
on the edge of the platform you dive from, prepared
to basically drag your lifeless body out of the water.
So I felt like they had all the contingencies covered.

Speaker 3 (09:33):
All right, But you've already had your kids, and so
in terms of evolution, you've like checked that box. Good move.
So you've mentioned that you are super into ants already.
So as a person whose PhD was in ant work
and evolutionary questions, what got you interested in studying human
evolution in particular?

Speaker 5 (09:52):
Yeah, so I've been interested in human evolution for a
very long time. Actually, I took a class as a
college student in anthropology. I first really was introduced to
human evolution and what we do and don't know about it,
and I was just absolutely fascinated and actually considered going
into the field of paleoanthropology, which is the field where
people are studying human evolution.

Speaker 2 (10:14):
But I ended up going a different route.

Speaker 5 (10:17):
I was actually pre med at the time and thought
I was going to be a doctor, mainly because I
didn't know that there were a lot of other options
for people who like biology and want to have a career,
and so I did the pre med thing.

Speaker 1 (10:30):
You were like, doctor, or I can work at a zoo.
Those are the options.

Speaker 2 (10:33):
Yeah, right, Well, yeah, exactly.

Speaker 5 (10:35):
Yeah, Yeah, it's just I didn't have role models in
my life of people who were doing other kinds of
biology careers.

Speaker 1 (10:42):
I guess were your parents' academics or not.

Speaker 5 (10:44):
Yeah, so my dad was a professor, but an accounting professor,
so quite different. I thought I was going in a
very different direction by going into biology, and then it
turns out that I ended up having an academic career
very much like his in some ways so different.

Speaker 1 (11:00):
After all, you're both wrangkling spreadsheets and email. But he's
probably not jumping into the water in Antarctica.

Speaker 2 (11:06):
That's true. That's true.

Speaker 1 (11:08):
Yeah, counting is a little safer as a profession indeed.

Speaker 2 (11:11):
Indeed, yes, yes, but.

Speaker 1 (11:13):
What you say really resonates with me thinking about anthropology.
I remember hearing about that field and thinking like, wow,
this is it. I mean, all of science is some
kind of attempt to understand the universe and our context
of our lives, but like anthropology is literally like what
is the history? How did we get here? Why are
we here? In terms of like why are we who
we are? So absolutely I think that's it's like, yea

(11:35):
one of the most fascinating questions in science.

Speaker 5 (11:37):
No, exactly, I mean, I've always been fascinated by these
big idea questions like who are we, where do we
come from?

Speaker 2 (11:43):
And where are we headed? Right, And that's what the
stuff is all about.

Speaker 5 (11:45):
So yeah, I took a few twists and turns in
my career, and as you mentioned, Kelly, I ended up
for my PhD research studying ants, which seems like it
has nothing to do with human evolution, except that ants
in some ways are sort of similar to human right,
they have like complex societies. And the answer that I
was studying leafcutter ants they grow their own food, they

(12:05):
have agriculture, and they manage disease outbreaks, and they do
all these sort of complicated things that we normally associate
with people. And so, in a sort of strange way,
studying ants helped me eventually to get back to thinking
about people, because I knew that ants never stopped evolving, right,
It's very clear from our studies of ants that they

(12:26):
have evolved and are evolving and expect them to continue evolving.
So why not people? And that got me to think
as a young faculty member. It actually the question came
to me as actually a question I asked my students.
I was teaching a class, an introductory biology class, and
we were learning about evolution, and I just said to
the students, well, do you think humans are still evolving?

(12:50):
And you know, that was a question that clearly struck
a chord with my class. They had a lot of
thoughts about that. They had their own questions. It was like,
you know, if you're a professor, right, you guys know,
like you get your students talking, that's right, that's what
you want to do. And so I was like, oh,
this is an interesting topic. I wonder what we really

(13:10):
know about it. And that led me down this path
of eventually researching and writing a whole book on the
topic of whether humans are still evolving and if so.

Speaker 1 (13:19):
How how hard is it to make that kind of
transition professionally? I mean, if you were like known in
the ant world and you published on ants and you
can get ant grants, is it then hard to be
taken seriously in another field? I mean, I know, in physics,
for example, we're so niche that like, if you do
collider physics and then you write a grant proposal on

(13:39):
you know, cosmic ray physics, They're like, who is this guy?
He knows nothing? Yeah? Right, does it to make that
kind of leap.

Speaker 2 (13:46):
Yeah, I mean I think it's interesting.

Speaker 5 (13:48):
I guess the challenge for me was that if you
look at a lot of popular science, often it's either
written by somebody who was writing about their own field, right,
and we're used to that, or somebody who isn't necessarily
a scientist themselves, but they're writing about a particular topic
that they've researched. And I was trying to do something
that was sort of in between those two, right, and Kelly,

(14:09):
I mean you've done, you know, very similar things in
your career as well, right, where you sort of have
a certain amount of expertise that you can apply to
the thing that you're researching and writing about, but you're still,
at the end of the day an outsider in this
very particular field that you're researching and writing about. So
I found the transition to be, for myself kind of straightforward,
because you know, we are used to talking to one

(14:30):
another about research that is not exactly what we work on.
I mean, we all have conversations with our colleagues and
go to meetings and it's just sort of like that.
But you have to kind of encourage people to answer
questions in a way that is a little different from
how you would speak to you know, your peers, which
of course you guys know very well because it's what
you do here on the podcast. It's a lot of fun,

(14:50):
it is, it is.

Speaker 1 (14:52):
It's one of my favorite side benefits of doing the
podcast is we'll be working on an episode about, you know,
how galaxies formed, and I'm like, well, I never took
a class on that. Let me go learn about it. It's
like an excuse to learn something about it and go
talk to the experts and digest it. Yeah, it's a
lot of fun.

Speaker 2 (15:07):
Yeah.

Speaker 3 (15:08):
The other day, I was embarrassed to realize that I
didn't know why the Y chromosome is smaller than the
X chromosome, and I was like, oh, I need to
explain that on a show. So I guess I'm spending
four hours reading about that and it ended up being great.
And also my insecurities are slowly going away something. Oh
I didn't know that, but now I know that anyway.

Speaker 5 (15:25):
Well, and I think partly like I'm sure you've both experiences.
In teaching, university classes were often asked to teach something
that is a little outside or a lot outside of
our own research areas, and so, yeah, we have to
learn as much as we can about it so that
we can explain it to students and keep.

Speaker 2 (15:40):
Ahead of them. Yeah, so we do that, right.

Speaker 5 (15:43):
I think it's just a slightly different way. I mean, Daniel,
you've done this too, right, So, like, I find it
to be kind of a natural thing to do. I
think maybe it looks weird from the outside to certain people.

Speaker 2 (15:51):
I don't know.

Speaker 5 (15:52):
I don't know if it does, but I really enjoy it.
Like you said, it's fun to explore topics that are
not the things that we know are always reading about
and doing and talking about on a daily basis.

Speaker 3 (16:02):
Yeah, so let's back up and let's get into the
meat of the content of the book. So let's just
start with like a simple definition of like what is
evolution and how do you go about measuring evolution and
like showing that it's happening.

Speaker 5 (16:16):
Yeah, So biologists define evolution as change over generations, and
I guess specifically we these days define evolution and measure
it by talking about evolution as change in allele frequencies
over generation. So an allele is just a version of
a gene. So to give a like overly simplistic. Example,

(16:38):
you can have a gene for hair color, and the
different alleles would be like an allele for brown hair,
an allele for black hair, and allele for blonde hair,
for red hair, et cetera. So how common each of
those alleles is in a population. If that changes over time,
if they either become more common or less common, then
we say evolution has happened. And so that's something that

(17:01):
is very quantifiable. It's something we can go out and
look for in a population and say, look, this allele
has become more common, it's become less common. The next question,
of course is why. But just whether or not evolution
has taken place is really just as simple as is
this allele or the trait that it codes for changing

(17:22):
in how common it is?

Speaker 1 (17:23):
Isn't there always change happening just due to randomness? I mean,
if you measured like the fraction of the population that
had brown hair, even if there wasn't large scale change happening,
it'd be going up and down. This noise in that measurement, right,
is there like a threshold beyond But you say, okay,
this is meaningful change and this is statistical noise.

Speaker 5 (17:41):
Yeah, so we actually have an equation that we can
use to measure whether there has been significant change from
one generation to the next. It's called the Hardy Weinberg
equilibrium equation, and we can measure it. The key thing
here is that it has certain assumptions, and the assumptions
actually are sort of the thing that man makes it
most interesting, I would say, because as you point out,

(18:03):
we actually almost never find that a population is not evolving,
is not changing in allele frequencies. So the only ways
that it would not be changing where if a set
of five very strict assumptions are in fact taking place.
And those assumptions are that everybody has equal chances of survival,

(18:25):
not just chances, equal actual outcomes of survival. There's completely
random mating, So who's mating with whom? It's all completely random.

Speaker 1 (18:35):
That sounds like an interesting society.

Speaker 5 (18:37):
Yes, exactly right, right, Well, it gets even more implausible
an infinite population size or a near infinite population size.
Good luck with that, no movement. Nobody's allowed to move around.
Everybody has to stay in the same geographical location.

Speaker 1 (18:51):
Then how a You're going to mate with a random
person in this infinite society If you can't exactly exactly right,
exactly even assign a mate in China. Oops, well I
can't go there.

Speaker 2 (19:01):
So.

Speaker 5 (19:03):
You've got it exactly right. And then the last one
is no mutation, so no genetic changes can pop up spontaneously.
And of course the point here is that we know
that all of those are constantly taking place in any
real population, whether it's humans or any other species. So
because of that, we expect that there's always going to
be evolution taking place, and that is in fact what

(19:25):
we see.

Speaker 1 (19:25):
I think there's also a sometimes disconnect between the public
conception of a topic and the scientific use of the words.
So when you say evolution, you just defined it very crisply,
But when the public here is evolution, I think they
mean big changes over a long time, Like, you know,
we used to have common ancestors with apes and chimpanzees
and everything on earth, And so can you help us

(19:48):
disentangle like the difference between macro evolution and micro evolution?
And you know, I often see on social media creationists
are admitting like, Okay, micro evolution happens, but macro evolution
is nonsense. Yeah, is there an important scientific distinction there?

Speaker 5 (20:03):
Yeah, exactly, So we have this kind of historical distinction
that we've made between micro and macro evolution, And basically
the difference between them is that microevolution is any change
that is happening within a species, and it's all the
things that we were just talking about, mutations, violation of
random mating, or individuals moving around that we can get
into all of those types of things. Macro evolution is

(20:24):
evolutionary changes at the species level or above. And so
the question then becomes, can we explain macro evolution through
the processes that we understand very well of micro evolution,
And I think there's still ongoing work in doing that,
but I think the short answer is yes, we can. Right,
we can look at how new species come into existence,

(20:46):
and we can point to the microevolutionary processes that are
giving rise to the evolution of a new species. And
then once you've got different species, then of course there
are sort of other processes that can take place over
long periods of time that can lead to those sort
of large scale patterns that we see, like you know,
increases in body size and like dinosaurs and things like that.

(21:06):
Those are macroevolutionary trends. But at the end of the day,
we can boil everything down to those microevolutionary processes that
are operating within a particular species.

Speaker 3 (21:17):
On the topic of popular misconceptions about evolution, I think
that when people in the general public talk about evolution,
they also sort of imply a value judgment, like, when
evolution is happening that always results in improvement? Is that true?

Speaker 5 (21:32):
It is not true, And I agree with you, Kelly,
I think that is a common misconception. Yeah, I mean
we have this notion of progress, right, that like, every
time evolution is happening, it's making a species better. And
basically the way that we would typically talk about this
in you know, evolutionary biology is natural selection.

Speaker 2 (21:51):
Is one of the mechanisms of microevolution.

Speaker 5 (21:54):
Natural selection, of course, this is what Darwin figured out, right,
and that is the process that makes a specie better
adapted to its environment. So in that sense you can
see it as a kind of progress perhaps, But the
other mechanisms of evolution that can change allele frequencies, they
do not necessarily. In fact, they do not we would

(22:14):
not expect them to make a species better adapted to
its environment. So just getting like, you know, Daniel, you're
saying about like what about just random changes and an
allele becoming more or less common. Absolutely, that can happen,
And of course you wouldn't expect that randomness to make
a species better at living in its environment. So those
changes do not lead to what we sort of might

(22:34):
look at and call progress or improvement.

Speaker 1 (22:37):
And it's not hard to think of an example of
a random natural selection. Say, for example, there's a supernova
that sends in incredible amount of radiation towards our solar
system and kills everybody on one half of the planet
instantly and the other half are protected by the Earth.
Doesn't make the people who survived better or even better
adapted at living, right, They're just like flip a coin.

Speaker 2 (22:59):
They have to survive, yeah exactly.

Speaker 1 (23:02):
It sort of puzzles me sometimes that people think that
things that survive are always better, or the things that
propagate into the future always better. Like every time I
get an upgrade on my iPhone, I'm like, man, this sucks,
you know, it's a pretty common experience. Or I'd be like, man,
the good old days were better.

Speaker 2 (23:19):
Yeah. Change is not always good.

Speaker 5 (23:21):
Exactly right, It can just be changed, yeah, yeah exactly.

Speaker 2 (23:25):
Yeah.

Speaker 5 (23:26):
Yeah, we have a name for this process, right, So
in biology, the process of this kind of random fluctuation
in allele frequencies we call genetic drift. So the idea
is that the frequency of an allele is just drifting
up or drifting down over time, and it's hard to
predict because it's random. Right, If something is getting more common,
it's not because it's better in some way, it's just

(23:47):
because of random change. And we actually see that operating
all the time in species, especially in small populations, where
it can be a pretty powerful agent of change.

Speaker 3 (23:58):
All right, so I think we should dig into that
topic a little bit more, and when we get back,
Scott Solomon is going to tell us about whether or
not we can see genetic drift happening in humans. And

(24:23):
we're back. So Scott Solomon was telling us about genetic drift,
which is sort of random changes in a little frequencies
over time. And so, Scott, is this our first example
of evolution happening in humans? Do we see this happening
in our species?

Speaker 2 (24:35):
Yeah?

Speaker 5 (24:35):
So, actually, there are some interesting examples of genetic drift
operating in humans. And one of the I think really
interesting examples is from an island in the Pacific, the
island of pingalap It's called pingalap Atoll, and this is
out in the western Pacific, and in seventeen seventy five
there was a major typhoon that struck this island and

(24:58):
it was very catastrophic. Out of about one thousand people
that were living on this island, there were only twenty survivors,
so it was a devastating disaster for the people living there.
And it turned out that one of the twenty survivors
was the ruler. And this ruler happened to be a

(25:19):
carrier for a genetic condition known as a chromatopsia better
known as complete color blindness wow, and he himself was
not colorblind. He was a carrier, meaning that this is
a recessive allele, and you have to have two copies
of the recessive allele to actually have the condition of
complete color blindness. But because there were only twenty survivors,

(25:43):
what that meant is that after a few generations, that
rare recessive allele had actually become much more common in
the population. And after about four generations you started seeing
the first individuals that had two copies of that rare allele,
and they in fact were colorblind, completely COLORBLINDO and So

(26:03):
if you go to that population today, it's something like
one in every ten people are color blind. And if
you compare that with the sort of frequency of that
condition in humans in general, it's normally more like one
in thirty thousand people. So you have this rare condition
that just happened to become more common due to chance,

(26:26):
due to genetic drift operating once that population became very small,
and as it recovered, it just happened to get more
common over time, and now it's surprisingly common.

Speaker 1 (26:38):
And just to close off a potential avenue of criticism there,
It's not like the reason this guy survived is said
he had this gene. It's not like it made him
exactly that right. Well, those twenty people survived out of
the thousand, was it just totally random?

Speaker 5 (26:52):
I don't think we do know, although I would hazard
a guess that it probably wasn't random that the ruler survived.

Speaker 2 (26:58):
I'm guessing the ruler.

Speaker 5 (26:58):
May have had access to things that not everybody else
had access to that might have made it more likely
for him to survive. But in terms of the other nineteen,
I don't know if there was any particular reason why
they have them to survive.

Speaker 1 (27:10):
So I'm really fascinated to here about current human evolution,
but I'm also really curious about the history of human evolution.
How well we know that story. I keep reading articles
about how we've discovered a new fossil which completely upends
our story of human evolution. Is that just clickbait? Are
we constantly learning new things about the story of human evolution?
Do we have a complete picture? Is the concept of

(27:32):
a missing link a popular misunderstanding and out of date concept,
or are there really gaps in the story?

Speaker 2 (27:38):
Yeah?

Speaker 5 (27:39):
So you know this idea of a missing link, which
I think we hear about all the time, not only
in the context of human evolution, but an evolution in general.
That concept goes back to the eighteen hundreds, when the
idea of evolution was still new, and in fact, there
were no fossils of early humans. So Darwin speculates that

(28:00):
eventually somebody would find fossils of an early human or
some human like species that can kind of make the
connection between us and what he assumed were our closest
living relatives, the great apes. And we now know first
of all that in fact, the great apes, the chimpanzees, gorillas,

(28:21):
and orangutans are in fact our closest living relatives. We
can tell from looking at genetic and genomic data. It's
quite clear. That's not disputed at all anymore. And we
know in fact, specifically that chimpanzees are our closest living relatives.

Speaker 1 (28:34):
And that doesn't mean that we are descended from chimpanzees,
but that we and chimpanzees have a common ancestor.

Speaker 5 (28:40):
Yes, that's exactly right. So what it means is that
about six to seven million years ago, there was a
species that was not a chimpanzee and was not a human,
and there was a split, and one lineage eventually gave
rise to the chimpanzees, and the other lineage eventually gave
rise to humans. So this concept of a link was

(29:01):
you know, it made sense back in the mid eighteen
hundreds when there weren't any fossils that kind of span
that time period, but that is definitely not the case today.
So we have had an incredible last you know, one
hundred hundred and fifty years in the fields of paleo anthropology,
archaeology and paleontology, and the number of specimens that has

(29:24):
come into our collections or scientific understanding is just remarkable. So, yes,
there are still questions, there are still gaps, there are
still a lot of things that we don't fully understand,
but the picture of human evolution in the past is
much clearer than it used to be. And so one
of the things I think that's really clear, Like, one

(29:44):
of the big take home messages from the study of
human evolution in the past is that this old idea
of what's called the march of progress. If you like
just close your eyes and picture human evolution, right, you
very likely have this image in your mind of like
a hunch to over ape looking thing that kind of
is moving from left to right and standing up a

(30:05):
little bit straighter and eventually upright. And then you know,
if this is like a funny meme, then it might
kind of go from there to like being hunched over
a computer.

Speaker 2 (30:14):
Or something like that.

Speaker 5 (30:15):
But the idea of this march of progress is that
you know, there was a linear progression from something that
was more like an ape to us, and we now
know that that notion is really not correct. In fact,
there was not a linear progression one you know, A
leading to B leading to C leading to D, but

(30:37):
instead there was really this incredible explosion of diversity that
took place, meaning that at any one point in time,
there were multiple species of humans or human like species
we call these hominids alive at any one point in time,
and that always blows my mind. It's actually only very
very recently that we live in a world where there's

(30:57):
only one type of human.

Speaker 1 (30:59):
How disappointing. Wouldn't it be awesome to have like six
or seven different kinds of humans that the politics have
probably be insane.

Speaker 5 (31:07):
For sure, for sure, yeah, exactly, but intriguing, right like
how do they interact and they view one another?

Speaker 2 (31:12):
And this is what a lot of people are trying
to work on today.

Speaker 5 (31:14):
But yeah, we definitely have way more information about the
history of human evolution, how we became human, than we've
ever had in the past. But as you point out,
there are new discoveries still being made that kind of
shake up that understanding, and part of that involves discovery
of new species. So these keep happening. People are out
there finding these incredible things. So in South Africa, and

(31:38):
I think it was in twenty thirteen, there was the
discovery in a cave of a species called Homo nouletti.
And this is just remarkable, a lot of unanswered questions
about it, but you know that species hadn't been seen previously.
And then in twenty nineteen, Homo lousenensis was discovered in
the Philippines. So you know, we keep finding new species

(31:58):
that contribute to a sort of a clearer picture of
our evolution. They still kind of, you know, give us
some new mysteries to solve, but they also help to
kind of fill in some of those gaps.

Speaker 1 (32:10):
It's so amazing, but also to me so frustrating to
think that there are fossils out there waiting to be undearthed.
They're just lying in a cave that could reveal so
much about our story, and like we just don't know
where they are. If somebody could just like say over
here and over there, and these fossils by the way,
because they're just sitting there waiting. It's like in physics
if somebody had done a bunch of experiments that revealed

(32:31):
the nature of the universe and then just like hidden
them around the Globe's.

Speaker 5 (32:36):
Yes, it's absolutely true, and the people that are doing
this work are incredibly patient people. I have to say,
so I co teach a class at Rice University in
the summer where I co teach this with my colleague
Manuel Dominguez Rodrigo, who is himself a paleo anthropologist and
an archaeologist, and he works at old and VII Gorge
and Tanzania, and we brought students out there and one

(32:56):
of the things that the students got to do is
help with the excavations that his team is doing at
these sites that are, you know, like one and a
half million years old.

Speaker 2 (33:05):
And one of the.

Speaker 5 (33:06):
Things that I took away from that is, you know,
you can see the excavations that they're doing, and you
can understand what they're unearthing, but you look at the
hill that they're kind of digging into, and as you
point out, Daniel, there's so much more in there. They
know there's more in there. They don't know exactly what,
but they know there's more in there. But it takes
them years and sometimes more than years, like decades, to

(33:28):
very slowly and very carefully chip away at that hillside,
at that slope, because they want to very very meticulously
not only unearth it, but be able to describe the
exact spatial relationships between each of the things that they're finding.
Because they get so much information from that, so they're
very very careful people and you know, very patient people.

(33:51):
I would struggle with that.

Speaker 1 (33:52):
It's incredible who we found anything, you know, it takes
so much time, so much luck. I have these fantasies
about like developing scanning technology that you could just like
see everything inside the earth and automatically just like identify
this stuff. Man, maybe someday there'll be a transformational leap
in our technology.

Speaker 2 (34:07):
Oh, that'd be great.

Speaker 3 (34:08):
In Jurassic Park.

Speaker 2 (34:08):
There you go, exactly if only.

Speaker 3 (34:11):
We could recreate all the stuff in Jurassic part that would.

Speaker 2 (34:13):
Be what could possibly Yeah.

Speaker 3 (34:15):
That's right, that's right, no doubt.

Speaker 1 (34:17):
But that's definitely not a cautionary tale. No, no, no,
no no.

Speaker 3 (34:21):
I think when most people read the title of today's episode,
are humans still evolving? They were expecting that they would
hear a story about how we're getting better at dealing
with some stressor are there examples like that as well,
where we can show that humans are evolving in response
to something that's bad and we're doing better now because
of that.

Speaker 1 (34:39):
Yeah, tell us some good news.

Speaker 5 (34:40):
Scott Well, I think one of the clear examples of
ways in which evolution is still happening for humans today
has to do with disease, right, So we know that
disease has been a major player in our species history.
We can look at malaria as an example of a
disease that we know has a very long history in humans,
and unfortunately, because it has a tendency to not only

(35:04):
kill people, but to kill people when they're very young,
it has had a major effect on human evolution because
any individual that happens to have a slight ability to
kind of tolerate malaria, or might be able to survive
a little bit longer with malaria, or even to really
kind of fight it off completely, those individuals are likely

(35:27):
to survive longer and are more likely to pass on
their genes to children who are going to inherit those abilities.
And so we see examples of traits that are related
to resistance to malaria popping up in different human populations
in areas where malaria was common. So examples of this
include sickle cell disease. So sickle cell disease we think

(35:50):
of it as a disease, and it very much is
for people living today, especially in areas where there isn't malaria,
But it just so happens that if you have one
copy of the allele for sickle cell disease, you have
a certain amount of resistance to severe malaria. And because
of that, that allele was favored by natural selection for many,

(36:11):
many years in parts of the world that have a
lot of malaria. Thalacemia is another example of that, particularly
in the Mediterranean region. Different types of thalocemia like betas
thalacemia is a condition that can help you to survive
a malarial infection. So that was the case in the past.
It's much less the case today because of course, we

(36:34):
have access to other types of prevention and treatment for malaria. Actually,
there are still some places in the world where there
isn't sufficient access to modern medicine, and there's some indication
that natural selection actually still does favor those conditions in
those parts of the world. That have been some studies
that have documented that. But we can also point to

(36:56):
more recent disease outbreaks, right, and so for example, COVID nineteen. Actually,
there's some studies that suggest that there are genetic traits
that are correlated with people having a more severe reaction
to COVID nineteen, and that suggests that that is a
trait that is at least capable of evolving, meaning that

(37:20):
the genetic condition that would make somebody sort of better
able to handle COVID nineteen without having a severe reaction
to it could become more common over time. And you know,
while nobody wishes for there to be more pandemics, it
is unfortunately likely that new diseases will continue to pop
up in the future, and you know, we should expect

(37:42):
that any individuals that have a little bit of an
advantage when it comes to tolerating those diseases are going
to be more likely to pass those traits on to
their children.

Speaker 3 (37:52):
Yeah, this is, of course. The thing that sucks about
natural selection is it requires people to die for it to.

Speaker 5 (37:56):
Happen, exactly right. Yeah, it is not a pleasant process.
It's not a good process in the sense, but it
does work.

Speaker 3 (38:02):
When I talk to people about are human still evolving?
The question that I usually get asked is like, well,
we've got all of these antibiotics, we've got all of
these ways of keeping people alive, So evolution is probably
not happening anymore because all of these things that used
to kill us we can protect ourselves from now. And
I feel like, what you're saying is to some extent

(38:22):
that's true, but we don't have that great stuff everywhere,
and there's still some new stuff that pops up from
time to time to kill us. So, yeah, how do
you respond to that critique?

Speaker 5 (38:30):
Yeah, so you're absolutely right that natural selection is not
operating in the same way as it has in the past,
because we have all sorts of things, not only modern medicine,
but other types of technologies that can help us to
deal with all of these things. And that means that
we're not just stuck with whatever sort of the genetic
cards that you were dealt at birth, right, Like, it's

(38:50):
not only about those traits that we inherit from our parents.
They do play a role, and so there is still
the possibility for natural selection to operate, and the data
suggests that natural selection is operating, but I think increasingly
we have this kind of separation where other factors our culture,
our society, our behaviors, our collective intelligence can play some

(39:13):
of the role that natural selection used to play.

Speaker 1 (39:15):
The way I think about it is natural selection still happens,
of course, It's just that the environment we're adapted to
is being changed and manipulated. We're modifying what's required to survive,
which means natural selection selects for different things. Right in
this case, you know, the wealth of your parents is
probably a factor because of the healthcare they can provide

(39:36):
in all sorts of stuff.

Speaker 2 (39:37):
Yeah, for sure.

Speaker 5 (39:38):
No, that's definitely operating today in a way that probably
was the case in the past. But of course those
differences in wealth are so exaggerated today in a way
that they wouldn't have been if you look back at
early humans.

Speaker 3 (39:50):
And this is why biologists don't get invited to a
lot of parties. We're going to take a break and
when we get back, we're going to ask Scott about
whether or not our MicroB iome is evolving with us.

Speaker 1 (40:17):
All Right, we're back, and Kelly's joking about how biologists
don't get invited to parties. But as a physicist, I
knew that the best thing to do to make a
physics party fund was to invite a bunch of biologists.

Speaker 2 (40:28):
Yeah.

Speaker 3 (40:31):
Well, that's because every party's better with and that's what
we bring to the table.

Speaker 1 (40:36):
And it also improved the gender balance.

Speaker 3 (40:39):
All right, Scott, So microbiomes, right, We've got a lot
of interest in microbiomes these days. Do they play averle
in our evolution or do we impact how they evolve?
Is their cross play there? What's going on with our microbiomes.

Speaker 5 (40:52):
I'm fascinated by the microbiome. I mean, I feel like
this is one of the areas in biology in the
last just couple of decades that's totally changed the way
that we think about the world, nature, ourselves. So I
think part of the answer is it's still such a
new field that we're still trying to sort of, you know,
wrap our heads around it and fully understand it. But
we do know a few things. So one of the
things that is known is that, first of all, many

(41:15):
of the microbes that live in and on our bodies,
what we call the microbiome, they do things that are helpful,
are useful, right, And we also know that there are
certain types of microbes that only live in our bodies,
like you don't find that same species of microbe in
other species, even in our closest relatives. And in fact,

(41:36):
if you look at the evolutionary history of some of
those species and trace it not only in our own lineage,
but also in our closest living relatives like chimps and
gorillas and orangutans. The relationships among the microbes mirror the
relationships among the apes, and what that tells us is

(41:57):
that as we evolved, they evolved to they've been co
evolving together with us. And so combining that with the
knowledge that many of these microbes are helpful does sort
of lead us to think that, yeah, you know, these
species may have influenced our evolution, we may have influenced
their evolution.

Speaker 2 (42:17):
It's probably a little of both.

Speaker 1 (42:19):
How do you learn about the history of evolution of microbes?
Is it just looking at the genetic codes and how
much variation there is.

Speaker 5 (42:25):
Yeah, it is looking at the genetics. So basically we
need to get samples of the microbes, and this is
often done looking at gut microbes. We've got microbes all
over us, but the greatest number in diversity is in
our digestive tract, in our stomach and our especially our intestines.

Speaker 2 (42:43):
So you need to get access to like.

Speaker 5 (42:46):
A gorilla's gut microbiome, and that is not something that
you know people are normally siting up to know volunteer
to do.

Speaker 1 (42:54):
Aren't chimpanzees constantly throwing their poop at people? It seems
like could be pretty easier.

Speaker 5 (42:59):
Yeah, just a butterfly net. Wait, make it angry and
then catch what comes at you. That's yeah, let's write
a proposal. Luckily, it turns out that yeah, actually poop
is the answer. So yes, see, it all comes back
to the poop, right, Kelly, I knew.

Speaker 3 (43:19):
We'd get there. I knew it.

Speaker 2 (43:20):
Yeah.

Speaker 5 (43:20):
Yeah, So it turns out the microbes that are in
poop are a pretty good representation of the microbes that
are in the intestines more generally. And so what you
need to do is go out and like find gorilla poop.
And so, you know, researchers will do things like, for example,
to train dogs to sniff out gorilla poop, and then
you know, you can go around the forest and look

(43:42):
for gorilla poop, take some samples and sequence.

Speaker 1 (43:45):
The DNA science is always glamorous, isn't it. It's just
always glamorous. It's like James Bond every day.

Speaker 3 (43:53):
Imagine being trained for that job.

Speaker 2 (43:56):
The poop sniffing dog.

Speaker 5 (43:57):
Yeah, this is like the dogs that didn't make it
to the like drug sniffing school.

Speaker 2 (44:01):
Or something like that.

Speaker 3 (44:02):
But you know, I bet the real challenge there is
getting the poop away from the dog before it rolls
in it.

Speaker 2 (44:07):
Yeah, that's true. My dogs would not be good at that.

Speaker 1 (44:09):
I bet that dog is very proud of the roles
playing in our scientific understanding, as he should.

Speaker 2 (44:15):
They should be they should be.

Speaker 1 (44:16):
Yes, yeah, exactly, this boy of science. Yes, good job.

Speaker 3 (44:22):
Our listener also had a question about are humans affecting
the evolution of other species on the planet more than
we have in the past. What do you think about that?

Speaker 2 (44:30):
We definitely are.

Speaker 5 (44:31):
I mean, look, first of all, there's just more of
us than there ever have been by you know, orders
of magnitude, so of course you would expect us to
have a bigger impact. And of course we also have
much more technology than we've ever had in the past,
and that means that our ability to affect the rest.

Speaker 2 (44:46):
Of the world is enhanced.

Speaker 5 (44:48):
So yeah, I mean there's tons of examples, right, Some
of them, actually, I would say, are reminiscent of the
impacts that we've had in the past, like, for example,
through hunting. So there's actually an interesting study of elephants
in Mozambique that showed that they are evolving to become tuskless.
And the reason is very sad. It's because, of course,

(45:11):
the elephants are being killed for the ivory that their
tusks are made out of. But what it means is
that any elephant that happens to be born without tusks
has a real survival advantage. And there is a genetic
trait in some of these elephants in which some of
the females it's only females. Unfortunately for the males, they

(45:32):
can be born without tusks. And so there was a
study that showed that because of how much poaching was
taking place in Mozambique, particularly during the civil war that
took place there, that actually the rise in tusklessness was
like threefold. So in other words, it used to be
pretty rare for an elephant to be born tuskless, and

(45:54):
now it's something like about half of the females are
born without tusks. So that is clearly humans have having
a major impact on this particular population. And I say
that's like the things that you know. I mean, humans
have been hunting elephants since before we were Homo sapiens, right,
So in that sense, it's not new. It's just that
we're so good at it now that the elephants don't

(46:16):
stand a chance. Unfortunately, but yeah, we're having other impacts, right,
I mean, climate change of course is a huge one,
and we see examples of coral evolving to be able
to tolerate warmer sea temperatures. Right, The question is can
they evolve fast enough? And can all of them evolve
that ability or only some of them?

Speaker 1 (46:37):
Right, Because evolution is not omnipotent, Right, It's possible to
just wipe out a species if there isn't enough diversity
and just zero it out, and then it just can't recover.

Speaker 2 (46:46):
Right exactly.

Speaker 5 (46:47):
And you know, evolution only is dealing with whatever is
the immediate challenge to it. It can't sort of predict
what's coming down the line. So that stuff is concerning.
But we do see a lot of examples of humans
having this impact. I mean, one of the other clear
examples through our agricultural practices and use of pesticide, so
we can see the evolution of pesticide resistant insects, or

(47:10):
in medicine, the evolution of antibiotic resistant bacteria another microorganism.
So this is clearly an impact that humans are having
on the natural world that is a much bigger impact
than what we've ever been able to have before, and
it is very clearly an evolutionary impact.

Speaker 1 (47:26):
The comment you just made reminds me of a question
I've long had, which is, basically, why are humans so smart?
I mean, we evolved in a situation where we needed
to learn to stay dry and feed ourselves and make friends,
but not necessarily to play chess and think about eleven
dimensional spatial manifolds and do super complicated mathematics. Why are

(47:49):
humans so smart? Do we understand that from an evolutionary
point of view? What happened in our ancient past to
create this brain which, as far as I understands, equivalent
to the brain people had fifty thousand years ago. Why
did we end up so intelligent?

Speaker 2 (48:03):
Yeah?

Speaker 5 (48:03):
So, I mean, this is actually a really interesting question,
and it's one of the things that paleo anthropologists are
trying to study in terms of looking at what we
can see from the fossil evidence. And one thing that
is clear is that there was a big expansion in
the size of the cranium, the part of the skull
that holds the brain, that happens during the Pleistocene era.

(48:24):
So this is a period that going back about million
and a half to you know, two or three million
years ago, in which there were dramatic climatic changes, dramatic
climate changes that were happening around the world, and specifically
changes that were happening in Africa, where our ancestors were
living at the time. And actually the reason there were

(48:44):
such dramatic climatic changes has to do with changes in
the tilt of the Earth. Right, So we are on
a planet that has a tilt of about twenty three
and a half degrees at the moment, but that tilt
changes over time and there's sort of fluctuations. And also
in the shape of our planet's orbit around the Sun,
it can be sort of more round or more stretched out.

(49:05):
And as you sort of put those two changes together,
you get time periods in which the climate is especially volatile,
in which you can have relatively rapid swings from really
wet to really dry, really cold to really warm. And
that type of change was happening worldwide, but especially in

(49:26):
Africa during this time period. And that is the time
in which we see this really dramatic rise in the
size of the cranium in different species of humans. So
we think that this was basically natural selection favoring greater intelligence. Now,
the correlation between brain size and intelligence isn't perfect, right,

(49:49):
Just because the grain grows larger doesn't necessarily mean that
they get smarter. I mean, the largest brain of any
animal species in the world is that of you know,
certain species of whales, which are they intelligent? Yeah, they're
pretty intelligent. Are they more intelligent than us? Probably not?
But in general, we do think that that increase in
brain size probably had to do with an increase in

(50:11):
intelligence to a certain extent. So it probably did have
to do with the ability to handle and cope with
those dramatic changes. I mean, if you're sort of living
out on the African savannah and just trying to feed
your children and not get eaten by lions, you know,
and you've sort of figured that out to a certain extent,
and then all of a sudden the climate completely changes, Right,

(50:36):
you have to figure out a new way to do
those things. That is really going to be a tall order.
So we think natural selection was really operating at that
time to help people to deal with those dramatic changes.
They had to work together, right, So part of what
we think is driving some of this change in intelligence

(50:56):
is the ability to communicate with one another, the ability
to work together to understand what another person is thinking
and maybe predict what the other person is going to do,
and as we all know, that's a hard thing to do.
So that intelligence would have been favored by natural selection
as our species was just having to cope with these
new challenges to our survival.

Speaker 1 (51:17):
There has to be something more than that, right, I mean,
I know that we don't have the whole picture, of course,
and I don't expect you to have the whole picture.
But like other species existed at the same times in
the same environment, and antelopes can't do string theory right
as far as I know. Maybe they are and they're
just not sharing the answers with us.

Speaker 3 (51:33):
Maybe string theory is maladaptive.

Speaker 1 (51:36):
Maybe having physicists is bad for humans. Is that what
you're saying. But my point is, beyond the only ones
to face that environment, we seem to be the only
ones to develop this capacity, not just to solve the
problems of that era, because you didn't have to be
able to do string theory to survive in those volatile circumstances,
but to do this crazy intellectual wrestling matches that we
do today. So it seems like there's got to be

(51:58):
more of the story, don't you.

Speaker 5 (51:59):
Think, Yeah, well, it is definitely true that, you know,
not all species became more intelligent during that time, So
what was it about us?

Speaker 2 (52:07):
Right?

Speaker 5 (52:07):
And I think one of the answers to that seems
to be that we already had a bit of a
head start. So if you look at the change in
brain size over the last like six million years, like
going back to the time in which we shared a
common ancestor with chimpanzees, there was already a trend towards
bigger brain size in some of the early human ancestors,

(52:28):
but then it really just sort of rapidly increased in
size during this period from around one to two million
years ago. So what was happening then, Well, that's when
you get these climate changes, So it's probably something to
do with that. Of course, we need a time machine
to go back and be able to tell for sure.
But the reason that other species didn't also become more

(52:48):
intelligent during that time probably has something to do with
the fact that they didn't have much genetic variation for
brain size or intelligence. So that's like a really key
thing to recognize is that natural selection by itself is
powerless unless there's some kind of variation that already exists,
that selection can sort of sift through and say, Okay,

(53:11):
this version is going to do a better job than
this other version. And do a better job just means
basically make more babies. At the end of the day, right,
evolution it's just all about babies and who's making more babies.
So if there were some individuals that happened to have
a slightly bigger brain, happened to be more intelligent, and

(53:31):
if that led to them making more babies, then you
know that was what became more common.

Speaker 1 (53:36):
I mean some ultimate universe where a population of humans
found a different strategy for surviving those vault of times
by being like really good climbers or super fast, then
we might all be Usain Bolt today for example.

Speaker 5 (53:48):
Yeah, exactly. Yeah, That's it's pretty stochastic at the end
of the day. And there's a lot of things that
could have gone differently that would have turned us into
a very different species or caused us to not exist
at all.

Speaker 3 (54:00):
I talked a lot today about different misconceptions people have
about evolution and human evolution. Are there any others that
you encounter when you talk to people about evolution that
are worth debunking while you're on the show.

Speaker 5 (54:11):
Yeah, I guess to me, the one that comes up
most often is this idea that just because a trait
seems like it would be useful, that we should expect
it to evolve, like where are my wings? Scott, Yeah,
exactly right. Or the one that I hear so often
is like, you know, hey, everybody's playing video games these days.
Does that mean our thumbs are going to be bigger
and stronger in the future, because you know'd be better

(54:33):
at playing video games? And my answer to that is, well,
do people, first of all, have variation in thumb size
and strength.

Speaker 2 (54:41):
I don't know.

Speaker 5 (54:42):
Maybe they do, but that would be one thing that
would have to be true. The other thing is that
the people with the big, strong thumbs would have to
have more babies.

Speaker 2 (54:49):
And that's where I have my doubts.

Speaker 3 (54:55):
So I've read both of your books and yeah, that's right.
I got to read his second book early. And I
get the sense from reading your books that you really
enjoy the travel that goes into researching the book. What
was your favorite research trip that you've taken for a
book so far?

Speaker 5 (55:10):
Well, first of all, Kelly, I love that you have
been willing to read my books, including in advance, and
you've given me some really great feedback and suggestions, So
thank you for that.

Speaker 1 (55:20):
Kelly is so good at that she is.

Speaker 3 (55:22):
Ah, thanks guys, It's my pleasure. I love getting to
read early copies of books.

Speaker 5 (55:25):
But you're right, I do like to travel, and so,
you know, one of the things that I've enjoyed in
researching that these books that I've written is traveling around
and you know, meeting people who are doing interesting work.
And I really enjoy being able to kind of describe
the work that someone's doing by kind of you know,
showing people how they do it, and you know, getting
to know them in their natural environment, so to speak.

(55:47):
So yeah, I mean I've done some interesting trips for
this book, Future Humans. I think the trip that was
maybe the most fun that I got to do was
to go to Quebec. And there's an island in the
Saint Laurence River with a French name that I will
not attempt to pronounce apologies to my high school French teacher,
but the reason is that this island is a place

(56:11):
where there has been a very interesting series of research
studies by a biologist named Emmanuel Milo, and I got
to go actually to this island with Emmanuel Milo. We
traveled there together, and what was interesting about it is
that this island was first settled by French Canadians in
the seventeen hundreds, and he and some of his colleagues,

(56:35):
Emmanuel and some of his colleagues were able to basically
trace the history of the human population on this island
and show that there has actually been evolutionary change among
the people living on that island between about eighteen hundred
and the nineteen sixties. So this is like, you know,
roughly sort of seven or eight generations of people that

(56:57):
lived on this island. And because it was an island,
because it's kind of hard to get to, it was
relatively isolated from the surrounding communities. And so what they
showed is that actually the age at which women had
their first child changed on that island from averaging about
twenty six years old to about age twenty two over

(57:19):
that time span, So women started having their first child
at a younger age during that time period. And what
was especially interesting about this population is that they had
a complete genealogical record of the entire population because of
church records, so everybody pretty much went to the same church,

(57:41):
and the church keeps track of births, deaths, and marriages,
and so because of that, they had this whole genealogy
of this population and they were able to basically rule
out that this change in the age of first birth
it could have been due to other factors. You might
imagine that it was like, well, some people might have been,
you know, richer or poorer, or had access to more

(58:03):
food or different culture, whatever it is, right, And basically
they were able to rule out all of those other
possibilities and show that in fact, it was a response
to natural selection. So basically natural selection was favoring women
starting their families at a younger age because women that do,
on average tend to have more children, and that is

(58:25):
actually something that is predicted from evolutionary theory, but it
had never been shown before in humans, particularly not in
a modern human population. So it was really interesting. It's
a beautiful place. They are lovely people. We got to
go and spend several days on this island and we
met a lot of great folks there, got to learn
a little bit more.

Speaker 2 (58:43):
About the history of the island.

Speaker 5 (58:45):
It was really interesting to go with Emmanuel Milo and
actually see this place that had been you know, this
subject of this really interesting study he had done.

Speaker 1 (58:54):
It's amazing how important islands are to the history of
evolution and our study and understanding of it. Right, We're
lucky we have islands.

Speaker 2 (59:00):
Yeah, it's true.

Speaker 5 (59:01):
I mean partly because they're sort of like these little
miniature versions of what are normally much more complex systems. So,
you know, going back to Darwin, right, you know, in
the Galapagos. I mean, biologists still go to islands because
they often helped to kind of reveal more complicated phenomena
in a somewhat simpler way.

Speaker 3 (59:19):
I also feel like if I could go back and
have a different career being a historian would be really
cool to just be able to like handle old documents
and see like old writings I don't know something about
like really old stuff. Oh yeah, it is really exciting.

Speaker 2 (59:31):
Absolutely.

Speaker 5 (59:32):
I mean one of the things that we did was
we actually visited the Archdiocese of Quebec and got to
see the archives where they actually had these original records
of birth, deaths, and marriages. We had to open up
those books and see for ourselves, and I get goosebumps
when I see that kind of thing, right, I mean,
it's just getting to have that immediate connection with history.

Speaker 2 (59:50):
I think it's super cool.

Speaker 1 (59:51):
That reminds me of the exhibit in the British Museum
where they have original manuscripts from famous people, so you
can see like Mozart's scribbles and Beethoven like crossing stuff
out and really fascinating to think, like that guy actually
wrote on this piece of paper. I don't know why,
but it is really powerful, right.

Speaker 2 (01:00:06):
It is. We actually at Rice.

Speaker 5 (01:00:08):
In our library collection, we have the collection of work
from a biologist named Julian Huxley, who is a famous
biologist in the early twentieth century. His grandfather, Thomas Henry Huxley,
was one of Darwin's closest friends, and there is a
copy of the Origin of Species in the library that
was given by Charles Darwin to Thomas Henry Huxley, and

(01:00:29):
it has both Thomas Henry Huxley and Julian Huxley's notes
in the margin.

Speaker 2 (01:00:34):
It's just the.

Speaker 5 (01:00:35):
Coolest thing to see. No, I still get chills thinking
about it. Yeah, it's so cool.

Speaker 1 (01:00:39):
Speaking of chills and connecting back to Antarctica. One of
the things they have in the British Museum is like
the logbook of one of these journeys to the South Pole,
and you can see like the last page where the
guy rights it is very cold, and then that's it.
That's the end of the law. Oh yeah, oh they
found him with it.

Speaker 2 (01:00:56):
Oh that's ominous.

Speaker 3 (01:00:57):
Is that the Scott expedition?

Speaker 1 (01:00:58):
Yeah it might have been yea, yeah exactly, but you
know he was taking data to the end a real scientist,
you know, keeping records. But now I want to get
to the inevitable place we always get to on this podcast,
because everything leads to aliens and wealism, and I want
to ask you about aliens because I want to know
if what we've learned here on Earth is particular to

(01:01:22):
our experience here where we tend to have islands and
we have this particular history, or if this is something
general and universal we've learned about life in the universe.
So we're landing on an alien planet and we brought
you along, Scott. Are you expecting to learn that on
this planet there's natural selection and this evolution or do
you think that that those are things that just happen
here on Earth because of our particular set of circumstances.

Speaker 5 (01:01:44):
Yeah, I love this question because it forces us to ask, like,
what is life? And do the things that we know
about life actually apply, you know, universally or only to
this particular version of life that we know. We actually
in biology struggle to even to find what life is.
And there's a lot of things that are sort of
like gray areas, like, for example, viruses. Right, I don't know, Kelly,

(01:02:08):
if you have opinions on our viruses alive, that's like
a way to start a fight at a biology conference, right.
But one of the definitions that people have proposed for
what is life is that life is capable of evolving,
and so like by definition, then if we see life,
then yes, it should be capable of evolving. But that's

(01:02:29):
like a circular definition, so it's not very satisfying. So
I think another way of thinking about it is unless
another form of life is immortal, if it has immortality
and one individual can just live forever, then no, they
wouldn't evolve the way that we think about it. But
as long as there is mortality, as long as there

(01:02:50):
is death, and as long as there is reproduction, and
as long as there is some way for individuals to
pass something of themselves to their offspring to the next generation.
In that basic setup, you will always expect natural selection
to work. You would always expect the basic principles that
we've been talking about of evolution to work, and that,
to me is one of the most powerful things about

(01:03:12):
it that I think people don't often realize. We're not
just saying evolution can happen, or you know, under some
circumstances you might get changed. No, it's actually inevitable. It's
sort of built into the system that anytime you have
a thing that lives for some amount of time, reproduces,
passes something on somehow to the next generation, right, that

(01:03:34):
there will be changes that are heritable that are happening
from one generation to the next. Now, the specific things
that are evolving, the traits, the rules that maybe govern
who survives and how they reproduce, that's all up for graps.

Speaker 1 (01:03:47):
The biochemical mechanism, whether it's DNA or.

Speaker 5 (01:03:49):
Not, yeah, exactly, doesn't have to be DNA, doesn't have
to be anything like the way genetics works for Earth life.
But as long as there is some mechanism of inheritance
and as long as there is reproduction and multiple generations,
there will be evolution.

Speaker 1 (01:04:06):
I like that you're very clear about the assumptions that
go into that conclusion, because that immediately opens doors for
like potential science fiction stories like I imagine now a
planet where abiogenesis is very common. It didn't just happen once,
but it's like constantly happening, and you're always getting like
new forms of life propping up and they don't reproduce,
they just die out. I guess in that scenario, you
wouldn't have evolution, right, you just have like a constant,

(01:04:28):
random genesis of weird kinds of life.

Speaker 5 (01:04:30):
Yeah, And that is an interesting thing that I often
think about, is how come we only see the evolution
of the origin of life one single time right here
on Earth that we know of, or at least only
one lineage of life has left descendants that we can
find today. Why doesn't it keep happening? And I think
there's reasons for that that we think we understand, But yeah,

(01:04:50):
it could be that in some other world that it
is much more common for life to just pop up spontaneously.
And yeah, and that circumstance each individual origin of life
could give rise to separate sort of evolutionary trajectories. But
we would still expect them to evolve if they could reproduce.

Speaker 1 (01:05:10):
Eventually they would end up with podcasts, right.

Speaker 3 (01:05:14):
Everyone podca can hope that's right. Everyone on the show
today has.

Speaker 1 (01:05:19):
Their own podcast, therefore dot that's.

Speaker 3 (01:05:24):
Right, all right, Well, Scott, this has been amazing and
informative and a ton of fun. And thank you so
much for being on the show. And we plan on
having you back to talk about the future of human evolution,
which is the second half of the question that we
got from the listener, what would happen when our species
moves out into space? So we look forward to having
you back when you are ready to talk about your
next book.

Speaker 5 (01:05:43):
Well, thanks so much, Kelly and Daniel. This has been
fun and I can't wait to come back.

Speaker 1 (01:05:47):
Thanks for evolving our understanding of biology.

Speaker 2 (01:05:49):
Oh anytime.

Speaker 3 (01:05:58):
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