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The Fascinating Story Of Our Mysterious Relatives, The Denisovans, With Prof. Bence Viola · The Smart Cookies podcast

0:00
And so they told me, you know, we got mitochondrial
0:03
DNA from this finger bone from Denisova cave.
0:06
They said, oh, it's from layer 11. And I was,
0:08
you know, I knew Denisovac cave and I was like,
0:09
okay, so it's probably a Neanderthal, isn't it?
0:11
And they were like, no, it's something different.
0:13
And they were like, you know, it's neither a
0:15
Neanderthal nor a modern human. It's something
0:17
completely different, which was pretty, pretty
0:20
mind blowing. We found that the last cone ancestor
0:23
of this finger bone and modern humans lived more
0:26
than a million years ago. which was in strong
0:29
contrast to the last common ancestor of Neanderthals
0:31
and modern humans, which based on the mitochondrial
0:34
DNA at the time, we calculated as between 400
0:37
,000 and 500 ,000 years ago. So this was an individual
0:41
from a group that was twice as far away from
0:43
us or twice as distant from us as Neanderthals,
0:47
which was a huge surprise. And so, you know,
0:51
this was unbelievable. And then it became even
0:54
crazier because... Bence Viola is a professor
1:02
at the University of Toronto, a paleoanthropologist
1:05
focusing on one of the most riveting features
1:07
of our prehistoric past. And that's the nature
1:11
of contacts between different hominin groups
1:13
in the late Pleistocene. Professor Viola, welcome
1:15
to the show. Yeah, thank you. It's nice to be
1:18
here. I'll have to be honest. The fact that only
1:21
some 60 ,000 years ago, a blink of an eye on
1:25
the timescale of Earth's history, really, five
1:27
different species of humans walked the planet
1:29
together at the same time. still makes my brain
1:32
want to leak out through my ears or something.
1:34
I'm just having a really hard time internalizing
1:36
this image somehow. I'm not sure if it's because
1:40
of my schooling, which happened some time ago,
1:42
to be fair, in which, with the exception of the
1:45
Neanderthals, presented this sort of like, I'm
1:47
sure you're familiar with it, classical linear
1:50
arrow of human evolution. Or it's simply because
1:54
of my species -based narcissism, you know. We're
1:57
the only ones here now because we're obviously
1:59
so exceptional and amazing. And that's how it
2:01
was meant to be. Also, I have to say, I have
2:05
the feeling when I get to think about it right
2:08
now, it's a mixture of dread, but also a tinge
2:11
of loneliness. Just to explain. The first one,
2:14
because I talk to a lot of historians on this
2:16
podcast, and even with us modern humans, usually
2:19
when we encounter other groups of modern humans,
2:22
the same species that just might look or behave
2:24
slightly differently. It's usually a horror show.
2:27
I mean, when Columbus came to the so -called
2:30
New World, the aftermath was an outright apocalypse
2:32
for the indigenous populations. On the other
2:35
hand, how cool would it be to have a Neanderthal
2:37
friend in 2026 to open a really stubborn jar
2:41
for you or something? And also a Benissavan friend
2:44
to, and here comes a big question mark, because
2:48
I have no idea what they were like. And that's
2:50
where you come in, professor, to clear the fog
2:53
of these highly mysterious. relatives of ours,
2:56
relatives we've only known about since 2008 or
3:01
2010, if I'm not mistaken. So in total, less
3:03
than 20 years. So first of all, tell me about
3:07
this discovery and about how crazy it must have
3:09
felt at the time. Yeah, I mean, you know, the
3:12
reason that you didn't learn about this in school
3:15
is that, as you said, you know, most of these
3:18
species were unknown up until very recently.
3:22
I mean, I think of the kind of the ones that
3:24
were around 60 ,000 years ago, the one discovered
3:28
first, of course, were Neanderthals in the 19th
3:30
century. But then Homo floresiensis from the
3:32
island of Flores was only discovered. The Hobbit.
3:34
Yes, the Hobbit was only published in 2004. The
3:39
Denisovans were published in 2010. I mean, Homo
3:43
luzonensis from the Philippines came out about
3:46
2015, 16, something like that. So, you know,
3:49
a lot of these groups, you had no idea that they
3:51
were around. And I think that we were almost,
3:56
I'd say, complacent in some ways. We were just
3:58
assuming that we knew what's going on. We assumed
4:02
in Eurasia, you know, things are going to be
4:04
Neanderthals or modern humans. And that was exactly
4:07
what we expected in Denisovas. So I was to kind
4:11
of to go back to 2010 or 2009 when these discoveries
4:15
were made. I was quite familiar with Denisova
4:18
Cave. I did my PhD on Neanderthals in Central
4:20
Asia. And one of the sites I studied was actually
4:23
Denisova Cave. I looked at two teeth that were
4:26
found in the 1980s that were described originally
4:30
by an American dental anthropologist, by Christy
4:33
Turner, as Neanderthals in 1986. He had like
4:37
a brief mention. He wrote about a page about
4:39
them and said, you know, these seem to be Neanderthals.
4:43
And so I studied this material and material from
4:46
nearby in the Altai, from another site called
4:48
the Kladnikov Cave and from some sites in Uzbekistan
4:52
as well. And I felt that at least the stuff from
4:56
Denisova didn't really look Neanderthal -like.
5:00
So I defended my PhD in 2009 and then went to
5:04
Leipzig to the Max Planck Institute for Evolutionary
5:06
Anthropology, which is kind of the hotbed of...
5:09
human origins research, you know, it has the
5:12
geneticists at the department at the time was
5:16
led by Svante Paabo, who, of course, later on
5:19
won the Nobel Prize for his discoveries of ancient
5:23
genomes. And also Jean -Jacques Hublin, who was
5:27
the head of the human evolution department. And
5:30
so I went there to do a postdoc and work with
5:32
both of them on the interface of genetics and
5:37
paleoanthropology. And really the day I got to
5:39
Leipzig, this was in December 2009, I had in
5:42
our new place, we had the internet installed.
5:45
And one of the first emails I got once they hooked
5:48
up the internet was from Svante from the Max
5:52
Planck saying that, you know, you're only officially
5:54
starting beginning of January, but we have some
5:56
very weird results. Can you come in and talk
5:57
to us? And so I went in and I met with him and
6:00
with Johannes Krause, who was at the time, he
6:04
was a PhD student. who was working on the Denisova
6:08
finger bone. And so they told me, you know, we
6:10
got mitochondrial DNA from this finger bone from
6:13
Denisova cave. They said, oh, it's from layer
6:16
11. And I was, you know, I knew Denisova cave
6:18
and I was like, okay, so it's probably a Neanderthal,
6:20
isn't it? And they were like, no, it's something
6:21
different. And they were like, you know, it's
6:24
neither a Neanderthal nor a modern human. It's
6:26
something completely different, which was pretty,
6:29
pretty mind blowing, especially because, you
6:33
know, once Johannes did the... phylogenetic trees
6:36
and calculated the last common ancestor between
6:40
modern humans and this finger bone that at the
6:43
time we referred to as the X woman. We found
6:46
that the last common ancestor of this finger
6:49
bone and modern humans lived more than a million
6:51
years ago, which was in strong contrast to the
6:54
last common ancestor of Neanderthals and modern
6:56
humans, which based on the mitochondrial DNA
6:59
at the time, we calculated as between 400 ,000
7:02
and 500 ,000 years ago. So this was an individual
7:05
from a group that was twice as far away from
7:08
us or twice as distant from us as Neanderthals,
7:11
which was a huge surprise. And so, you know,
7:15
this was unbelievable. And then it became even
7:18
crazier because just a few days later, we flew
7:21
to Novosibirsk to talk to our Russian colleagues
7:24
who discovered the finger bone. When we were
7:28
there, this was early January, Anatoly Derevyanko,
7:32
who was the archaeologist, who was the head of
7:37
the team in Russia, he went in his chest pocket
7:42
of his shirt when we were talking and pulled
7:43
out a tooth and showed me that tooth. And that
7:46
tooth was what we call the niece of a four. And
7:51
looking at it, it was very clear to me that,
7:53
yeah, the geneticists are right. You know, this
7:56
is neither a Neanderthal nor a modern human.
7:57
It was absolutely enormous. Like we, you know,
8:00
later on, I did the analysis and in modern humans,
8:03
there's like one in 10 ,000 modern humans who
8:05
would have a molar this big. And in Neanderthals,
8:08
it's also, there's one pathological one from
8:10
Uzbekistan, but otherwise they are all much,
8:13
much, much smaller. So, you know, it was clear
8:16
that this is something really weird. Wait, the
8:20
molar. was bigger than an average Neanderthal
8:23
molar and an average modern human molar. Yes,
8:27
like much, much, much larger. It was a Godzilla
8:29
molar. Yeah, it's so, you know, we brought it
8:33
back to Leipzig and I met with a colleague in
8:36
Leipzig who studied early Homo, so these species
8:39
that lived about 2 million years ago in East
8:42
Africa. And I showed him this tooth and I was
8:44
like, Fred, what do you think? And his opinion
8:47
was like, oh, did you find this in Ethiopia?
8:50
because he thought that this is something that,
8:53
you know, has to be from some of these earlier
8:55
species, from Homo rudolfensis or Homo habilis
8:58
or something similar. And when I told him that,
9:01
you know, no, it's 50 ,000 years old from Siberia,
9:03
he was pretty surprised. Compared to, let's say,
9:09
the Neanderthals, why have we found so few Denisovan
9:12
remains? I mean, you know, I think it's partly
9:17
historical. You know, Neanderthals lived in Europe
9:20
where... Archaeology has been done intensively
9:25
since the 19th century. There have been excavations
9:27
at sites in France, you know, starting in the
9:30
1850s and in Germany. And also Neanderthals were,
9:36
at least in some parts of Europe, were around
9:39
quite a bit. Probably that was kind of their
9:42
core area. For the Nisovans, the areas where,
9:46
you know, they were probably around a lot, places
9:50
like... probably Southeast Asia, but also large
9:53
parts of China, paleoanthropological research
9:55
started later and it was focused on different
9:59
things. I think it's mostly a question of how
10:04
intensively the research has been done. And also,
10:06
you know, it turns out that some of the, or quite
10:09
a few of the fossils we've known from East Asia,
10:12
for example, are actually Denisovans. I mean,
10:15
there was a paper just less than a week ago showing
10:19
that... teeth and cranial fragments from a site
10:23
called Xujiayao in northern China were indeed
10:26
Denisovans. And they showed this using proteomics.
10:31
They looked at the proteins in the enamel. Even
10:34
though with Xujiayao, I mean, the morphology
10:36
of the teeth, like the shape of the molars and
10:39
so on, is actually very similar to what we see
10:41
in the Denisovans cave. So we suspected this,
10:43
but it was only shown now using proteomics, convincingly.
10:49
What's the kind of... demarcation line between
10:52
one species of hominins versus the other because
10:54
these guys and gals apparently had no problem
10:57
kind of getting jiggy with it you know doing
10:58
a bit of cave tinder swiping and successfully
11:01
producing babies together so what is it that
11:05
makes us differentiate or be able to differentiate
11:09
one type of human from another is it just the
11:14
energy it's a very hard question You know, I
11:18
mean, the problem, of course, is that defining
11:21
species in general is difficult. You know, there's
11:23
like 50 different species concepts or ways that
11:27
biologists define what a species is. And the
11:30
one you learn in school usually and most people
11:33
think of the biological species concept means
11:35
that, you know, species is a group of individuals
11:38
that can breed within but do not interbreed with
11:41
individuals outside this group. And, you know,
11:44
if we take this strictly, then Neanderthals and
11:47
Denisovans and modern humans are not separate
11:50
species because they could all breed with each
11:52
other. But the problem is if you apply kind of
11:55
the same concept, for example, to polar bears
11:57
and grizzly bears, which, you know, a three -year
11:59
-old can tell apart. They look different. They
12:01
live in different climates. They behave differently.
12:04
They eat different things. But we know from genetics
12:07
that these species happily interbreed and have
12:10
interbred. There are grizzly bear populations
12:12
out there that carry about the same amount of
12:15
polar bear DNA as we carry Neanderthal DNA. So,
12:20
you know, I think the main outcome of these genetic
12:24
studies in the last 20 years is that species
12:27
boundaries are much leakier than we think. And
12:32
so I think, you know, I actually usually speak
12:35
when I talk about Denisovans, I like to call
12:37
them a population or a group because I think
12:40
calling them a species would imply to certain
12:44
or to the general public that this is something
12:47
really completely different from us, even though
12:49
in reality, as you said, you know, our ancestors
12:51
recognized them as potential mating partners.
12:54
They were similar enough that they knew that
12:57
they could reproduce, or at least they tried.
13:00
Okay, back to that Godzilla molar you mentioned
13:03
before that I can't stop thinking about. If we
13:05
juxtapose sapiens, Neanderthals, and Denisovans
13:09
sort of side by side with each other, what were
13:11
some of the key biological differences between
13:14
them? Or maybe that would be some of the things
13:16
that would immediately jump out regarding the
13:19
way they looked in terms of differences. Yeah,
13:22
I mean, you know, of course, our knowledge of
13:24
Denisovans is still quite limited because even
13:27
with the discoveries in the last 15 years, we
13:30
only have, I'd say, one cranium that's reliably
13:33
Denisovan. We have two lower jaws and then otherwise
13:36
it's mostly isolated teeth and fragments. And
13:39
we have very little with regards to post crania.
13:41
So the general body build is not very well known.
13:46
But based on the skull, It looks like they were
13:51
very large. And that also fits with there's two
13:54
bones from near Taiwan that seem to be or could
13:59
be Denisovans, a femur and a tibia, so a shin
14:02
bone and a thigh bone. And both of those are
14:05
also very large. They come from individuals that
14:07
are, you know, I always imagined them build -wise
14:09
like a rugby player or American football player,
14:12
like big muscular dudes. But also like taller
14:16
or just like more muscular or both? Probably
14:20
both. I don't think the stature was, you know,
14:23
over, you know, they were probably on the tall
14:26
end of modern humans and they were probably taller
14:28
than Neanderthals. You know, Neanderthals are
14:31
heavy, but tend to be relatively stocky, even
14:33
though, again, it's not that extreme. You know,
14:35
they are not, you know, like a male Neanderthal
14:38
would be 170, 175 centimeters, something like
14:42
that in that range, maybe a female slightly shorter.
14:45
So, you know, they are not, they're not tiny.
14:48
But the Nicevens might have been a little bit
14:50
bigger. And they also, they have very large skulls.
14:52
So the Harbin cranium, which is a skull discovered
14:55
in China, actually originally, supposedly in
14:58
the 1930s during the Japanese occupation, but
15:02
was hidden for a long time and was only published
15:04
in 2020 or 21. This Harbin cranium is the largest
15:09
hominin cranium that has ever been discovered.
15:12
It's huge. It's a really, really big guy. Also
15:17
with large brains. So one of the interesting
15:19
things, you know, people always assume that modern
15:22
humans are around because they had the largest
15:24
brains and they were the smartest. Actually,
15:26
in brain size, you know, Neanderthals are also
15:28
comparable to us. And there's actually some of
15:30
the largest brains of fossil humans that we know
15:33
are from Neanderthals. they are actually slightly,
15:39
slightly larger on average than modern humans,
15:41
even though if you correct for body mass, this
15:43
is not necessarily true anymore. But, you know,
15:46
their brain size, I would say, is at least in
15:48
the same ballpark as ours. And same with Denisovans,
15:51
like large heads and brains. And, you know, one
15:55
of the things that you probably notice is the
15:57
large brow ridges. You know, in general, these
16:00
crania are massively built, also probably coming,
16:03
you know, with strong muscles, but large brow
16:05
ridges. In Neanderthals, you have this probably
16:08
very large nose. We're not 100 % sure how the
16:12
nose of Denisovans would have looked like. I
16:15
think that needs a bit of study still. But you
16:19
probably would have been able to distinguish
16:22
the faces of these groups from each other. How
16:26
do we know that Neanderthals had large noses?
16:28
But despite the fact that we do have... a whole
16:31
skull of a Denisovan, we don't know what their
16:34
noses look like. Because noses, you know, they
16:36
just rot away. They're not bone. Yeah, yeah,
16:39
yeah. But, you know, like the parts of the nasal
16:43
aperture and the harbing cranium are not as well
16:45
preserved. You know, the upper part of the nose
16:48
and the nasal spine here at the bottom. And so
16:51
I don't think that's present. And so, you know,
16:54
people have studied Neanderthal noses for a long
16:56
time and tried to do different reconstructions.
17:00
There are just many more Neanderthal crania and
17:02
many of them well preserved. So we can have a
17:04
much better idea. I think with Harbin, we're
17:07
still a bit limited here. Okay, that's why I'm
17:12
not an anthropologist. That was a very convincing
17:14
answer. You partly gave me the answer to this
17:20
already, but I'm going to ask anyway. Let's say
17:23
you're part of like a band of Neanderthal hunters
17:27
some 70 ,000 years ago. I don't know, tracking.
17:30
some large game. And when you turn a corner,
17:32
you suddenly come face to face with a group of
17:34
Denisovans. Do you think you would immediately
17:37
know that these people are different? Or would
17:40
you think, no, they're just like us, they're
17:41
just like me, only a bit more odd looking, that's
17:44
all? That's, again, a very good question. I mean,
17:47
there's kind of two, I think two sides to the
17:50
answer of this. I mean, one of them is, you know,
17:53
we know about Neanderthals, for example, due
17:55
to... genetic data that they lived in small groups
18:00
that were quite isolated. So we have actually
18:03
DNA from 13 individuals from the cave that's
18:06
here above in my background picture. That's Chigirska
18:09
Cave in the Altai. We actually have DNA from
18:11
13 Neanderthals from this site. And what we could
18:14
show is that they were all very closely related
18:17
to each other. This is a tiny group of maybe
18:19
20 or 25 people. who rarely received input from
18:24
the outside. Maybe every few generations, somebody
18:26
came in. But in general, you know, these were
18:29
all extremely closely related. So, you know,
18:33
I'm asking myself, anyone who would have been
18:37
from outside their group would have been someone
18:39
weird, would have been someone they haven't seen.
18:43
And so, you know, yes, probably a Denisovan would
18:46
have looked different. But I don't think it would
18:49
have looked that much more different to them
18:51
than, you know, suddenly seeing a Neanderthal
18:52
from further away. I mean, you know, I think
18:55
we completely underestimate due to, you know,
18:58
our constant exposure to people of all varieties,
19:02
you know, on TV, on social media or in real life.
19:05
You know, I live in Toronto, which is probably
19:07
the diversest city in the world with people from
19:10
all around the world here. And so I see people
19:13
of every variation, you know, of every skin color.
19:16
various statures, various, you know, shapes and
19:19
sizes. And I think that, you know, a Neanderthal
19:24
that lived in a group of 20 did not have that.
19:26
Like their sole reference, like frame of reference,
19:29
was the 20 or 25 individuals that they knew.
19:33
And, you know, maybe they met with other groups
19:35
sometimes, but it can't have been too often.
19:37
Otherwise, we would see more gene flow between
19:39
these groups. Yeah, you reminded me of, I don't
19:43
know, there's some footage and I'm probably...
19:45
totally gonna butcher it on youtube of some i
19:49
don't know some french anthropologist in maybe
19:51
papua new guinea or something and he's filming
19:54
his his uh contact with some indigenous people
19:58
there and it's their first time seeing a white
20:01
person and they look like they've seen a ghost
20:04
or something they keep touching their skin and
20:06
they they're they're afraid and they're like
20:07
pointing their uh their bows and arrows at them
20:10
and um they're the same They're exactly the same
20:14
species. They only look a little bit different
20:16
and come from different areas. So it makes a
20:19
lot of sense. On the other hand, we know that
20:22
these people were interbreeding sometimes, right?
20:25
So they didn't look too weird to each other.
20:28
Actually, sometimes they looked attractive to
20:30
each other. Yeah. I mean, one of the things that's
20:35
interesting is we know, for example, in recent
20:39
humans, one of the things that's happening is...
20:42
attractiveness is in part linked to how different
20:45
you are in some genes that are linked to your
20:49
immune system, in the HLA system. So people who
20:52
are more different than you seem more attractive,
20:55
and this is mostly running through pheromones
20:57
and your sense of smell. So maybe because they
21:02
were so different, they were more attractive.
21:04
But the way I also describe it always, If you're
21:07
a Neanderthal living in a group with 20 others,
21:10
the dating pool is very shallow. You have your
21:13
cousin Bob or the ugly guy from behind a mountain.
21:18
I think it's a really straightforward choice.
21:22
My mom's going to kill me for saying this, but
21:25
on her side, the family comes from one tiny mountain
21:28
for generations and stuff with not a lot of people
21:30
around. So I think there was some of the same
21:34
stuff going on in our family for the generations.
21:37
One last name at the local cemetery and that's
21:40
it. And I felt my genes screaming for something.
21:44
Okay, I'm going to end it there. Do we know anything
21:47
about the Nisovan culture? For example, did they
21:50
use fire? What did they eat? Did they wear clothes?
21:53
Could they talk, et cetera? Yeah, I mean, you
21:57
know, again, these are difficult questions. I
21:59
mean, one of the problems is that we have few
22:03
sites where we... only have Denisovans. So, you
22:08
know, like Denisova Cave has the issue that we
22:11
have Denisovans and Neanderthals and they kind
22:13
of like occur one after the other. And so we
22:18
have a lot of different cultural, a lot of different
22:20
layers and cultural horizons, but it's not always
22:23
100 % sure who made those. You know, a stone
22:25
tool doesn't came with a label on it that says
22:28
made by, you know, Mr. Denisovan or something
22:32
else. So it can be quite difficult. And what's...
22:35
interesting in Denisova that based on the stone
22:37
tools there does not seem to be much difference
22:39
between the layers that were produced by Neanderthals
22:44
and by Denisovans. There's really very little
22:46
difference. There's some slight differences in
22:50
the fauna, in the exploitation of the animals,
22:54
but again that's less clear. But I mean the nice
22:58
thing is that we have now like new sites like
23:02
Baishiya karst cave in Tibet that is this very
23:06
high altitude Denisovan site at like 3 ,700 meters
23:09
in Xiahe province in China and there there's
23:14
only Denisovans at least up until now so we can
23:18
look a little bit at how they were hunting there
23:21
and then just a couple of weeks ago or maybe
23:26
three weeks ago some Denisovan teeth were published
23:30
from a site called Bianfu Cave in southern China,
23:33
or not really southern anyway, but I mean further
23:37
south than the other sites. And so there we actually
23:42
see quite a bit about the hunting of Denisovans,
23:47
because again we only have Denisovans there and
23:49
we have a rich record. So we see evidence for
23:52
the use of fire, we see stone tools, of course
23:54
we see We see hunting, actually relatively specialized
23:59
hunting even. So I think that we'll slowly get
24:03
a better picture of this. There should be some
24:08
differences from Neanderthals. You know, they
24:10
lived in different environments. I mean, all
24:12
these hominins clearly were able to adapt to
24:15
extremely diverse environments. I mean, Denisovans,
24:17
you have them in the Altai in southern Siberia,
24:21
which, you know, it's not Arctic, but it's a
24:23
relatively cold place. You have them in high
24:27
altitudes in Tibet. And, you know, if you're
24:31
also right, we have them in the Strait of Taiwan
24:33
between Taiwan and China, which is decidedly
24:36
subtropical. And then maybe even there's the
24:39
site of Cobra Cave in Laos, where there is a
24:43
tooth from that also seems to be a Denisovan.
24:46
which is tropical Southeast Asia. So they clearly
24:49
were present in very different climates and environments,
24:52
and they had to adapt differently to these. So
24:55
they had very plastic behaviors. And the same
24:57
is true with Neanderthals. You have Neanderthals
24:59
from the Near East, from Israel and Iraq today,
25:03
into Siberia or into Northern Germany and Poland.
25:08
And again, wherever they are, and depending on
25:11
the local environment, they hunt different things.
25:15
use different plants. They show different behaviors.
25:19
You know, we, again, Neanderthals use fire. They
25:22
don't always use it. So one of the interesting
25:24
things with Neanderthals is that there are Neanderthal
25:27
sites where there's very little use of fire.
25:29
It's not completely, I don't think it's that
25:31
they were incapable of. Maybe sometimes they
25:33
just didn't bother. They just weren't cold enough
25:37
to, you know, go through all the... all the work
25:39
of, you know, collecting firewood. And, you know,
25:43
if you don't have a lighter or matches, like
25:45
making a fire is a bit more complicated. You
25:47
can't just relight it easily every morning. So,
25:51
you know, sometimes they just couldn't be bothered.
25:54
That sounds familiar to me. Do you like cold
25:59
camping? No, I just can't be bothered with a
26:02
lot of stuff. By the way, I just presume, since
26:08
you were talking about how Neanderthals and Denisovans
26:11
had these big brains as well, that that entailed
26:14
that they used fire all the time because they
26:16
cooked food. So they spent less time digesting
26:20
processing food, which enabled them to have these
26:23
big brains. But you're telling me that's perhaps
26:24
not the case? No, I don't think that's necessary.
26:30
I mean, we know that fire does appear. relatively
26:35
early in our evolution, but it does not become
26:37
ubiquitous for a long time. I mean, you can live
26:42
on uncooked food. Well, it's a bit more difficult.
26:47
It's less efficient. But especially if you have,
26:52
and Neanderthals seem to have, and Denise and
26:54
I just don't understand enough yet about their
26:56
diet, but Neanderthals in many cases had a diet
26:59
very heavy in fats and meat and things. And so
27:03
you get enough. energy out of that again it's
27:05
you know it's tastier i think and also safer
27:08
in some ways if you cook it because you you get
27:10
rid of parasites but uh you know i mean you can
27:13
eat i don't think that having like steak tartare
27:16
or carpaccio is necessarily um less good than
27:20
a than a than a steak um or you know sushi or
27:25
whatever else right right right i meant more
27:27
like Maybe it goes back to my schooling yet again,
27:30
but they taught us that cooking food is a necessary
27:33
step for us to develop these big brains in the
27:36
first place. That's why I thought... This has
27:38
been proposed, but I don't think it's fully convincing
27:41
because... I see. It's just a theory. Because
27:43
after large brains start, you have many sites
27:48
where there's just no evidence for fire. And
27:50
of course, it can be taphonomic. Things like
27:54
ash can be washed away or charcoal. But I think
27:58
it's likely that there are just situations where
28:04
you just don't need to use fire and you can have
28:07
a big brain. You mentioned that at the new site
28:11
in China, that there was evidence of some sort
28:14
of different specialized type of hunting that
28:18
Denisovans did. Do we know any more about that?
28:24
I'd have to look at the paper again. But I think
28:28
that what they also had is that, you know, they
28:31
could show that Denisovans selected specific
28:34
individuals, you know, certain age classes of
28:36
the animals. I mean, though it is in Neanderthals,
28:40
you know, where we have lots of good data. And
28:43
I think that, you know, Neanderthals and Denisovans
28:46
are probably, you can probably see them as similar
28:50
enough that, you know, assumptions about their
28:52
behavior. Their general behavioral patterns,
28:54
I think, can be transferred. And with Neanderthals,
28:58
we see there are groups that are specialized,
29:00
you know, hunting certain animals. I mean, I've
29:03
excavated a couple of times with colleagues in
29:06
France at a site that's a reindeer hunting site.
29:09
And there's just the remains of hundreds of reindeer
29:11
there that were all killed. It seems to be a
29:14
specific season of the year when the Neanderthals
29:15
went there and hunted reindeer by this cliff
29:18
and then butchered them on site. And then came
29:21
back the next year or a few years later and did
29:23
the same thing. So, you know, they probably had
29:27
or, and again, you know, Neanderthals were around
29:30
for a long time. They were around, you know,
29:32
in a huge variety of environments. Depending
29:37
on the environment, they behave differently.
29:39
But there were certainly Neanderthal groups that
29:41
had like... mobility patterns where they moved
29:44
all through the year into different areas and
29:47
they did different things at different times
29:49
of the year. You know, when the reindeer herds
29:51
are migrating, they'd go there and they hunt
29:54
them. And, you know, maybe later on there's whatever
29:57
certain berries are in season and they'd go there
30:00
and they collect those. Or if there's, you know,
30:05
like the salmon are spawning, they probably went
30:08
there and they eat the salmon out of the rivers.
30:10
I mean, that would be. the easiest huge amounts
30:14
of biomass that you can access very easily. So
30:18
there's a lot of similarity between Neanderthals
30:21
and Denisovans. Does that mean that there's a
30:23
bigger behavioral gap between Neanderthals and
30:26
Denisovans on one side and then early humans
30:29
or sapiens on the other side? Or they also shared
30:31
some of the same behaviors and it's really hard
30:34
to tell apart? We're not that special. I think,
30:40
honestly, we're not that special after all. I
30:43
mean, we see, you know, I think one of the fascinating
30:45
things is that a lot of these behaviors that
30:48
were assumed to be something that only modern
30:51
humans did are more and more frequently. We just
30:54
figure out that Neanderthals do that as well.
30:58
You know, and it comes down to like the use of
31:00
pigments and paints and colors. you know, the
31:04
use of ornaments. For a long time, it was assumed,
31:07
you know, Neanderthals did not make ornaments.
31:09
And then, you know, we discovered that there
31:10
is this one technocomplex, the Chateau Perronian
31:13
from France, where Neanderthals seem to be making
31:16
lots of like various pendants out of animal teeth.
31:19
We have evidence from several sites that they
31:22
are using the claws and feathers of large raptors,
31:27
like eagles or something similar, also probably
31:30
as ornaments. You know, they make tools of bones.
31:34
I mean, most of these things that we assume to
31:38
be modern human only seem to be present in Neanderthals
31:42
as well. I have a one -year -old child, and one
31:45
thing that blows me away watching him grow up
31:47
is that even at this very tender age, he already
31:51
has a sense of humor. He's doing his little pranks
31:54
and then laughs at them and wants me to laugh
31:56
at them too, which I'm guessing speaks... to
31:59
the incredibly important evolutionary function
32:01
of people laughing together and bonding that
32:03
way if it happens this early, you know? In other
32:06
words, do you think that Denisovans had a sense
32:08
of humor and could crack a joke as well? Again,
32:12
you know, I think, to me, exactly as you said,
32:17
because it's such a basic thing in humans, I
32:19
would assume yes. But it's, again, it's very
32:23
hard, very hard to test. There's actually, there's
32:26
a... A couple of psychologists who looked at
32:29
Neanderthal cognition and they published a paper
32:31
about 20 years ago where they claimed that they
32:34
tried to reconstruct Neanderthal humor. And their
32:37
claim was that Neanderthals would not understand
32:39
puns or wordplay, but would be mostly like more
32:43
physical comedy, like slapstick. And it's like,
32:46
honestly, I'm sorry, this is not, it's not serious.
32:50
You cannot actually tell this. This is just.
32:54
you know, you're making this up. But I would
32:56
expect that they had some kind of humor. I mean,
33:00
you know, some of our pets can be surprisingly
33:05
mischievous, where I think, you know, they do
33:08
think that they are playing pranks on us. And
33:11
of course, you know, we probably... We look at
33:13
it from a human perspective, and so we just assume
33:16
that this is humor, even though they just do
33:19
it because they think that they'll get a treat
33:21
after or whatever, or that we find it cute. But
33:26
yes, I would expect that Neanderthals and Denisovans
33:29
also had some kind of sense of humor. But how
33:33
exactly that looked, hard to tell today, unless
33:36
we have time machines and we can go back and
33:38
watch them. Yeah, play pranks on each other in
33:42
Denisovan cave. It's going to be hard to show.
33:46
So Neanderthals were like stockier, kind of stronger
33:50
than us, as we said at the beginning. Hence my
33:53
poor joke about having a Neanderthal friend to
33:55
open a tricky jar. It's just something our minds
33:57
go to when somebody mentions Neanderthals. You
34:00
told me that Denisovans were probably much the
34:03
same that way, even bigger. Did they have any
34:06
other like defining traits? I mean, that we can
34:10
be certain of? Or am I like keep pushing you
34:13
to speculate on things that we just can't say
34:15
at this moment? I mean, you know, one of the
34:17
things that is interesting about Denisovans is
34:19
they seem to have big weird teeth. That's the
34:22
one thing that is frequent. That's one that's
34:25
relatively easy to tell. The other thing also,
34:29
in many cases, it seems like they don't have
34:32
third molars. They don't have wisdom teeth. So,
34:34
you know, in modern humans you have... two incisors,
34:37
a canine, two premolars, and then three molars.
34:40
And in Denisements, there only seem to be two
34:43
molars. And maybe these relatively large molars
34:45
that we see in them are simply in kind of, you
34:49
know, you get in two molars, you get the same
34:51
surface area as you would in three otherwise.
34:56
Maybe that's, but that is one of the things that
34:58
we find as well. Really in their body shape,
35:03
it's very hard to tell. I mean, you know, There
35:07
is one partial skeleton from China that could
35:11
also be a Denisovan potentially. So, you know,
35:14
once we have more data on that, that might be
35:17
helpful. But until then, it's just, it's very
35:21
hard. Why would they have these freakishly big
35:24
teeth? Can we surmise anything from that? No
35:29
idea. I mean, you know, people wasted about 50
35:32
years trying to figure out why certain weird
35:34
traits we see in Neanderthals are around. And
35:37
I think today most of us realize that there is
35:41
no evolutionary explanation for it. It's not
35:45
selection or anything. Sorry, can you give me
35:47
a couple of examples? What do you mean by like
35:49
weird? Yeah, for example, if you look at Neanderthal
35:51
incisors, they have what we call shovel -shaped
35:53
incisors. Their incisors are kind of curved.
35:56
They have these ridges on the inside towards
35:59
the side of your tongue. Or, you know, some of
36:02
their lower premolars have a weird shape they
36:05
have on the back of their head. They have kind
36:08
of an oval depression, which is called supra
36:10
-Aeneic fossa, which is very diagnostic for Neanderthals.
36:13
And honestly, there's no clear explanation, like
36:18
what's the point of that? And I think most scientists
36:21
today think that all of this is simply due to
36:25
random, what we call genetic drift, random effects.
36:28
Neanderthals lived in such small populations
36:31
that natural selection played a much smaller
36:34
role than... kind of random effects. You know,
36:40
having this depression on the back of your skull
36:43
was not a disadvantage. And so, you know, it
36:46
arose and it randomly just became fixed. It became
36:49
very frequent in the population. And, you know,
36:53
and people spent so much time. There's so many
36:55
papers looking at this thing and trying to figure
36:57
out why it's there. And I honestly think it's
36:59
just random. It's just, you know, there were
37:02
so few Neanderthals around that genetic drift
37:04
played a huge role. And maybe the same thing
37:07
is true for Denisovans. Who knows? So evolution
37:11
is like, if it doesn't hurt, you can keep it.
37:14
No biggie. Yeah, exactly. In many cases. You
37:19
know, I think that, you know, people think about
37:22
evolution very much in this, in the way we learn
37:25
it in school, which is completely true. But a
37:28
lot of these... Natural selection works well
37:31
when you have large populations. It works perfectly
37:34
in bacteria. You see very quickly in bacteria
37:37
that they develop things like resistance to antibiotics.
37:41
Because there's tons and tons of bacteria. But
37:45
the thing is, Neanderthals, for example, there
37:48
were very few of them. It's very hard to put
37:53
an exact number down of how many Neanderthals
37:55
were around at any given time. But I think that
37:59
we're probably looking at less than 100 ,000.
38:01
And, you know, this is in a space from like Portugal
38:04
to Siberia. It could be as low as 30 ,000 or
38:08
even 10 ,000 individuals. And so when you have
38:11
so few individuals, the likelihood of traits
38:15
being passed on really just depends on luck and
38:18
not so much on selection. Of course, you know,
38:20
if you have a Neanderthal that suddenly has only
38:22
one leg, you know, again, not a biological thing,
38:26
but, you know, or... you know, or would be unable
38:29
to see anything, you know, that would be a disadvantage
38:32
and that would be selected against. But if it's
38:35
just something weird, like, you know, slightly
38:36
weird looking teeth, it doesn't matter. It could
38:39
easily become fixed and remain around. Why were
38:46
there so few Neanderthals? in total out there.
38:50
I never heard about this before. Was it because
38:54
of what you talked about before that they were
38:55
usually forming these really tiny groups and
38:58
didn't have like genetic diversity? I mean, that's
39:02
definitely part of it. Another thing might be
39:04
simply that they, in the end, they were like
39:06
top -level carnivores, you know, like lions or
39:10
hyenas. you know, as you go up in the food chain,
39:14
you have less and less individuals of these species.
39:18
And probably the same is true for modern humans,
39:21
you know, like modern humans, the ancestors of
39:24
modern humans who were in Africa were also population
39:26
sizes. I think a million is by far the highest
39:30
that's even possible, but it's possible that
39:32
it would be much less people across all of Africa.
39:36
So this explosion in population size that we
39:41
see is something very recent. And there's genetic
39:44
methods that can look at this so -called partial
39:47
sequential Markovian coalescent analyses, PSMCAs.
39:52
You can use these to... Yeah, no, I'm not. In
39:56
the end, what you do is you kind of chop the
39:58
genome up into little pieces. the genome of many
40:01
individuals. And then for each of those little
40:03
pieces, you calculate the time of the last common
40:06
ancestor for all these individuals. And by looking
40:14
at the distribution of the ages of the common
40:16
ancestors, and this is extremely simplified,
40:18
you can kind of reconstruct the changes in population
40:22
size over time. And so we can actually see, for
40:25
example, in Neanderthals and Denisovans that
40:28
they were part of our of our population, like
40:31
the common ancestors of modern humans, Neanderthals
40:34
and Denisovans, who are relatively diverse and
40:36
large population. And then you see that Neanderthals
40:39
and Denisovans nosedive around the time when
40:41
they leave Africa. They go through a bottleneck.
40:44
And then we see the same in the modern humans
40:47
who leave Africa, you know, about 100 ,000 years
40:50
ago or so, we have the so -called out of Africa
40:51
bottleneck, which is one of the kind of strongest
40:54
effects in all genetic analyses that we look
40:57
at today. People outside of Africa have much
40:59
less genetic variability than the people who
41:01
stayed in Africa. We're just a subset of the
41:05
African genetic variability. But at least the
41:09
people who left Africa in the last about 10 ,000
41:13
years with the increasing population size also
41:15
increased their genetic variability. Neanderthals
41:18
and Denisovans never did that. What we see in
41:20
these Neanderthal and Denisovan genomes is they
41:22
go down to very, very low levels and then stay
41:25
there for a long time. indicating that, you know,
41:29
these were just very small populations. So it
41:32
means that much like the Neanderthals, Denisovan
41:36
numbers were also relatively small. I mean, you
41:40
know, the problem is, of course, the only Denisovan
41:44
genome that we have comes from Denisovan cave.
41:47
And, you know, Denisovan cave was probably, even
41:51
though we named them Denisovans, was probably
41:53
the periphery of Denisovan distribution. It's
41:56
about as far northwest as they got. I think that
42:01
probably there were many more Denisovans in like
42:04
Southeast Asia and so on, but probably they didn't
42:06
exchange much DNA with the guys up in Siberia.
42:11
You know, the distances are large and you have
42:14
huge mountain ranges in between and deserts.
42:16
And it's just hard to, even today, it's hard
42:20
to get from whatever Laos to Siberia. But if
42:24
you have to do all of this on foot, it's a little
42:27
more difficult. From the perspective of Denisovans,
42:31
what can we say for sure about the nature of
42:33
their contact with other hominins? Would they
42:37
be mainly interbreeding? Would they be killing
42:40
each other, perhaps exchanging knowledge in some
42:43
way? Or would they probably just be avoiding
42:45
each other, like you outlined with those 13 Neanderthals
42:49
that would probably be frightened even of other
42:52
Neanderthals? I mean, you know, we know that
42:57
they met. So the, you know, the clearest evidence
43:00
for contacts between Denisovans and other groups,
43:02
I mean, besides the Denisovan DNA that we see
43:05
in present -day populations, is this individual
43:08
called Denny, Denisova 11 from Denisova Cave.
43:11
The 13 -year -old girl, right? No, no, no. That's
43:15
Denisova III. That's the finger bone. Deni is
43:18
this tiny sliver of bone that had a Neanderthal
43:22
mother and a Denisovan father. So, I mean, you
43:25
know, the individual from whom this tiny sliver
43:27
of bone comes had a Neanderthal mom and a Denisovan
43:30
father. And so, you know, with this, we can show
43:33
that somewhere in the area around Denisova cave,
43:37
these two groups met and interbred. The problem
43:40
is, of course, you know, we can't really tell
43:42
whether this was this Neanderthal group into
43:46
which a Denisovan male came in and lived with
43:49
them. Or was it the other way around? Was it
43:51
the Denisovan group where a Neanderthal woman
43:53
lived and bore a child? Or was this something
43:57
completely different? You know, maybe it was,
43:59
you know, you had the weird guys living on the
44:00
other side of the mountain and kind of Romeo
44:03
and Juliet style, you know, two young kids went
44:05
out into the forest and, you know, whatever,
44:07
looking for berries and meth there. Or, you know,
44:10
it could also be something that was much darker,
44:14
you know, and something non -consensual. So we
44:16
have no idea how these things happened. But we
44:20
know that there's at least one individual there
44:22
who carried both, you know, who had a Neanderthal
44:28
and a Denisovan parent. And what's even more
44:30
interesting is that we found out that the...
44:34
father of this individual, came from a population
44:37
of Denisovans that already met Neanderthals in
44:40
the past because he had in his genome tiny little
44:43
pieces of DNA that came from Neanderthals already.
44:47
And we tried to calculate when that happened
44:49
and it happened maybe 10 to 15 ,000 years earlier.
44:54
But, you know, clearly these two groups met and
44:57
interacted. I would also assume, you know, when
45:00
they meet that there would be some kind of cultural
45:01
exchange. They might, you know, trade. They might
45:05
try to communicate, but this is very, it's very
45:09
hard to show. I mean, even in the case of modern
45:11
humans and Neanderthals, where we have much,
45:13
much more data, you know, where we have really
45:15
lots and lots of archaeological sites with lots
45:18
of material from Europe. This is something that's
45:21
been discussed very controversially for the last,
45:23
what, 40 years or so? You know, how context between
45:27
Neanderthals and modern humans looked. Because
45:29
we see European Neanderthals about... 40 ,000
45:34
years ago, seemed to show some changes in their
45:38
behavior. They suddenly have more ornaments and
45:43
art and similar things than before. And one of
45:47
the questions is, is this something they learned
45:49
from modern humans? And it doesn't seem so because
45:52
some of these ornaments actually show up before
45:54
modern humans showed up in the region. But one
45:58
of the ideas that was proposed by Nick Conard
46:02
and colleagues was that maybe Neanderthals and
46:06
modern humans, when they interacted or when they
46:10
met, this kind of motivated them to kind of make
46:16
themselves more distinct, to kind of have cultural
46:20
identifiers, wear ornaments, kind of to show
46:22
which group they come from. You know, in a way
46:27
like, you know, you have today and in popular
46:29
culture, you have you have different groups,
46:31
you have whatever the Goths who wear, you know,
46:34
black clothes and whatever to kind of signify
46:36
that they belong to this subculture. Maybe Neanderthals
46:39
did the same. You know, we wear these eagle feathers
46:41
to or these claws to show that we are this group.
46:45
And modern humans used a certain kind of paint.
46:48
I mean, hard to tell. But, you know, people always
46:51
want to kind of show that they are something
46:54
special and distinct. And maybe these contacts
46:57
led to that being more important. That's a very
47:02
funny image, like a big American high school.
47:04
You have like the jocks and Neanderthals and
47:07
you have like the nerds. Kind of sweet. By the
47:13
way, I wanted to ask the following. We don't
47:17
have a lot of Denisovan remains. And yet this
47:21
one. finger bone fragment or bone or whatever
47:24
that we do have is immediately from a person
47:27
that was half Denisovan, half Neanderthal. Wouldn't
47:29
that entail that interbreeding was much more
47:32
common than we think? I mean, yes, that's kind
47:36
of what it would. Kind of like common sense logic
47:39
that I'm applying here. Not exactly anthropologist's
47:42
gentle deduction. No, no, I mean, that's exactly
47:45
the kind of the fascinating thing that we see
47:48
is that I mean, it's the same with Neanderthals
47:51
and modern humans. I mean, we have an individual
47:53
from Romania, from a site called Oase, who has
47:56
a Neanderthal great -great -grandmother or father.
48:00
You know, it's a modern human otherwise, but
48:02
it has, like within like five or six generations,
48:04
it has a Neanderthal ancestor. And so, you know,
48:10
that would kind of indicate that this happens
48:11
all the time. But actually, if you look in modern
48:14
human DNA, it doesn't seem to be present so much.
48:17
And also, you know, if Neanderthals and Denisovans
48:19
constantly interbred, we would not see them as
48:21
genetically distinct populations, but we do.
48:24
So there are several possible explanations. I
48:27
mean, one of them might be that when this interbreeding
48:29
happens, these individuals who are hybrids, you
48:34
know, like Denny, they would have lived with
48:38
one of the parental populations and kind of bred
48:44
back to one side. So, you know, for example,
48:47
Danny would have then only, and his descendants,
48:49
would have only mixed with Neanderthals, meaning
48:53
that over time, this Denisovan contribution would
48:55
have disappeared. Another option is that there's
48:58
some kind of selection against, that actually
49:00
these hybrids were less viable. than the non
49:06
-hybrids. Maybe these, you know, in some ways
49:09
the Neanderthal and Denisovan DNA were not completely
49:11
compatible and being a hybrid or a descendant
49:14
of a hybrid was a disadvantage. We're, you know,
49:19
we're still trying to figure out these things.
49:22
But I think that there's several possible explanations
49:25
for it. It's fascinating though that we, you
49:29
know, we accidentally found an individual who's
49:32
really direct evidence for these two groups meeting.
49:35
I mean, when Vivian Sloan, who worked on this
49:40
sliver of bone on Denisova 11, when she told
49:44
me, I found it absolutely mind -blowing. I was
49:46
like, how is this possible? How can we be so
49:49
lucky that we find exactly this one piece? So
49:53
I gather from your surprise there that it was
49:56
less possible to have some sort of like a diverse
49:59
multicultural posse. comprised of a couple of
50:02
Neanderthals and a couple of Denisovans and some
50:04
homo sapiens thrown in there for good measure
50:06
that would hunt and live and chill together.
50:08
Yeah. I mean, we didn't. We didn't think so.
50:10
But, you know, maybe we're wrong. You know, maybe
50:13
it is like in the Lord of the Rings that, you
50:15
know, you have the elves and the hobbits going
50:17
out and doing good together. Maybe. Another mind
50:24
-boggling thing is the following. You keep telling
50:29
me these populations are bumping into each other.
50:32
But you also told me there were very few in numbers
50:36
living on this vast planet. How is that possible?
50:40
Like, how is it possible that these people are
50:43
even meeting in the first place? You know, like
50:45
Asia is huge. Europe is really big. Like you
50:49
said, from, I don't know, Siberia to Portugal.
50:51
And we find these populations everywhere. And
50:54
yet they keep kind of... They don't have cities
50:57
and stuff. Like what's going on there? But I
50:59
think, you know, they probably use similar resources.
51:02
You know, I think they have similar ideas of
51:04
what is the kind of environment they want to
51:07
be in. You know, and again, you know, our view
51:11
is always biased towards caves because that's
51:13
where often these remains. survive. But if you
51:18
have a large dry cave that faces south, so it's
51:21
probably warm most of the year, and it has a
51:23
really good view across the landscape, then that
51:26
would be an obvious place to live around there.
51:28
And, you know, you would not live in the swamps
51:30
down by the river. And similarly, you know, if
51:35
you follow the wandering, like the migrating
51:38
herds of animals, you know, you are kind of drawn
51:42
into the same directions. And I think finally,
51:47
you know, we have to keep in mind the immensity
51:50
of time. You know, Neanderthals were around for
51:53
300 ,000 years. And even if there were very few
51:56
people at any one time, you know, these very
51:58
few people, even if they only bump into modern
52:01
humans once they get into the same area, every
52:05
hundred years or every thousand years, that's
52:07
enough to leave genetic traces. Same with Neanderthals
52:10
and Denisovans. As a pin anthropologist, one
52:17
of the things you really have to wrap your head
52:19
around is how immense the time spans are that
52:23
we talk about here. The accuracy of our dating
52:28
methods are very limited as we go back. C14 dates
52:33
are probably the most accurate, but if you go
52:35
back close to 50 ,000 years, you probably have
52:38
a 2 ,000 or 3 ,000 year inaccuracy in your C14
52:43
dates. And, you know, if you have two individuals
52:46
that to you seem contemporary, but are 2000 years
52:49
apart, you know, that's a bit of an issue. It's
52:51
like, you know, me and Julius Caesar, it's we're
52:53
contemporaries, but it's not like we're hanging
52:56
out on the weekends. That's a very good comparison.
52:59
Also, yeah, I had some Roman historians on the
53:01
podcast. You would probably wouldn't want to
53:03
chill with that guy. Generally speaking, and
53:09
correct me if I'm wrong here, but modern Asians.
53:13
have more Denisovan and Neanderthal DNA than,
53:16
let's say, Europeans or people from Sub -Saharan
53:18
Africa, right? Does that add any sort of like
53:23
piece to the mosaic of this story of the Denisovans?
53:27
Yeah, I mean, so in general, the Neanderthal
53:32
ancestry is pretty similar in Europeans, Asians,
53:36
and everyone outside of Africa has roughly the
53:38
same amount of Neanderthal ancestry. Asians have
53:41
maybe a tiny bit more, but it's... It's not 100
53:44
% clear. It's pretty clear that everyone has
53:47
more than African populations. And that's simply
53:50
because, you know, our ancestors met Neanderthals
53:53
once they left Africa. And there has been some
53:55
back migration into Africa that carried back
53:58
a little bit of Neanderthal DNA. But those are
54:00
only small amounts. Now, the Nisovan ancestry
54:04
is something we don't see in Europe at all. And
54:07
Asian populations have a bit, like 0 .1, 0 .2%.
54:12
as compared to 1 % to 1 .5 % of Neanderthal DNA,
54:15
so significantly less than Neanderthal DNA. What's
54:18
really interesting, though, is that you have
54:19
indigenous groups in the Philippines, for example,
54:22
who have very large amounts of Denisovan DNA,
54:26
maybe around 5 % or so, so several times what
54:29
they have of Neanderthals. And similarly, populations
54:32
in Papua New Guinea. And Australian Aborigines,
54:35
so Melanesian groups, also have relatively high
54:38
amounts of Denisovan ancestry, much more than
54:41
Neanderthal, again, 3 % to 5%. So, you know,
54:45
it seems to be present in these different populations.
54:47
And the big question is, what does it actually
54:51
mean? You know, what does it mean to have whatever
54:53
1 % of Neanderthal DNA or 0 .1 % of Denisovan
54:57
DNA? Is that something that we should just ignore?
55:00
Because, you know, it's like thousands of our
55:01
genome. Who cares? And so there's a lot of really
55:04
interesting research looking into the effects
55:07
of these, what we call archaically introgressed
55:10
segments. So portions of Neanderthal and Denisovan
55:12
DNA in our genomes and what they actually do.
55:16
And so probably the most fascinating one of these
55:19
is with regards to Denisovan ancestry in Tibet.
55:25
So Tibetan populations today, you know, live
55:27
at high altitudes. In general, if you look at
55:32
Tibetans, they are genetically quite similar
55:34
to Han Chinese. And so across their whole genome,
55:38
you have about 0 .1 % of Denisovan DNA. And that
55:41
means that there's like tiny little chunks in
55:44
their genome, more or less randomly distributed.
55:47
And if you compare two or three individuals,
55:49
they don't have exactly the same Denisovan genomes.
55:52
They're all different Denisovan fragments. They're
55:55
all different little pieces of Denisovan DNA
55:57
floating around in their genomes. But because
56:01
Tibetans live at high altitudes, they had to
56:03
adapt to this. At high altitudes, you have a
56:06
lack of oxygen. And there's especially one gene,
56:09
IPES1, which is a hypoxia pathway gene. It's
56:13
a gene that helps people to deal better with
56:17
low amounts of oxygen. And especially what we
56:20
found is there's one variant of this gene. This
56:23
is work by Emilia Huerta Sanchez and her colleagues.
56:29
they found that there's one genetic variant in
56:33
Tibetans that leads to women having larger babies.
56:39
Like the birth weight of these babies is larger
56:41
by whatever, 100 grams or so, which you think
56:44
like, oh, that's bad. It's harder, bigger baby,
56:47
harder to give birth. But large babies are a
56:50
very good predictor of infant survival. Larger
56:52
babies are much more likely to survive. And this
56:56
is because, you know, these babies just get more
56:58
blood and oxygen while they're developing in
57:00
the womb. Now, the fascinating thing is if you
57:03
look at this genetic variant that's responsible
57:06
for this haplotype, the variant you see in Tibetans
57:11
is not present in any other modern human population.
57:14
It's actually very far away. Like most modern
57:16
human populations have, you know, variants that
57:19
are like close together. There's like one or
57:21
two or three differences between them. This one
57:25
is like 40 differences, like 40 changes from
57:28
the closest modern human variant. But surprisingly,
57:32
the variant we see in the Denisovan genome is
57:35
very close to it. So this is very similar to
57:38
the variant seen in Denisovans. And so the idea
57:41
is that the ancestors of Tibetans picked up this
57:45
genetic variant or something similar to it from
57:48
Denisovans. And in the beginning, while they
57:52
were at low altitudes, this was at a frequency
57:54
of 0 .1%, because it was kind of randomly distributed
57:57
in their genome. But today, it's present in 80
58:01
% of Tibetans. So it's been selected for extremely
58:03
strongly. As they move to high altitudes, suddenly,
58:06
you know, having bigger babies, despite the lack
58:08
of oxygen, was a huge advantage. And so this
58:12
was published in 2014 or 15, I think. And so
58:16
based on this, the authors predicted maybe Denisovans
58:18
were adapted to high altitudes. And at this time,
58:21
the only Denisovans we had were from Denisovak
58:23
Cave. And Denisovak Cave is 750 meters above
58:27
sea level, so it's not a high altitude site.
58:30
But then in 2020, this mandible from Baishiya
58:34
Karst Cave in Tibet came out from 3 ,700 meters
58:38
altitude, showing that yes, Denisovans were actually
58:41
there at really high altitudes. And up until
58:45
then, the assumption was that nobody lived at
58:48
these high altitudes until maybe like 20 ,000
58:50
years ago. And this mandible is whatever, 180
58:53
,000, 160 ,000 years old. So much, much older
58:56
than we thought. And again, it's proof that the
58:59
Nismans could also deal with these high altitudes.
59:03
And this is what made it possible for present
59:05
-day Tibetans to also live up there, which is
59:08
really cool. That is fascinating. What we can
59:13
say for certain is, besides their freakishly
59:16
big teeth, they also had mega -chonker babies.
59:20
Probably. What can you tell us about the demise
59:25
of the Nusavans? Again, I'm probably going to
59:29
have to twist your arms to speculate away, but
59:36
you must have some hypothesis about what happened.
59:41
Actually, not really. I mean, you know, we have
59:45
no idea what happened. I mean, you know, I would
59:48
assume that it probably was also linked to climatic
59:51
events that happened around that time. I mean,
59:54
you know, we assume that Nice has probably also
59:56
disappeared somewhere between 50 and 30 ,000
59:59
years ago, but we can't be 100 % sure. This is
1:00:02
the time when modern humans show up in East Asia
1:00:06
and Southeast Asia, in Northern Asia as well,
1:00:09
like the earliest. fossil from northern asia
1:00:11
from siberia is about 45 000 years old from china
1:00:15
the earliest modern human is also in the range
1:00:18
of maybe a bit over 40 000 southeast asia there's
1:00:22
actually slightly older maybe even 50 or 55 000
1:00:25
years old modern humans um you know one one possibility
1:00:30
would be that the modern humans just came in
1:00:32
with large populations there were just more of
1:00:34
them and so the denisovans were either out -competed
1:00:39
or just were mixed into these, you know, modern
1:00:42
human population. And they became part of it.
1:00:45
And as they just bred with modern humans from
1:00:48
then on slowly, the Denisovan contribution became
1:00:51
less and less. But in reality, of course, we
1:00:54
don't know. I mean, there are some really weird
1:00:56
results. There's a couple of studies looking
1:00:59
at the genetics of top ones that found... very,
1:01:04
very late introgression. So very late interbreeding
1:01:07
with Denisovans, maybe in the range of 20 ,000
1:01:10
years, which to me is rather mind -boggling because
1:01:14
20 ,000 years ago, the ancestors of Papuans were
1:01:17
already in Papua New Guinea. So this would mean
1:01:20
that Denisovans would have been there as well.
1:01:22
And there's absolutely no archaeological evidence
1:01:24
for that up until now. So, you know, hard to
1:01:29
tell. But a very interesting question. And, you
1:01:34
know, of course, that's also the people who migrated
1:01:36
to Papua New Guinea kind of had to move through
1:01:39
Flores and potentially would have met there also
1:01:43
the last Homo floresiensis, the last hobbits.
1:01:48
I'm very curious how the interactions would have
1:01:50
looked and whether there were any. But without
1:01:55
DNA, it's going to be very hard to tell. So given
1:02:00
what we've discussed, at the very beginning of
1:02:03
this conversation, I guess that it's completely
1:02:05
within reason to expect that there might be even
1:02:07
more undiscovered species of humans out there,
1:02:10
right? Or of ancestors or relatives whose remains
1:02:12
we just simply haven't stumbled on yet. Yes,
1:02:16
I think, you know, I think that's pretty clear.
1:02:21
You know, we've, in the last few years, I mean,
1:02:24
we just had, even if we just look at the stuff
1:02:26
that's very recent, you know, we had... Floresiensis
1:02:30
on Flores, Lusonensis in the Philippines. We
1:02:32
have Denisovans. We have Homo naledi in South
1:02:35
Africa, you know, dating to 300 ,000 years ago.
1:02:38
There's just lots of stuff. It's possible that
1:02:40
in Africa, we actually have more than one species.
1:02:43
You know, the fossil record outside of East and
1:02:47
South Africa is very limited. And so, you know,
1:02:51
who knows what was going on in West Africa? Were
1:02:54
there hominins there? It's likely, but... but
1:02:59
we don't know who they are. And the problem is,
1:03:01
you know, using only morphology, it's going to
1:03:04
be always very hard to show these things like
1:03:07
gene flow. There are some people who work on
1:03:10
this. Becky Ackerman from Cape Town has published
1:03:13
a series of papers looking at kind of morphological
1:03:17
indicators of interbreeding. So maybe using some
1:03:22
of those methods, we can figure out something,
1:03:25
but otherwise we just have to wait for... technology
1:03:27
to advance and for some fossils to show up that
1:03:30
actually preserve DNA that allow us to look at
1:03:33
these questions. Professor, what's mind -boggling
1:03:40
to me is that we're still here. All of these
1:03:43
groups have died out and yet we're still here
1:03:45
and we're just as susceptible to climate shocks.
1:03:48
I don't know if this is true, but I read somewhere
1:03:51
that at a certain point there was like a thousand
1:03:53
or two thousand or a couple of thousand humans
1:03:55
left. on Earth. We almost died out as well. But
1:04:00
it didn't happen. Is it pure chance? Is it that
1:04:03
we are a little bit exceptional at the end, nevertheless?
1:04:07
Or is it something else that we've missed during
1:04:10
this conversation? No, I mean, chance definitely
1:04:16
plays a role in it. I mean, we know that there
1:04:19
were modern human populations that disappeared.
1:04:24
we have this individual from Ustishim, from Siberia,
1:04:29
this 45 ,000 -year -old modern human. We have
1:04:32
a complete genome from this individual. And what's
1:04:37
fascinating is that this individual has no living
1:04:39
descendants. So this is a population that colonized
1:04:41
Northern Asia 45 ,000 years ago, but then just
1:04:45
completely disappeared. Same with some of the
1:04:48
fossils we have from Europe. Some of the earliest
1:04:51
modern humans in Europe are not related to any
1:04:54
later populations. These were groups that likely
1:04:57
colonized these areas. And then due to most likely,
1:05:01
you know, changes in the climate and in the environment
1:05:06
disappeared. You know, Siberia is a relatively
1:05:09
marginal environment, even during warm periods.
1:05:12
And if it suddenly gets much colder, you're pretty
1:05:14
screwed if you're up in... in central Siberia
1:05:17
where Ustashim is. At the same time, one of the
1:05:22
fascinating things we see in almost all of these
1:05:26
modern humans is that they are genetically much
1:05:29
more variable than Neanderthals or Denisovans.
1:05:32
They seem to have some kind of mechanisms to
1:05:36
keep the genetic variability high. And these
1:05:40
must be something cultural. I don't know whether
1:05:43
these would be groups that meet up once a year
1:05:47
or from time to time to exchange individuals.
1:05:50
But there seem to be some mechanisms around that
1:05:53
reduce this inbreeding that we see in Neanderthals
1:05:56
and Denisovans. I mean, Neanderthals in some
1:05:59
populations, at least, and the ones that we know
1:06:01
genetically best in the Altai, this is... I mean,
1:06:05
we have a Neanderthal from Denisova Cave that
1:06:07
has parents that are either like half siblings
1:06:11
or like grandparent, grandchild or like uncle,
1:06:15
niece, aunt, nephew, something like this. Extremely
1:06:19
closely related. And that's probably because
1:06:23
there just, you know, weren't other people around.
1:06:27
As I said, you know, very, very shallow dating
1:06:29
pool. And so modern humans seem to have had some
1:06:35
mechanism to counteract this. And I assume that's
1:06:38
something cultural, but we don't understand it
1:06:41
sufficiently yet, I think. So maybe it all comes
1:06:45
down to what we were talking about there in the
1:06:48
middle about how people who look very different
1:06:51
to us look very appealing to us. Maybe we just
1:06:54
have more of that. Also, did we form bigger groups
1:07:00
then? than Neanderthals or Denisovans? Is that
1:07:03
fair to say? I don't think like that. Is that
1:07:07
a cliche as well? Yeah, I think that's a bit
1:07:10
of a cliche. I mean, you know, and again, like
1:07:12
reconstructing group size is extremely difficult
1:07:15
in the past. But it seems to be generally, you
1:07:19
know, more environmentally determined in hunter
1:07:22
-gatherers, for example. I think it depends a
1:07:24
little bit on how productive the environment
1:07:25
is, how large the groups are. And I would assume
1:07:29
the same with Neanderthals and Denisovans, that
1:07:31
in environments where, you know, you have lots
1:07:33
and lots of food, lots of raw materials and resources,
1:07:37
you'd have larger groups. And in areas that are
1:07:40
more marginal, you'd have smaller groups. I don't
1:07:44
think that's necessarily a modern human Neanderthal
1:07:48
-Denisovan difference. But again, it's very hard
1:07:52
to study. Right. Yet another kind of... stereotype
1:07:56
I had in mind. I thought this was our superpower,
1:07:59
that we could form larger groups. We were always
1:08:02
taught that, that we're not the strongest, we're
1:08:04
not the fastest, we're not the biggest, but we
1:08:06
can form these bigger groups and bigger tribes
1:08:09
and bands that Neanderthals and probably Denisovans
1:08:13
couldn't. But you're telling me we're... Maybe
1:08:15
these contexts were exactly that, that you have
1:08:19
these small groups of 20, 25, 30, maybe 50 individuals,
1:08:22
but because they come together, every few years
1:08:26
into a group of 500 where they can then exchange
1:08:29
individuals and does also genetics, you know,
1:08:34
that would in some ways mean that you have this
1:08:38
larger kind of virtual group. It's not like the
1:08:41
permanent group, the people you're constantly
1:08:43
with is just a small, but you have these larger
1:08:47
social networks. I do think that these, you know,
1:08:49
these larger social networks definitely helped.
1:08:53
A bit of a wild question at the end, Professor.
1:08:55
If AI does become sentient, like many experts
1:08:58
believe, including some I hosted on this show,
1:09:01
thus making us obsolete, will we be the Denisovans
1:09:04
of tomorrow? What do you think? I bet you weren't
1:09:09
expecting that. I hope not. But, you know, who
1:09:14
knows? I am a little bit worried. Mostly about
1:09:20
the social effects of what could happen if lots
1:09:24
and lots of people lose their jobs and get replaced
1:09:27
by AI. That's going to be a very, very ugly thing.
1:09:32
And so I'm not so much worried that there's machines
1:09:36
coming after us, but more that people just get
1:09:39
very, very mad. And that's bad. People do horrible
1:09:44
things to other people when they're mad. that
1:09:48
could lead to very serious problems. I'd like
1:09:52
to avoid that. A very reasonable take, Professor.
1:09:56
Thank you so much. This was a very, very interesting
1:09:58
conversation. I really enjoyed every second of
1:10:01
it. Where can people follow your work? I guess
1:10:03
you're too busy to have social media. Yes, I
1:10:06
mean, I have some social media, but I don't really
1:10:08
use it for scientific outreach. I try to, you
1:10:12
know, I try to go and talk to podcasts or...
1:10:16
or journalists, I'm always happy to talk about
1:10:19
my work, but I'm just not big on the social media
1:10:22
thing. All right, cool. I really hope we get
1:10:25
to do this again with more exciting findings
1:10:28
on the Denisovans. Thanks again. Thank you. An
1:10:31
absolute pleasure. Yeah, I really enjoyed it
1:10:34
too. Thank you so much for listening. Please
1:10:35
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It really helps, but you know what would help?
1:10:42
even more if you'd consider supporting me on
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patreon or becoming a member on youtube that
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way you're going to get all episodes early they're
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going to be ad free and there's also going to
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be bonus ones available only there yes yes also
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smaller truly independent creator it feels good
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it feels nice you know who else feels nice my
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existing patrons of course the absolute legends
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kings and queens doing the lord's work out there
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seriously peeps without your support i would
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have given up a long time ago, and you should
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know that. So my eternal gratitude goes to Philip
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Boyd Turner, Long, Jan Podgornik, Barbara Dusak,
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Tržan, Saša Viputnik, I'm deeply touched as always.
1:11:52
Thanks again.