Kind: captions
Language: en
Could you take embryionic hakee, stick a
needle in me, change a instruction, and
I now have fangs [music] and venom?
[snorts]
Yep. [laughter]
[music]
>> Sean Carol, welcome to Particles of
Thought.
>> Thanks for having me. Yeah, I'm so happy
to have you here, man. So, you are an
evolutionary biologist and you study the
evolution of new species coming into
existence. And when I hear that, I think
about us humans. We've changed a lot in
a very short period of time. What are we
going to evolve into and when?
[laughter]
Boy, wouldn't we like to know? Yeah,
it's hard to predict the course of
evolution because there's a lot of
ingredients that go in. You know, for
most of the story of
>> life on Earth, you know, the earth
changes and life changes along with it
>> and you know, we're creatures of that.
We're kind of creatures of the ice age.
Um, but then we've started to control
our own environment and that's now we're
we're kind of in a whole different
realm. Uh, I would say, you know,
because we get along we get across the
globe relatively easily. We mix with
each other very easily.
Um, you know, I think our future is
going to be of one one big kind of
intermixed population. That's real real
different from the past when you would
we had a lot more isolation, you know,
people on islands, people living at high
altitude, all that kind of stuff. And
that that would make
>> that makes us all look more different,
>> right?
>> I think in the future we're that one
that that gene pool is all mixing. So
maybe we're going to be a little more
similar to one another.
>> Yeah.
>> And uh but I don't I don't see any
superpowers coming. I
>> No. Well, I'm just hoping we don't lose
what we already got, which is, you know,
libraries, the scientific method, you
know, little things that help us cope.
>> Well, according to Stan Lee, right, we
evolve into homo superior and we do have
superpowers. Yeah. Before we get too
deep into the conversation, you know,
we're using terms and, you know,
sometimes we say phrases all the time
which makes us think we know what we're
saying, but actually we don't. I've
experienced this in my field with the
phrase big bang. And I think when people
hear a word like evolution, a lot of
people go monkeys to humans, right?
[laughter] Not happening. Let's go into
what evolution really is and how it
really works.
>> Sure. Evolution is change over time.
>> That's it. Just just just let that
settle for a second. That's all it
really is.
>> Okay?
>> Change over time. So you can think about
those two things. What's what do we mean
by change? Well, that's change in
appearance, change in the properties of
something, right?
>> Um, and time, time's a big ingredient.
Yeah.
>> And time is really the hard thing that
>> for people to get their heads around.
And Darwin really appreciated this
because in his day
>> where the entire mindset was one of
creation or essentially instantaneous
creation of things. He had really two
big challenges which was to get people
out of that mindset to understand that
natural processes were sufficient to
explain what you saw in the world and
that there had been immense amounts of
time available to do it
>> and these were big scientific gaps right
and even Darwin who thought oh maybe the
world was as much as 300 million years
old I mean he was off by a factor of 10
right there was a lot more time than
even
>> Darwin realized okay so let's just start
with change over time and we can break
that down in any direction you want. How
does the change happen,
>> right?
>> And then, you know, small amounts of
time, big amounts of time, you know, the
degree of change is somewhat going to be
proportional to time, right?
>> But, you know, things can change
rapidly. If things on Earth have changed
rapidly, you'll you'll see rapid
evolutionary change. If the Earth is
fairly stable, you'll see relatively
gradual evolutionary change.
>> Oh, interesting. Interesting. Yeah. I
know there was that geological time
that's called the boring billion just
before the Cambrian explosion. So does
that mean that geologically things were
boring? So life was boring?
>> No. Well, I mean I think any geologist,
you know, sitting here would say nothing
was nothing's ever been boring about the
planet because the planet has changed
tremendously.
>> Um especially things like oxygen levels
and and the sort of which means the
metabolism of life has changed a lot.
>> I think the boring comes from just our
perspective which is life was really
small. Life was micro microbial for
those billion years, right? So if you
visited Earth from somewhere else during
that billion before the Cine, you kind
of look around, you go, "Okay, I I see
some algae. I see some bacteria, you
know, next." Okay, [laughter]
>> but we're animals, so we get excited by
bigger things, right? And animal
evolution really kicks into high gear
and the Cambrian and then when life gets
to land, of course, then you get, you
know, plants and trees and all this sort
of stuff and the world that's, you know,
much more familiar to us. So, right,
>> you know, it's uh that perspective
depends upon maybe what kind of creature
you are. If you were if you were a
cyanobacterium,
>> you know, a billion and a half years
ago, the planet was wonderful. It was
paradise.
>> Yeah. Now, it's kind of [laughter]
>> now I got to share it with all these
clowns. Yeah. Yeah. Yeah.
>> And feed them their oxygen. And so,
>> the idea of new species evolving, like
it's pretty obvious when a species goes
extinct, there's no more of them. How do
you know when a new species has become?
>> This is a great question. This is a
tremendously great question. I think you
know we kind of grow up getting species
a concept of species sort of very static
and very like as though these are
categories that are very cleanly
delineated and that's it and there's no
mixing or anything like that. But that's
not the case. In fact, I just saw in the
news it's a really cool story about the
green jay and the blue jay. Green j for
Mexico. Blue Jay is familiar to us in uh
here in the United States.
>> Hybrids have been observed in Texas and
the hybrid doesn't look like exactly
like either parent.
>> So when these groups can come in contact
even though we would have called them
separate species,
>> you can get hybrid forms.
>> Okay,
>> that's not like a cement wall
necessarily between one population and
another. It can be a leaky barrier.
>> Right
>> now, let's go to the speciation process
itself. when it's happening, how can you
tell when something is split into two?
Because you got to realize
>> that those things are those populations
are probably so difficult to distinguish
from each other.
>> So if you take something like uh a
mountain range or a river that might
>> a lot of species form because of
isolation between populations. Okay, so
let's back up a little bit about process
and say all right
>> mountain ranges or you look on different
islands or something like that. So if
you start out with two populations that
are really similar
>> and given time there's been isolation
between them that they live on opposite
sides of some kind of barrier.
>> How do you know when they're different
species?
>> Yeah. What is that when does that switch
flip to
>> and it's not it's not a switch because a
I tell you it's a leaky barrier and and
second it depends on time
>> and is there a little bit is there just
a little bit of intermingling between
them which will sort of keep those
barriers lower. So you know we humans we
like to classify things. So of course
it's useful to classify things as
species but we don't want to give people
a hard and fast idea that these things
are sort of some kind of absolute you
know you know totally self-contained
population because they can mix.
>> And then in that process of speciation
it's a gradual separation of populations
one and two. So speciation is splitting.
>> Yeah.
>> One becomes two.
>> Right.
>> And that's happening all over the tree
of life. Right. Yeah.
>> Um, and it may be driven by different
conditions that the two populations
experience. So maybe think about maybe
up a mountain side, the things that are
adapting to maybe, you know, near or
above the tree line are different than
those that are living below the tree
line and eventually they sort of divide.
We can see that happening with things
like insects and all that.
>> Um, but uh, you know, no biologist can
walk in and say, well, this is the day,
you know, this is the day the species
happened. It's a gradual change. And for
some population, say animals, you know,
it might be a a two million yearlong
process of essentially becoming so
distinct that there's no going back.
>> You just gave me a movie in my mind of
of a of an experiment where you have
these two you take one species separated
on two islands, then you have
generations of scientists observe them.
>> Yeah.
>> And then you can say, "Aha."
>> Yeah. on July 8th, 2027.
Like, but even if you were to do that,
would you do it based on taking two
members and seeing if they mate? Would
you do it based would you figure out
that they were different species by
looking at their genetics? Like, how
would you figure that out? I I think
functionally we'd say two things. If
they wouldn't mate, okay, then that's
it. They're separate. There's no there's
no putting things back together if they
won't mate. or if they mate and their
offspring are inviable or infertile.
Yeah. Then that's it. Okay.
>> But often the case is going to be I my
prediction is this. Let's say we'll do
this with two birds on islands. It's
kind of been done a few times in
[laughter] nature. All right.
>> Yeah.
>> And those scientists are on those
islands a long time.
>> 10,000 years, 50,000 years, 100,000
years. I think when you do that
experiment, they're still going to mate
and their offspring are still going to
be viable. 200,000 years, 300,000 years,
400,000 years, somewhere maybe half
million years, million years. Okay. Now,
maybe they start to they their behaviors
are different enough they're not going
to mate or they're genetically distinct
enough that if they do mate, yeah, the
the offspring aren't viable. So, that's
that's the long gradual ticking of the
of sort of the clock. And what do we
mean by the ticking of the clock? Is it
under isolation,
>> you know, mutations happen in
populations,
traits change a little bit, etc. So
eventually either behavior or biology
may be different enough that you can't
mix them back together again.
>> But there's a long window where things
are permeable, right?
>> Yeah.
>> And you know taking you started out with
a question about us. You know, one of
the most mind-blowing discoveries of the
last 20 25 years
>> was the Neanderl contribution to Homo
sapiens, right? You know, so for a long
time we thought, okay, here's our
species. We're different from everything
else, right?
>> Yeah. But now we know
>> there's a little bit of Neanderl in most
of us, right?
>> Yes. Exactly. So it's a much more
complex
>> um history than just split split split.
You know the the the convenient picture
of the tree of life is
>> you just keep splitting species, you
know, one and two, one and two, some go
extinct, some keep going, etc., etc.
>> But those splits, they come back into
contact. And why do they come back into
contact? Well, they come back into
contact because we have a changing
Earth. Think about the ice ages here,
okay?
>> How many times in North America ice
sheets have covered North America,
right? So that's going to drive life
into into refugeia, right? Into places
that aren't that aren't ice covered,
right? And things are going to be mixing
and then
>> the the sheets retract again and things
spread back out again and you know and
this population's on one side of the
Rockies and that you know some somewhere
else and then here comes the ice again
back in. So with a changing planet,
you're going to have populations driven
apart and populations driven back
together again. So speciation is we'll
just call it sloppy.
>> Yeah. And not only that,
>> it's not a clean cleaving of one into
two.
>> Yeah. And the other thing that you just
pointed out how these geological changes
drive that. And since the time of Homo
sapiens sapiens having civilization,
we've been pretty stable, right? We
haven't we haven't had major geological
upheavalss like super volcanoes and ice
ages hitting us. So what we think now is
a normal
>> is not really a normal.
>> Yeah. It's in a short little interval,
right? I mean
>> the last you know civilizations the last
10 or 12,000 years
>> or at least you know farming and
domestication and all that kind of
stuff, right? But our species is 300,000
years old.
>> So they saw it.
>> They saw some serious stuff and they've
been through bottlenecks. I mean,
>> yeah,
>> we may have been down to, I don't know,
maybe 1,200 breeding pairs.
>> That's what I've heard. Yeah. Around
900,000 years ago, we're down to like
1300.
>> Yeah. Under some climate duress.
>> Let that be a lesson to us all.
>> Yeah. It lasted about 100,000 years. But
it also talks about our resilience. We
We made it through that. And you know,
>> we're a we got a lot more technology
than those hippies,
>> right? I [laughter] mean,
>> yes. Yes, we do. We absolutely do.
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So there have been a lot of transitions
that have occurred over life. These
stories that we hear, right? Going from
land to air, animals going from sea to
land and back to the sea. There was even
this idea that humans were water
monkeys. [laughter] Remember that idea.
Yes.
>> Uh
>> occasionally comes up in seminars I
give. But uh
>> Oh, no way. Yeah. Yeah. So, how do these
transitions happen and how long do they
take? If if a if if if walking a
tetropod is going to become a whale
>> or seal and then you have animals like
otter that are somewhere in between, you
know, how how does that
>> Well, it's a paleontologist, so that's a
different branch than myself. I'm not a
fossil hunter. You've had you've had
you've had a
>> So, that's where that story is written
is right.
>> Yeah, that story is in the fossils. And
um you know I think it's reasonable to
think I I think the estimate let's look
at a big one. Let's let's look at um
backboneed animals coming to land. So
fish
>> to land right going from fin to limb
walking on limbs
>> that takes longer and a lot of
speciation events. You don't just go
from being a fish to an amphibian in one
step. You don't go from being you know
ground dwelling to flying in one step.
>> Right? And you know roughly speaking
from the fossil record of various things
I'd say you know 10 15 20 million years
to execute a change like that
>> because there's a lot there's a lot of
anatomy changing. If you look at all the
remodeling of the skeleton and you're
going from something that's very
flippery to something that we think is
you know a little more digity you know.
>> Yeah.
>> Yeah. Takes a while. But
>> the paleontologists are out there
looking at for the fossils that sort of
mark that transition. And this has been
again really an exciting time. It's been
a golden age for paleontology to
>> Well, it makes me think of the the the
animations you see. You know, the
animations show a little fish and then
they like come up on the land and then
they transform into an amphibian, then
they transform into a reptile and Yeah.
You know, each of [clears throat] those
steps is
>> that's sped up. Yeah. [laughter] But,
you know, you we know there are
creatures that will live in the shallows
and then maybe do a little air
breathing, right, when they're in the
shallows. And you can start to imagine
because other things are happening. It's
not just the limbs that are changing.
For example, yeah, remember they got to
breathe air. Yeah.
>> So they got to go from gill to lung.
>> Yeah. So a lot simultaneous.
>> Yeah. A lot of things are changing. And
then probably you're seeing the position
of the eyes and the head changing from
maybe being out here
>> to being up top or being facing forward.
>> Recently was the limbs that spllay out
to being directly underneath.
>> Yeah. You got to support because you
come gravity is different, right? You
come on to land, you got to support that
whole body
>> whereas you're floating water otherwise.
>> How does it happen then? So all of these
changes of l gill to lung, fin to limb.
Yeah.
>> Uh and I would imagine if you are in
water then there's some sort of
balancing act with salinity that your
body has to undertake.
>> Physiology is changing etc. Yeah. So so
how do those
>> diet's going to change right the whole
thing right? What you're going to eat is
going to change the whole thing right.
Yeah. In fact it might be food that's
driving you onto land right. sometime of
scarcity you start finding there's stuff
on land
>> or you are the food
>> or you are the food let's get out of
here
>> absolutely let's get out of here
>> like the flying fish or something like
how
>> those things are driving things but
>> what what what drives that from the
inside so I I so the story of evolution
is you have some advantage to become an
adult and reproduce so you pass that
trait forward that's right
>> right and so there's going to be some
variation in that trait ac across that
species so is it the case that It's very
slow although you it's fast to you or
does it happen that these mutations are
occurring and then a mutation occurs and
hey look look we suddenly made a leap
>> it's not very leapy you know I think 100
years ago we entertain the thought of
things could be kind of
>> uh could move in jumps like that but
it's it's it's really not like that when
we really break down these transitions
it it's a lot of anatomy that's changing
that's a lot of physiology that's
changing right
>> and it's happening in increments and at
the increment isn't like, oh, this
generation is, you know, 1% better, the
next generation's 2% better. That's
that's even pretty fast.
>> There's going to have to be a lot of
concerted changes. And we also see when
these things are happening, lines go
extinct. You can see something kind of
getting there, but that branch doesn't
make it. It's something else that does
better and and is, you know, a more
direct ancestor to what we finally see
on land and things like this. So, it's a
process ridden with extinction because
in 10 million years,
>> there's a lot of extinction. You know,
probably most species only last a
million years or two.
>> Oh, wow.
>> So,
>> well, is that Wait a minute. So, there's
there's two ways to go extinct.
>> It's not a oneway I just want to get
this picture. It's not a one-way street
that
>> that line that starts to make its way
onto land. That's, you know, that's like
a, you know, a super lineage or
something like that. No, it's going to
it's going to experience extinction as
well. Branches are going to die off,
etc. It's a it's a messy process. So
what about something like a mental
change? So apes going from uh you know
from oropythecus to homohabilis and now
you're making tools and you're designing
tools and you come up with multi-art
tools like how does that you know
>> that's a great one boy wouldn't we love
to know a lot of those details right but
look what we do know you know two and a
half million years ago or so we're we're
starting to to make tools
>> that's fine motor skills
>> right and um we're living a more
visually driven lifestyle so one thing
you can relative to other mammals is
that like our visual system is we we
dedicate a fair amount of brain space to
visuals and for example less to scent.
Yeah.
>> So if you look at compare it with
mammals that um may make their way along
the ground you know even our favorite
companions like dogs etc. They're
devoting a lot of brain space and a lot
actually of genome
>> to the things that are going to help
them smell their way through the world.
We're kind of seeing our way through the
world. So, is it because we're upright
because you you you made this this
relation to the ground?
>> We're we're upright. So, we're away from
kind of odors as much, right? Because if
you're living, you know, close to the
ground and if that's where your food is
and you're trying to find scent trail,
that's where your mates are,
>> right? So, just I mean, whether you
think of a rodent or a canine or
something like that, close to the ground
kind of smelling its way through the
world.
>> Um, you know, look, we use dogs to
detect things. They're they're so much
better at it than we are. Well, they've
got a bigger repertoire of um receptors
for smell and they devote more of their
brain space and um to to uh detecting
these smells.
>> Well, we've adopted a different
lifestyle. We've actually given up a lot
of the
capability of for smell that existed in
more distant ancestors.
>> Yeah,
>> you can ask me later how we can see some
of that those vestigages. And we're
living a more visual lifestyle. And the
great apes have full color vision,
right? So we're we're we in the
>> Is that unusual?
>> Very unusual. So our other mammals don't
have it. Okay. So we there was a
evolution
I'm gonna go 25 30 million years ago
where we picked up uh another light
receptor in our uh in our retinas but it
connected to our brain. So we can
distinguish for example red, green,
blue. Mhm.
>> Well, really useful when you're like
grazing on leaves in the jungle and you
can tell the ripe ones from the unripe
ones, etc. Okay.
>> So, we see in full color.
>> So, this our we're more, as I said,
we're more visual species.
>> Yeah.
>> And we've traded off that that sort of
smell driven, old factory driven uh
lifestyle. And so, when you say, you
know, about change, this is manifested
in all sorts of ways. is you know in the
brain how much is dedicated to visual
processing versus old factory processing
in the genome a mouse or a dog might
have a thousand genes for scent
reception
>> where we've inactivated hundreds of them
you actually still see them in our
genome so in other words we know they
were there in our ancestor and these are
like little fossil texts they're like
they're like little redacted text almost
there but with mistakes in them that
have accumulated over time and it's a
great it's a really cool way to sort of
look back at our past is that there are
fossilized genes in our DNA and that's
telling us about lifestyles of our past
ancestors.
>> So if by some alien invasion or
something like that we find like oh we
better keep your head below 4T off the
ground we still have that ancient genome
in us to go back to smelling
>> we'd have to do some repair we'd have to
do some repairs. Yeah, which of course
now we have technology to do those
repairs to change our own DNA. But yeah,
it it's uh these these the lifestyle of
creatures and the lifestyles of their
ancestors. This is something again that
that we sort of didn't imagine decades
ago is that in DNA we we can see the
vestages of the past may not be used
anymore, but it's some of that text is
still there in the DNA. And it's a
really cool clue to look back and say,
well, what were our ancestors doing that
we're not doing anymore?
>> Well, what about like conversion
evolution? So there there are many
species that fly. So we have insects
flying, we have uh had flying reptiles.
Yeah.
>> We have flying mammals. So all of these
>> created a wing of some sort, right? Not
necessarily the same physics with each
one. No.
>> So it it how does a wing So I'm a
tetropod. Yeah.
>> But now I feel like I need to fly. How
do I go from
>> uh you know being me with arms to me
with wings? Well, they've all done it
differently. So, terasaurs, the dinosaur
you're referring to.
>> Yeah.
>> Uh, and birds, which of course were also
flying reptiles essentially.
>> And, uh, bats,
>> the anatomical details are all
different. Now, they all had to create
this
>> surf. They had to create some kind of
surface, right?
>> The the the part of the gene that
activates these.
>> They've all done it differently.
>> Okay. But they've all modified their
forearm. Okay. So, they've all worked
with this. Yeah. Okay. But where they've
made the webbing essentially to create
that wing surface is different. So, um,
you can sort of do this out more on the
hand. You can sort of create maybe a and
I got to think of my details a little
bit. I'd have to almost check this. Um,
but bats, birds, terasaurs, and this is
why we know they they're they're all
independent inventions is that when you
kind of look at the design of the wing,
they're they're using different pieces
of the forearm anatomy to to create that
wing surface. Okay. So this is the you
you're inventing a wing. Yeah.
>> You're working from a similar starting
point.
>> But it turns out they engineered three
different pathways
>> bats, birds, and terasaurus to to make
wings.
>> Now the the origin of novelty that the
general thing that I'm interested in,
lots of evolutionary biologists are
interested in is okay. Well, that's cool
to look at the finished wing and go,
"Wow, look at that. Terasaurus, amazing.
Bats amazing." But how does that even
happen?
>> Yeah. How do you get there?
>> Okay. How do you get there?
>> This is a question that it's really
central to evolutionary biology. It
worried Darwin from the start because
he'd look at these things and he'd say,
"Well,
you know, his description of evolution
was this very incremental process." And
if you think about something like an eye
or a wing, well, what good is half a
wing or what good is, you know, half an
eye, right? Uh how how do you so how do
you get there? So you have to start
thinking about maybe it was first a
little bit of membrane. It was a gliding
surface, right? Until you before you had
powered flight, right? And we think
about things that glide like there's
squirrels that are glide. There's snakes
that are glide for goodness sakes,
right?
>> Oh jeez.
>> So So we have to we have to sort of
either think our way through what the
value of sort of intermediate stages
would be. And of course the
paleontologists are trying to help us by
actually finding the fossils that tell
us what these intermediate stages look
like. Right? So that transition from fin
to limb looks pretty good. From to wing
is a little bit tougher like like
batwing. I mean those are tough fossils
to find like bat fossils or or bat
relatives and things like that.
>> We've got tons and tons of bird fossils.
>> Um which uh I I think we and we got a
pretty good story about feather
evolution, right? Because we think
>> here's here's another thing I'll just
jump into. You know, when we think about
feathers, we think about flight,
>> right? But you may now know from finding
dinosaurs that didn't fly but had
feathers.
>> Oh, feathers came before flight.
>> So, let's think about that one for a
second, right? Because again, humans
come in, we think like engineers. We
think, okay, I want to get up in the
air. How do I get up in the air? Let's,
you know,
>> we we design it, right? But that's
evolution,
>> you know. No, no. Evolution has to kind
of improvise its way there, right?
>> And [snorts]
feathers are just a great
>> illustrator of the evolutionary process
because they weren't there first for
flight. They were probably there for
either insulation, maybe a little bit of
>> um display, maybe a little bit of
camouflage, etc.
>> But as you start making these flaps or
whatever, now you got something out
there that can catch the air and then
you start to, you know, you evolve
flight feathers. You're like,
>> so feathers are a great illustration of
this thing of often
>> in biology there's this process we call
co-option. It we use something that
first existed for some other use,
>> right? and co-opt it into another
purpose. Yeah. So, evolution has to work
with the materials that are already
there, right?
>> It doesn't get to invent them from
scratch, right? In fact, evolution
doesn't work from scratch. It always has
to work on the pre-existing materials.
>> And so, it over time,
>> not even via mutation, not even via
mutation.
>> No, but no, mutation is it. So mutation
is the fuel that gives you
>> like could you could you for example
like uh have a mutation where suddenly
your kid is born and it has feathers.
[laughter]
>> It's a big step
>> or a feather-like
>> you could have a kid. It it's it's more
about if you already had for example if
you already had some kind of
feather-like structure
>> yeah you could have a kid with feathers
all over. Right.
>> Right. Okay.
>> But to create a feather out of nothing
>> Yeah.
>> is tricky.
>> It's not going to happen. What about
what about getting rid of something?
Because if we we look at the transition
from fish to land animals for
vertebrates,
>> the fish probably had a dorsal fin.
>> Yeah.
>> So, where dorsal fin go, right?
>> Stuff goes away all the time. That's a
great question. That's a great question
because
>> we often think about evolution being
this process of accumulation of new
stuff coming. We're getting rid of stuff
all the time. You may notice,
>> where's our tail?
>> Yeah, exactly. It's gone.
>> Right. It's gone. Right. cuz all our
relatives that have tails, right? So,
we've stopped that part of the
developmental process, we we we have the
capability to make a tail, but we don't
make it. Okay.
>> Um, so this goes on in evolution all the
time. Loss of stuff.
>> Do you think the loss is it more common
to lose than to reurpose?
Yeah, I probably I'd probably stick my
neck out and say that that loss is going
on all the time because as conditions
change, it's essentially a case of use
it or lose it.
>> Is there is there so there you think
there's some efficiency principle
underlying our design.
>> Yeah. Or the design of animals.
>> Yeah. Yeah. Because either making that
body part comes at some cost or
operating that body part comes at some
cost. So if it's not contributing to
performance
>> Yeah.
>> then here's the logic. mutations that
start to inhibit its formation or reduce
its size or whatever.
>> Those things are either of no cost to us
or they're actually beneficial because
we're not wasting
>> energy.
>> Yeah.
>> Building things that don't affect our
performance. So these things go away,
right? They go away over time. So
evolution sport, we can't plan for the
future, right? So we don't we don't we
didn't hang on to our tails just in case
we might need them. Okay? [laughter]
Right? It can't it can't wait. It can't
change that. It's it's all sort of being
weighed in the moment.
>> So things that enhance our performance
or are important to performance, we
retain. That's that natural selection
happening.
>> But things that don't affect performance
um survival, reproduction, etc.
>> Those things those those things go away.
>> Yeah. Yeah. So um loss is really common
when we look um you know through
evolution. I mean, you know, look at
things that creatures that are kind of
marked by loss. One of my favorite
groups are snakes, right?
>> Oh, the legs.
>> Where are those legs,
>> right? Well, they became burrowing
creatures, a whole lifestyle. So, they
evolved from lizards, right? So, they
evolved from four-legged animals, but
you have this whole group of animals.
They just
>> ditched their legs, right? Ditch their
ears, too.
>> Oh, geez.
>> No ears on snakes either, right?
>> So, um, yeah, loss is pretty common.
pretty efficient.
>> Snakes are pretty efficient.
>> They just reduce themselves to a tube.
>> To a tube. They're a tube. Yes. With
great muscles,
>> but they've been doing a lot of
inventing. Yeah.
>> Venomous snakes.
>> Venom. Yes.
>> Venomous snakes. And are have been
incredibly uh creative in the last 30 or
40 million years, inventing all sorts of
venom toxins to take down their prey.
And that's another example we see
throughout the animal kingdom.
Independent examples, right? You know
about spider venom, you know about bee
venom, you know about scorpion venom,
you know about, you know, uh, venomous
jellyfish and stuff. All independent
inventions.
>> Wow.
>> Of venom. So these are new molecules
that get invented, right? So this is
inventions going all the time, but that
helps those animals get their supper.
And that's a really powerful force in
evolution, right? If if this if you have
a way to get your prey, you have a way
to get food, this is a really this is
like evolution almost in uh fast
forward.
>> So language for humans is like venom for
the other [laughter] animals, right? You
can cooperate and hunt.
>> Well, in our culture today, language is
very much like venom. Yeah. But I think
you're making that analogy. But yeah,
these are this is uh you know, venom is
a special power that these animals have
and it's vital to essentially their
their daily being. And you know,
language is something. Yeah. We came up
with walking on two legs and and
language.
>> Uh pretty big inventions. You bet. And
you know, and vocalization,
>> right?
>> You know, to make that language.
>> So, let's dig a little bit deeper into
these transitions. So, the you know, we
have the transition of vertebbrates
going from sea to land. So, you know,
sometimes I come up with a crazy idea.
It makes sense to me and then I look it
up later, right? So, my crazy idea I
came up with was, hey, we have a tube
that goes from our mouth to our butt.
We're all worms. We just evolve, you
know, this extra stuff around the tube.
But then I went and looked where did
vertebrates come from. And the story was
something about some filter feeder that
um decided not to become a adult. And in
his laral stage, it was like a little
tadpole. Then it became the first um
cordate that eventually became something
like a lamprey and then a backbone. and
then on to land. It's an amazing story.
>> It is an amazing story. Yeah. Though
those early stages of of of backbone
creatures, you know, a little harder to
trace, you know, again, it's how good is
the fossil record. As we get a little
bit later, the fossils are great. You
know, the fish record and then the fish
that transition to land record. Thanks
to some brave paleontologists out there
who've gone to the far corners of the
world, we have a lot richer fossil
record now than we did just say 25 or 30
years ago. Really?
>> Yeah. Oh, yeah. Oh, yeah. No, we see
this in much better detail than we had.
Yeah. So, I think probably the
breakthrough fossil was something called
Tik Tok discovered by Neil Schubin and
his
>> tick tock.
>> Tik Talic. Tik Tok. No, no, it's
[laughter] not had nothing to do with
the social media app. Uh it has to do
with Inuit language. It was out of honor
to the Inuit. It was named um Tik Talic.
And it's uh this was a fossil discovered
in the Arctic. Um, that is just if you
had to draw a transitional fossil
between fish and four-legged animal,
this is it, right? This is what you
would essentially dream up. Sort of a
composite, right? Uh, or if you have
it's we call them fish and tetropods,
four-legged animals, tetropods. You
could say Tectalic is a fishopod.
>> Before I go into the detail, let me just
give you the significance of this, the
big picture significance. When Darwin
wrote the origin of species, he knew
that his theory had a lot of
predictions.
>> And one of those predictions was that
there should be intermediate creatures
out there between the great groups of
animals.
>> Yeah.
>> But he didn't have any.
>> I mean, he was essentially staking his
theory. And he in his book, he admitted
he said, "If these aren't found, you
know, my theory would be crushed."
>> Well, that's great science. He presented
his own falsifiable.
>> Absolutely. And this is what made the
origin of species one of the most
remarkable scientific works ever is
because he analyzed explicitly all the
weaknesses of his own theory. Like
where's the evidentiary holes right
>> now? Amazingly two years after the
origin of species somebody found this
creature out of a quarry in Germany
called archaopric you may have heard
about which had reptile characteristics
and bird characteristics. It was a
beautiful fit for Darwin's theory. And
it was 150 years almost 150 years later
that Neil Schubin and his colleagues
after a lot of searching find this
creature in the in the Arctic um that
has uh transitional features. It's its
eyes are more on the top of his head as
though it's kind of looking, you know,
looking up as opposed to looking, you
know, side to side a little bit. But
there's changes taking place in its
limbs. And so to come to land um the
fish lifestyle has to change quite a
great deal. It needs limb. It needs
those limbs to bear the weight of the
animal, right? Because it's up on up on
all fours as opposed to floating in
water.
>> Those articulated digits as opposed to
just a flipper that you could imagine is
clumsy. If we look at things like seals
on land, right? They don't look that
com. They don't look that agile. Right.
Okay. Right. But you know if you have a
much more mobile
>> so it had
>> Yeah. It has un it had the skeletal
makings of the digits. That's what we
can see in what we see in Tectalic is
it's a transitional creature. It's not a
full-fledged walking around tetropod but
it's heading that direction. That's what
we can see about it.
>> Um it's uh it has a neck that can move
relative
>> fish.
Yeah,
>> it's got a neck. How about that? Right.
>> So, that's where those are sort of the
giveaways if you're you're you know,
it's definitely not a fish. It's not a
full-fledged, you know, full-fledged
walking four-legged animal,
>> but you can see it head in that
direction. That's why it's such a
remarkable what we call these
transitional fossils because it's really
marking a big transition between two
groups. We're not talking about between
two species. We're talking about fish to
four-legged animals. One of the big one
of the big transitions. If I could just
insert here, you know, when people um
criticize evolution, you know, they they
want to disbelieve it. They will point
out, they say, "Oh, we see micro
evolution, yes, but not macro
evolution." So, what you're describing
is what they would describe as
macroevolution, evidence of macro
evolution.
>> Yeah. You're seeing the big transitions
between the big groups, the big
classifications, right? The big
categories in this case of animals,
you're seeing this these transitional
forms. So I'm I'm just describing to you
the that the
features of this creature that so tell
you a little bit about its lifestyle and
how is it different from a fish and how
is it different from a four-legged
animal? But the evolutionary process is
also what's going on? How do you change
your body?
>> Yeah.
>> How does the body evolve?
>> Right.
>> Now this is a really interesting area.
Again 50 years ago couldn't have said
much.
And that's because the process of
development, the process of making an
individual from an egg to a complete
individual was a black box. I mean, we
could we could watch it maybe in a, you
know, under a microscope, watch a frog
egg develop or something like that. But
we were just spectators, right? We were
just
>> You're talking about at the process of
egg. Yes. Embryo.
>> Yes. All the way to animal, right? All
the way to whether it's, you know,
juvenile or adult animal.
>> That process we could watch it, right?
you know, with
>> I guess what I'm getting at with that
question is is all of this baked in at
those very earliest stages because, you
know, we talk about how humans have
gills in the womb, right, when we first
start and and this sort of thing, but
ultimately we become a full-fledged
human at some point.
>> That's right. That's right. So, that
developmental process and I let's just
take a second to to to appreciate this
because it's almost like it's an
everyday process going on around us. If
you've seen, you know, you mentioned
frog eggs, you know, you see a frog egg
in the pond, you know, that's about to
be one of the most spectacular
pageantss that exists on Earth. The
making of a complete individual from a
single-sellled egg
>> is remarkable. I've watched it millions
of times never bored me once. Still
remarkable. And of course, anyone who's
gone through, you know, having children,
oh yeah, you know, and you sort of
imagine all those stages and if you're
watching the ultrasound, you're like,
"Oh my gosh, look at this whole being
that's coming together that's going to
be this remarkable thing." So, I think
if we just appreciate that and we say
this, this has got to be also one of the
most complex things we can imagine. Yet,
it's every day, right?
>> Whether it's, you know, a tree, you
know, from a from a acorn or whether
it's, you know, you know, a elephant
from an egg. Yeah,
>> this is every day this is happening on
Earth, right? Is is this process of
development
>> and we really didn't have much insight
into it until I'm going to say about
beginning about 40 years ago, we were
able to start to understand what was
going on. What were the chemical changes
taking place in an egg
>> that would start to shape tissues,
organs form and start to say, "Okay,
here here comes the creature."
>> [snorts]
>> This is this was a huge revolution in
biology to to understand development.
Why is development important from an
evolutionary point of view? Because it's
changes in development that give you
different kinds of creatures.
>> That's the process. If you're going to
make a creature with a longer neck or
shorter limbs or whatever, that's all
going to happen in that process of
development.
>> Yeah.
>> So, the actual process that's being
tweaked with in evolution is the process
of development. So if you want to
understand how evolution works, you got
to know how development works. That's a
decision actually I made as a young
biologist. I said okay I want to know
how evolution works. I became a
developmental biologist first.
>> Okay.
>> I wanted to understand the embryionic
>> development process. And by
understanding that what that meant was
what are all for example all the genetic
ingredients? What's what's necessary to
make a complete creature for it to all
go right?
>> Yeah.
>> Okay. just and it's as I said I I you
see this smile on my face because it is
spectacular. It's it's amazing and you
know I think a lot of people who wrestle
with evolution they're like you know it
seems
hard you know it's hard to imagine you
know how you get a from a fish to an
amphibian or something like that. Well
let me tell you it's hard to imagine how
you get from a single-sellled egg to an
adult human with 37 trillion cells.
>> Right. Yeah. I mean we basically start
off as liquids. [laughter]
Yes, exactly.
>> But we can see it. And this is the
thing. We can see it with our own eyes,
right? And we just can't see evolution
with our own eyes. It happened in the
past. It's buried in the rocks, etc.,
etc. It's kind of hard for us. It's an
incredible amount of time. Exactly.
>> But whether it's a day, a week, a month,
or nine months, we can watch development
of creatures. And now we can go in there
and we can tinker with it. We can
understand how exactly this thing
unfolds.
>> And that's a remarkable set of insights.
How do you do that in the lab? Do you
have certain species that like how to
use mice quite often? Is
>> Yeah, you know the but we have to give
credit where credit is due and and the
big
>> catalyst for understanding development
is the fruit fly.
>> The fruit it's always the fruit fly.
Yeah. Well, let me tell you the fruitly
baby paid my mortgage. Okay. So,
[laughter] that's why we got to credit
where credit's due. A fruitly what
what's the advantage of the fruitly very
short life cycle just a couple weeks or
so. uh you can keep a lot of them in a
small amount of space and they're cheap
to keep but they are complex animals
right so you start you have a little
tiny animal like that it builds all
these kind of tissues right it's got
wings it's got limbs it's got a little
heart right it's got a brain it's got
eyes so we can watch we can watch the
development of these creatures and we
can change what's happening development
>> so let me so I'm assuming it's happening
in like a a egg pupa type transition
>> egg larva pupa adult yeah
>> so are
like scanning the larvae and
>> sure we can looking at the inside
>> we can put them we can put all those
stages under microscopes and see what's
happening but what gave us power was
>> genetic approach to it. So what a
genetic approach is we deliberately
induced mutations in fruit flies and
started studying the interesting flies
that would come out. So some like one of
the most famous fruit flies was fruit
flies that instead of antenna have legs
on their head.
>> Oh jeez. Yeah,
>> that doesn't sound very useful.
>> No, but it's a it's a laboratory mutant
except for as incredibly useful as a
laboratory mutant because those are
fully formed legs in the place of
antenna.
>> And you start thinking, how do you put
legs in the place of antenna?
>> And then you map where those mutations
are and it goes to a single gene
>> and that gene turns out to be a gene
that orchestrates a big part of the
>> So let's talk process. Yeah.
>> Is it the case you blindly
ch make a genetic change, you see what
the outcome is and then you go back and
look at the genome.
>> Bingo. Exactly. And you're you're
picking those flies that are
interesting, right? You're saying, uh,
well, maybe I have a fly that changes
eye color. I go map where that happened.
But in this case, I find change a take a
fly that has legs on the top of his head
and I say, what happened?
>> So, let me let me ask you a question
there. So in in in astronomy, yeah,
>> which I know a lot more about,
>> one of the ways that uh you discover
exploding stars and moving objects like
asteroids is you do an image
subtraction. Yeah. And what you know
everything that remain the same
disappears and the only thing that
remains is what changed, right?
>> Is it like that with DNA?
>> It's logically it's very similar to
that.
>> Okay. to a geneticist, it will map the
mutation because it can it can figure
out where in the genome the change has
happened. And you can do that at sort of
a low level of resolution, sort of
chromosomal level, and say, I think it's
in this part of the chromosome. Now,
with DNA sequencing tools,
>> we can just sequence the animal and go,
there it is right there. That's the
change. The parent didn't have it.
>> Wait, that's easy for you to say, man.
When I look at images of these DNA
sequences, I just see like barcodes, you
know? I just see dots of
>> Yeah. Well, we need help with computers
to to sift through all that DNA. But
yeah, we can now pinpoint mutations just
sequencing DNA. If you take an animal
that that doesn't have the change that
has antenna in the right place
>> and the animal that has the legs on top
of its head, you can see the difference.
Bang. Okay. Couldn't do it in 1983 when
I got into the game.
>> Got it. [snorts]
>> Didn't have those tools. We we've got
those tools now.
>> So, it was a it was a longer march to to
discovery in those days. But those
discoveries, what were really important
is it taught us that there was a small
subset of genes. So the fruitfly has
maybe 14,000 genes, something like that.
There was a small subset of genes that
kind