- Greetings everyone,
my name is Jassim Al-Oboudi. I am a PhD student
here at UW-Madison and chair of our
Darwin Day events. Welcome to all of our
in-person and online attendees for tonight's session
of Wednesday Nite @ the Lab, which has partnered
with Wisconsin Evolution for this special
Darwin Day seminar, celebrating the
enduring contributions of one of biology's
most prominent thinkers. And I, of course, by that,
mean John Hawks. [attendees chuckling] Now, technically, Darwin's
birthday is this Sunday, February 12th,
but we just couldn't wait to start celebrating, and I hope
that some of our events might prompt some of you
to have your own little Darwin Day
celebrations this weekend. I want to briefly note
that we have another excellent speaker
lined up tomorrow, earlier in the day. And on Friday, we have
a community celebration with some free food
and science outreach activities for kids, which will
culminate in an art exhibition which features participants of our Darwin Day 2023
art competition. More details can be found at
evolution.wisc.edu/darwin-day. I would also like
to acknowledge support for our Darwin Day events from the College of
Agricultural and Life Sciences, the College
of Letters and Sciences, the Nelson Institute
for Environmental Studies, and the Graduate School
of UW-Madison. Now for the event at hand. It is a real privilege for me
today to introduce John Hawks. He is the Vilas-Borghesi
Distinguished
Achievement Professor in the Department of
Anthropology here at UW-Madison, a department he joined as an
assistant professor in 2002. John engages in diverse
science outreach, including an active
social media presence, a personal website detailing
scientific advances, and contributions to popular
books and lecture series on evolutionary biology. He's also conducted
extensive work on human evolution,
participating in projects that range from the origin
of early humans all the way up to the last 10,000 years
of our history as a species. This includes extensive
field work in Africa, Asia, and Europe, analyzing
archeological specimens and conducting complex analyses
on genomic data from humans. Notably, John has
extensive collaborations with members of the
University of Witwatersrand in South Africa, with which
he has made important and compelling contributions to our understanding
of human evolution. But you are not here to hear me. You are here to listen
to the expert. So without much more ado,
and I appreciate your patience with me, please join me in
welcoming Professor John Hawks. [attendees applauding] - That's great;
thank you so much. All righty, thank you everybody. I am so excited
to be here tonight. You know, it's been a long
time since I was here, and I'm gonna give you
some updates on what we've been up to. We have exciting things going on
in the field in South Africa. I'm gonna focus tonight
on the bigger picture. How do discoveries about the
behavior of ancient hominins, who are very diverse, how
do they inform our knowledge of ourselves and our connections with those other
ancient hominins that existed in the past? We are truly encountering minds
that are different from our own, minds that may be shared
from common ancestors with us, and finding evidence of them is telling us about what
those ancestors were like, but also minds that have
undergone their own adaptive and evolutionary processes,
minds that have become different from ours in intricate
and interesting ways. I'm gonna start, as I often do,
by taking you into the field. Since I was here last, we've
had a number of discoveries in the Rising Star cave system
of South Africa. This one was in the news
about a year ago, the discovery of a skull
of a child Homo naledi individual
that we named Ledi. The Rising Star cave system is underneath this
really wonderful, sort of lovely,
natural area now, and if we go underground
as I was this last summer, we find a complex cave system with more than three kilometers
of mapped passageways. I wanna take you
virtually underground. This is a part
of the cave system. We're now flying past
the Dragon's Back and into the Dragon's Back
Chamber. And you're gonna
hear a good amount about that in a little bit. The narrow passage
that you see there is the Superman's Crawl,
and as you emerge from it into a larger chamber,
you have to turn and climb, and that climb takes you
through tortuous passageways that involve a couple of ladders
and some pretty narrow squeezes until you reach the upper parts
of the cave system and the main entrance
of the cave that we're flying past now. This is just a small part
of the cave system. It is a beautiful
underground space. It's intricate
in its passageways, and it is challenging for our team to go through
in many places. There are parts
of the cave system that are incredibly difficult
to pass through that I cannot enter, that I
have incredible colleagues and collaborators
who have the skills and are able to do it,
and it's an amazing experience to be able to be there
and be part of the research. As I've, probably
you've heard before, the Homo naledi discovery began
in a part of the cave system that we today call
the Dinaledi Chamber at the far left of this image. That chamber is connected
to the rest of the cave system through a very narrow
vertical passageway that we call the Chute. That vertical passageway is
about a 40-foot climb down into the Dinaledi subsystem
of the cave, as we call it now,
and it has a minimum width of about
seven and a half inches. It is a very challenging climb
based on size, and so it takes very specialized
skills to enter this. When Steve Tucker and
Rick Hunter entered that space for the first time in 2013,
they discovered bones on the floor of the chamber. Lee Berger, my collaborator at the University
of Witwatersrand and National Geographic and I have described all of this
in our book<i> Almost Human.</i> This is old news at this point, and so I'm gonna
talk about new news. But let me set the context. After we discovered this
enormous array of bones, more than 2,500 fossil fragments
of Homo naledi to date that we've uncovered and
excavated from the cave system, as we uncovered this,
we faced a number of interesting discoveries and a number of challenges
of interpretation. Homo naledi was very similar
to us in some important ways. They were upright walking. They walked bipedally,
like we do. Their legs were relatively long
for their body size, and so we think that they were
efficient long-distance walkers. They were relatively skinny. They stood about the height of very small-bodied human
populations today, something like 4' 6" to 5' 2"
in females and males. Their body mass was
approximately 40 to 50 kilograms, so something like
80 to 120 pounds, so they're small-bodied human
in size. They're walking like us,
but they have adaptations in their shoulders and their
hands that indicate to us that they were probably
much more efficient climbers than humans are today. Their hands, however,
have morphologies that are specialized in the
wrist, in the fingertips, and in the sort of
flexibility of the fingers, the length of the thumb
in particular, that are associated in humans
and Neanderthals with stone tool manufacture. And so we think that they
were competent tool makers in addition to being
very good climbers. There were many differences
between their skeleton and ours that set them closer to some
earlier relatives of ours, relatives like Australopithecus. In particular, the size
of their brains was about a third the size of the
average human brains today. Their range about
450 milliliters to about 600 milliliters. That's the size
of very early hominins and very different
from today's humans. So this species was
really different from us in really interesting ways. We discovered over the course
of a couple of years of work that the time that these
hominins were deposited in this cave system was between
241,000 and 335,000 years ago. So this species existed
at around the same time as our own species was
first coming into existence in the range of about
200,000 to 300,000 years. That made them much more recent
than the very early hominins that they resemble
in some details. Australopithecus lived
in this part of South Africa before about two million years
ago. So this species is here
at the same time as our immediate ancestors, and that posed a number
of challenges. What were they doing there
and how did they potentially coexist with other
species, including our own? In 2017, we announced the
discovery of a second chamber in the cave system,
the Lesedi Chamber, that included this
amazing skeleton, the Neo skeleton,
as we named it, and a number of other
fossil discoveries. This second chamber highlighted
to us that this species was not just an
accidental occurrence in one remote chamber. This was a species that was
actually using substantial parts of this underground space, space that has not changed
in its depth or in its difficulty to reach in the most distant parts
of the cave since Homo naledi
was using the cave system. Since I talked with you last,
we had some of the Homo naledi fossils
here in the United States. In Dallas at the Perot Museum
of Nature and Science, our team helped
assemble an exhibition of Homo naledi material that
included the reconstruction of this beautiful
skeleton reconstruction by an artist of Neo,
so you get an idea of what Homo naledi looked like
from a distance. And I think that
in skeletal terms, this is a pretty good
reconstruction. Since I talked
with you last here at Wednesday Nite @ the Lab,
we also have done a really amazing amount
of work in visualization and understanding the scope
of the cave system. I wanna take you
on a virtual reality tour of the Dinaledi subsystem
of the cave. You're now entering via the
Chute into the part of the cave that we call the
Hill Antechamber. You can see on the floor here
right in front of us the excavation area that
I'm gonna talk about in a moment, where we uncovered
a block of fossil material of Homo naledi that
is really astounding. We're flying over
the excavation area and now down a steep slope
further into the subsystem, where we arrive at a choice
of two passageways. And we're about to enter
into the left-hand one and squeeze along another
about five meters through this very narrow
passageway into the Dinaledi chamber
itself. That chamber is a special space. It's a place where Homo naledi
existed at one time, where we've found more bones
of them than we've found of any other hominin
except for Neanderthals in an assemblage this large. It's a remarkable space,
and the floor area of this still contains abundant
fossil material. You can see here an area that
we had been excavating in 2018, and that remains there
on the floor of the chamber as we study it and try to
understand its arrangement and what it represents. The Letimela discovery
came from further yet. If you go past the
Dinaledi Chamber, you enter into an intricate
series of fissures that, as you'll see Steve Tucker
here moving through them, are incredibly narrow. You're gonna hear the word
incredibly narrow from me a lot tonight,
because that's a theme in this cave system. Here you'll see Steve taking
off his helmet so that he can squeeze through this
place that's too small for his helmet to pass. And continue on. You'll see the light
there past him. It's about three meters distant. And if we go further on,
Steve has the video now and he's recording Marina
Elliott, who is excavating in this situation
in a remote fissure passage that's about 10 meters further
than the Dinaledi Chamber, where on the floor surface
were bones of Homo naledi. We are finding bones of naledi in incredibly difficult
to reach places, in places that are rather
difficult for us to understand in terms of how the bones
reached this place, what the behavioral interactions
were that were leading naledi
to be in some of these spaces. They're remarkable,
and they're a big challenge for us to understand. Here, where Marina was working, was where the
Letimela skull was. We now have discoveries
of naledi bones from more than seven localities
throughout the cave system. This is an amazing array
of evidence of the behavior
of this fossil species. We are working to understand
that now. One hypothesis that we're
working with is the hypothesis that naledi was using these
spaces for mortuary practices, that there was something special
about their interaction with these deepest parts
of the cave system. For naledi to be so familiar
with some of these very remote spaces
indicates to us that they must have been
using the cave system in its more easy to reach
surface areas really quite a lot. And so you know, they must
have been living there and they must have been
carrying on ordinary activities in some parts of the cave system for them to be
familiar enough with it to move into these very deep
parts of the cave system where they apparently carried
out different activities, special activities. Why do I say special? Because ordinarily,
when we find hominin remains inside of caves where the
hominins are hanging out, we find abundant evidence
of their lives. We find the stone tools and
the refuse of tool manufacture. We find the bones of animals
that they were interacting with. We find evidence
of their behaviors other than their bones. In this context so far,
we're finding evidence of naledi remains, including
articulated parts of skeletons. So we have set out during
the past several years to investigate more broadly
the utilization of the cave system to try
to understand the behavior of this ancient species. We are working to understand
a cultural pattern of activity, and we're doing it by probing,
exploring, and excavating in spaces where we have
no evidence previously. Here you'll see
Maropeng Ramalepa, one of our exploration team
working in the Hill Antechamber. He's digging right here
on a shelf of flow stone right at the base of the Chute
as you enter into the chamber. This is Becca Peixotto working very near where you
just saw Maropeng, and she's working on
a ladder beneath her on the Hill Antechamber floor. I told you that there
was an excavation area. This is what she's working on. And in 2017, our team
exposed a massive assemblage of naledi fossil material
that we documented and put inside a plaster jacket,
like a dinosaur bone, and brought it out of the Chute. This was a major accomplishment, and the team had to have
enormous teamwork to do this. We have, since that time
in the spring of 2018, been studying the contents
of this block. And the contents of the block
are nothing short of amazing. You can see abundant skeletal
and dental material in this. There's evidence from many parts
of the body of at least two individuals. It's a remarkable array of bone. We're studying it
with techniques that have never
been applied before, including right now, this block
is in Grenoble, France, where it is undergoing synchrotron-aided
micro CT scanning, which gives us a scan
of the inside of this thing at nano,
at micrometer resolution. So it is going to be A,
an enormous amount of data, I gotta tell you, but B,
it's going to be one of the most detailed
documentations of a fossil assemblage
of hominins that's ever been uncovered. Unfortunately, that
kind of work takes time, and so as that develops,
we're continuing to work by exploring and excavating in other parts
of the cave system. The Dinaledi Chamber, which
you reach through the Chute, is adjacent to a massive block
called the Dragon's Back, which is a narrow ridge
of rock that extends to a maximum height of about
12 meters or about 40 feet, which you climb to get to the
area where you can access the Dinaledi subsystem
of the cave. That Dragon's Back
is our access point to the Dinaledi subsystem. We think that it was also
Homo naledi's access point, and our work in geology
and in excavation is targeted toward understanding
what the interaction of naledi with this area
might have been. This last year in 2022,
we began an excavation in the Dragon's Back Chamber. It's logical that if
Homo naledi was accessing the deeper parts of the cave through the Dragon's Back
Chamber, that indeed we might
find evidence of Homo naledi's activity in
the Dragon's Back Chamber also. But we had never
excavated there. It was a passageway for us,
but we hadn't dug to see what was
underneath the surface. I will say, we had some
pretty good reasons to think that there might
be something interesting under the surface. There are brecciated fossils
that are in the ceilings and some low overhangs
within this chamber that include bones that
look like Homo naledi bones. And so this is a
pretty promising place to look for fossils. And in 2022, our team
assembled in July and August and began working in the
Dragon's Back Chamber. You see here the team
getting going, including on the right here,
Sarah Johnson, who's here in the crowd, our graduate,
one of our graduate students here at the University
of Wisconsin. Yeah, give her a round
of applause please. [attendees applauding] You gotta understand,
she is sitting here listening to me say, "This is an
incredibly challenging climb, this is so difficult." And when Sarah came out of the
cave having done this climb, she says, "I don't see
what's so hard about that." [audience chuckling] Now, there's some
difference in dimensions [audience chuckling] between me and her
that make this somehow a different kind
of physical challenge. And I will say that it's
not only about body size. It's also about climbing skill;
it's also about body awareness. And Sarah is a climber
and she's really good at it. So having her join
this expedition to work in Dragon's Back
was really amazing. The Dragon's Back excavation
season this year was supervised by Dr. Keneiloe Molopyane,
who is our team member and collaborator at the
University of Witwatersrand and included two of our
graduate students here from the University
of Wisconsin, Sarah and Erica Noble. So this was an amazing
get back into the field and get back into Rising Star
kind of field season, and it was rewarded with some
amazing discoveries. You see the team here working
in the Dragon's Back Chamber, Keneiloe here in the front, behind her Erica Noble,
then Ginika Ramsawak, and then Sarah there
furthest in the back, and we were maxing out the cave,
right? This is about as much excavation
as we could possibly do in this area,
sampling different parts of this area of the cave system. And in this area
of the cave system, beneath the surface,
we found abundant evidence of charcoal and fire. This is a first for us
in the cave system. And Lee Berger, my friend,
announced it to the world last fall. As we're exploring in this
cave system and beginning to understand that this
is not just a fossil space, it's actually a cultural space,
it becomes really important for us to begin to draw
the bigger picture of how fossil hominins are
interacting with each other and interacting with the spaces. We've begun to understand
that this cave system is not only a repository
for Homo naledi fossils, it's in part created
by Homo naledi. And that interaction,
the interaction of a species and its landscape, in this case
a subterranean landscape, the interaction of a species
using technology potentially to find ways
into deeper portions, that's something
that's very special. Now, it takes a while for us
to understand the full context of something like discoveries
here, charred animal bones, in the previous slide
you saw a hearth. It takes a while for us
to do the chemistry and to really understand, okay, how much can we
really say about this? What I can say is that
we've found this in an area that previously
we have only evidence of Homo naledi's entry,
so from that standpoint, we're working
with the hypothesis that here we have some
kind of interaction. What we'll continue to do
is excavate and contextualize
this kind of evidence, and that will take us some time. But immediately,
as we discovered that there was fire evidence,
we realized that we had to reevaluate larger parts
of the cave system to try to discover
what other evidence in the cave system
there might be besides the fossil bones
that we've found. Here you see Lee
and Dirk van Rooyen, one of our exploration
team members going out the south entrance
of the cave system, and I'm taking the picture. As we explored the cave system looking for potential cultural
evidence, the cave system, as I said, was three kilometers
underground, and it's complicated. I'm gonna take us, it's an
extensive system underground, and I'm gonna take us in closer
to the central areas where we have naledi evidence that includes the
Dinaledi subsystem here and the Lesedi Chamber here in two different passageways
areas of the cave system. Our entrance to the cave that
we use is here on the right. As we explored the
cave system, we found in another chamber,
the Rising Star Chamber, which is one of the most remote
from surface entrances that we've entered so far,
we've found quite abundant evidence
of charcoal, including really distinctive
chunks of charcoal, scatters of ash,
and animal bones in association with charcoal. We cannot yet say if these
animal bones are left there by naledi, right? There's a lot of dating and a
lot of work that we have to do to understand what
the context is. But we're happening upon a
context which is very unusual. Most human-used caves
have scatters of lithics. They have stone tools
everywhere. They have evidence
of large mammal bones. This is something that's
looking kind of different. And as we study it and probably
in the upcoming year we'll be excavating in this
chamber, we'll be working to understand what the
interactions in the spaces were. Now, let me say a few words
about Charles Darwin. It's Darwin Day at our
celebration of this, and the study of evolution
in a biological sense really began with Darwin. A lot of people read Darwin. A lot of people think about
Darwin and his contributions. Fewer people read his work
on human origins, <i> The Descent of Man,</i> than read <i> The Origin of Species,</i>
his more famous work. Darwin thought really hard
about where humans came from, and he was famously reticent to share his thoughts
in public about this after the publication of<i>
The Origin of Species.</i> A lot of people know
that in<i> The Origin,</i> he sort of concludes
with the line that light will be shed
on man and his origins, but he doesn't shed any light. It takes him another
13 years of work to get to where he's ready
to share his ideas about human origins and human
evolution with the world. In the meantime, other people
are working on this, people like Thomas Huxley, one of his longtime
collaborators, who writes<i>
Man's Place in Nature.</i> People like George Mivart, who's working on
primate evolution and trying to understand
the connections of primates. And Darwin is corresponding
with all of these people and trying to come
into an understanding of where humans fit
in the natural scheme. Darwin made many
contributions to biology. Natural selection, the idea
of biological evolution, the mechanism for evolution. To me, the most central
and important one is the idea that species are
connected by a tree. This was really an
original idea of Darwin. People had thought
about evolution before. People had not
thought about the tree of relationships of species. And the innovation of the tree
gives us the power to understand ancestors
by studying their many descendants and to
understand different stages of the evolutionary process by looking at the branches
that connect at those stages. Darwin famously in his notebook made this diagram of a tree,
the one that says, "I think," at the top. This is the most popular
biology tattoo, by the way. I recommend it. It's actually,
it's an iconic image. This changed the nature
of science, this image. Darwin did not publish
very many trees, and in his entire work
on human origins, he published no pictures
of the tree of relationships of primates or humans to them. But he did think
about this a lot and put in his notebooks
his ideas of the relationships of species. You see my transliteration
of this on the right and Darwin's original notebook
on the left. And you see that he puts humans
on the top left next to the great apes,
gorillas, chimpanzees,
orangutans, and gibbons. They're close relatives,
and a branch yet further from them are the other
catarrhine primates, Cercopithecus, Macaca, baboons, the Cercopithecoid monkeys
as we consider them today. Another branch further out,
the new world monkeys, who we call the
Platyrrhine primates today. And then further, the lemurs. This is fundamentally the tree
of relationships of primates as we understand it today,
with the exception that Darwin didn't quite get
the place of humans correct. Darwin, like most people at
the time, thought that humans have a long branch
that separates us from other great apes,
other closely related primates. Today, we understand that
we are among the great apes. Our branch is most closely
related to a branch that includes
chimpanzees and bonobos, Pan paniscus and troglodytes
on this tree. The human chimpanzee branch is
related to a gorilla branch, Gorilla gorilla,
Gorilla beringei, the western
and eastern gorillas. That branch is connected
to an orangutan branch, which today is occupied
by three living species and many fossil species. Here you see Pongo pygmaeus,
Bornean orangutans, Pongo abeliis,
Sumatran orangutans, and Pongo tapanuliensis,
a recently discovered species in a small area
of Aceh in Sumatra. Their ancestry goes back as long
as three million years ago. The ancestors of today's
great apes go back in time into a time when our own lineage
was also diverse. This isn't as widely
appreciated as it should be. These primates were diversifying in the same timeframe as our
ancestors were diversifying. We have an abundant record
of human origins. This is at the Smithsonian,
a wall of skulls, where you see, I think, more
than 150 different skulls of fossil hominins from the
beginnings of our lineage more than six million years ago
up until the recent past. It's an enormous array
and it's full of skulls. There are relatively few
or complete or partial skeletons of things, but there are some
impressive ones. And as we go closer and closer
to the present, we find partial skeletons
of Neanderthals and more recent modern forms
of humans. We have abundant
skeletal evidence of our evolutionary history. If I look at some
of that evidence, I've put up here sort of
my own wall of skulls, this is not super representative except insofar as I've tried
to put a skull up here for a number of species,
and you'll see 17 of them. And if we look at these skulls and their arrangement,
we can make a tree very much along the lines that
Darwin might've made, where we have species
like our own at the far right and species that are close
on the tree to us that lived in the past
that are now extinct, and as we go
further to the left, species that are progressively
more and more distant from us in terms of their common
ancestry on the tree. If we look at that
leftmost part of the tree and consider the kinds
of hominins that were there, we see hominins that
belong to genera called Australopithecus
and Paranthropus, genera that are today extinct
and have been extinct in the case of Paranthropus
for more than 800,000 years; in the case of Australopithecus,
for nearly two million years. These were diverse and they
lived for millions of years. Today they're gone, but one branch of them survived,
and that branch, after two million years ago,
also diversified. That branch includes all
of the extinct species that we consider to be members of our own genus,
the genus Homo. You'll see here
a wide array of them, humans again
on the farthest right, surrounded by other humans
that are kind of like us in some really important ways,
humans that we today call the Neanderthals
or archaic humans. We see extinct species
like Homo erectus. An extinct species, Homo naledi,
has its place on this tree. Earlier extinct species like Homo rudolfensis,
Homo habilis. These represent ancient
diversity that once existed that our own branch evolved
from and that we have survived. Our origin was an origin
that was not alone. It was an origin that
was among many others. And those others had
their own ways of living, their own ways of thinking,
their own ways of being. We've recently gotten
a lot more evidence about these relationships
from genetics. And it would be wrong for me
to talk about the tree without showing you
a genetic tree. DNA evidence goes back
only in the maximum case in humans so far,
around 430,000 years. We have DNA from an early
population of Neanderthals from Sima de los Huesos,
Spain that is that age. So we know something about
Neanderthals, we know something about other kinds of hominins,
including a fossil population called the Denisovans
discovered initially from this tiny piece
of a finger bone from Denisova Cave in Siberia. Today, we understand that
this was a diverse branch of ancient hominins that
lived alongside Neanderthals and our own species
probably in the eastern and southeastern parts of Asia. And we understand
that today's people and these ancient people had
interactions with others, others that we have echoes
of in the DNA that survived. So those others we cannot yet
identify with fossil evidence. We have genetic fossils
in this sense. The Denisovans are a
great example of that. Initially found
from a finger bone, today we still
do not have a skull that I can show you the face of
that we know to be associated genetically
with this population. We do have a jaw,
and so there's something, and we will have more. There's almost certain
we're gonna have more. But as we go further
back in the past, we discover that these lineages
interacted with each other. They mixed with each other
and they mixed with others. Our tree was a tree in which
our species originated among others, and those
others did not just form part of the scenery; those
others were interacting with and interbreeding with,
in some cases, each other. We come from a tree
with hybridization. That means that these
different species interacted and they interacted
through cultures. Now, as we look at this tree
and see the diversity of hominins that are
part of it and understand that they each had
their way of living, they each had their time,
they each had their place, and they mixed with each other, we can start to assemble
a timeline to try to understand
their interactions. Here we see humans
at the far right again, that's the present day, and there's a density
of evidence of these other kinds
of species coexisting with our species
at various places. We see that there's
Neanderthals at the top and archaic humans
from East Asia next to them. There's modern humans
and archaic humans from Africa. There's Homo naledi that coexists
with early modern humans, and there's the very
small-bodied species from Indonesia, Homo floresiensis,
that also persists until 65,000 years ago. As we trace our branch
earlier in time, there are other times that we see many species
coexisting. These interactions
among these species must have mattered
to our ancestors. They formed a part
of what made us human. Now, I'm very concerned now with understanding
their behavior. How did these ancient hominins
interact? What was their way of living? What were their minds like? When the title of this talk
went out on Twitter, people sort of
kicked back at me. They're like, "Minds, what
are you talking about, minds? "This is fossils,
this is archeology. We're not looking at minds." Minds are our way
of experiencing the world. They're also our only way
of connecting that experience to the world itself. Minds are our interface
with the world around us. That means that they're
also our interface to the other individuals
in the world around us and the interface
to the other species that existed in the world
in the past. When we look at the brains
of ancient hominins, we're not looking at minds. It's a challenge for us
scientifically to try to connect those things
with each other with evidence. Here you see
exceptional endocasts, natural casts formed
inside of skulls. We can study the
insides of skulls and we can look at them
and get a lot of them. An obvious one that I
pointed out earlier is that Homo naledi's brain size
is about a third the size of the other hominins
that coexisted in Africa at the same time. That includes our own species,
Homo sapiens, and archaic forms of humans, sometimes called
Homo rhodesiensis. These crania all date
to the same time. They're very different
from each other in size. An important question is, what difference does
that make to behavior? We know a lot about
the evolution of the size of the brain. This is endocranial volume,
how big the inside of the skull is over time, over the last four million years
in hominins. I'm gonna parse this out a bit 'cause there's a lot
of data here, and that data actually is chunky
when you look at the details. If we look within Africa,
here's the trajectory. Earlier hominins before
two million years ago all have brains around
500 cubic centimeters or so. After that time, some hominins
get bigger brains, but not all. In Africa, you can see that
there's later hominins, including Homo naledi,
that retain that ancestral, smaller brain size
or evolve convergently with earlier hominins
toward a smaller brain size. If I stretch out the
last two million years and look at that timeframe,
you'll see that there are individuals
of Homo erectus throughout this time that approach Homo naledi's
brain size. Small brain size is
something that exists across a long span of time. We're used to thinking
of our species as having been the end of a trajectory,
where that trajectory is toward larger and larger brains. It's actually not the case. Here, you see archaic forms
of humans like Homo rhodesiensis compared
to living, modern humans and our immediate
fossil ancestors. They're a little different
from each other. If we look at evidence from
Southeast Asia and East Asia, you can see that erectus. Then there's these archaic
humans, and they're big in brain size, and then modern
humans are a little smaller. Neanderthals pick up in Europe
after about 430,000 years ago, and modern humans
immediately follow them. This starts to look
kind of chunky. It starts to look like groups. Homo floresiensis persists
in Southeast Asia. So as we look
at the overall tree of the last two million years
of evolution, we see that there's a
pattern of diversification. Hominins are becoming different. Those hominins are all
classified within our genus. They all share common ancestors
with us around two to two and a half
million years ago. They're part of the same tree, but this is a tree that's becoming diverse
in its brain size and as you've seen a hint
of with Homo naledi, it's becoming diverse
in strategies for interacting
with the landscape. So going back to this tree, we're now gonna try to
understand the whole organism. How are these
species interacting? Well, there's other things
to the brain besides its size. This is evidence of the
insides of the skulls of Homo naledi brains. We've studied these, and in a
paper in 2018, our team showed that the frontal lobe
of naledi's brain actually is very human-like
in its organization. It's different
from earlier hominins that had smaller brains. It's actually human
in this respect. There's a structural aspect
to our brains that is shared with a species
like naledi, despite the fact that there's a big size
difference in the brains. That may mean something
very important. This part of the brain in
humans, the left frontal lobe, is essential to forming
language, syntactic language, making sentences
that make sense. We don't know whether
that would've been true in ancestral hominins. We cannot see their forms
of communication directly. We have only a little bit of
evidence about the vocal tract in some forms of hominins,
and it does suggest that Homo shares a vocalization
capacity with humans. Whether it shared a linguistic
capacity or not is unclear. When we think of what
big brains are for, there's been a lot of scenarios,
a lot of hypotheses about this, and technology is maybe one
of the most widely known. These stone points,
which were hafted onto spears, come from Kathu Pan
in southern Africa about 500,000
to 300,000 years ago. This is the archeological
evidence that occurs in the area where
we find Homo naledi. We don't know whether
this evidence was produced by naledi or whether it's
produced by other forms of hominins that may
have also existed at the same time
in the same place. We know that our
immediate ancestors in this timeframe existed and they could well
have been here. There's also chunks of ochre,
a mineral pigment that you can see the
engraved lines on. These are made from rubbing
the ochre onto hard surfaces. We have other chunks of ochre that looked like they were
rubbed on soft surfaces. In southern Africa,
we don't have fossil remains in direct association
with archeology like this. We haven't yet found
archeology like this in the Rising Star Cave,
for example. In North Africa, however,
there are very similar archeological forms, and they
are found in cave layers with early members of our
own species, Homo sapiens. In East Africa at Olorgesailie,
this is a famous site that is just littered
with hand axes that you can go as a tourist
and walk on the walkway and see the hand axe floor
there. Those hand axes are around
a million years old, and they are found
in the same landscape as this fossil skull, which is very similar
to a naledi skull. This was once classified
as Homo erectus. Today, I would say
we don't know for sure. But there are also pigments
at Olorgesailie at a younger timeframe, around
300,000 to 400,000 years old. Pigment use, incision of lines
becomes characteristic on pigments after around
100,000 years ago. Those are the things
that people look at and say, maybe brains are doing this,
maybe this is what communication takes a form,
technology takes a form that requires innovation
from big brains. People used to say
that Neanderthals would've been incapable
of this kind of thing. Neanderthals have
very big brains. Their brain sizes are human
in their size. Over the last two decades,
a revolution in understanding of the behavioral evidence
of Neanderthals has happened. Neanderthals are primarily
a Western Eurasian fossil population. Here's a skeleton
of a Neanderthal that has a hyoid bone, that has a, shows
a human-like vocal tract. The evidence of Neanderthals
as we've pored over it over the years, these fossil
fragments from Krapina in Croatia where I'm gonna be
in a few weeks. This is my friend,
the late Jakov Radovcic who used to curate
the collection. Those fossil fragments,
as we've studied them, we've uncovered evidence
of incised lines on the frontal bone
of one of these. My friend Davorka Radovcic, who is Jakov's daughter
and presently the curator of this collection,
identified eagle talons that have evidence of where
they were strung together. This engraving on the floor
of Gorham's Cave in Gibraltar, more than 60,000 years old,
made by Neanderthals. In addition, pigment spots
in various caves in Spain and southern France appear to be Neanderthal
in manufacture. And Neanderthals abundantly
interacted with pigments. And in a deep cave in France
called Bruniquel, they constructed a circle
out of stalagmites. Hominins are experiencing
their worlds and altering them. They're going into spaces that
other species don't access and they're making things
that are different. They're marking
their environments and they're marking themselves. Now, many people look at this
kind of evidence and think, "Wow, you know,
this is what humans do, so therefore they
must be human." That's kind of a
chauvinistic point of view. And there's nowhere that's
better evidence for this than Southeast Asia where,
on the island of Flores, separated from the
Asian mainland always by a permanent water crossing, even at lowest levels
of sea level, there are hominins that
are very different from us, brains that are around 420
cubic centimeters in size, smaller than naledi's, skeletons that are smaller
than naledi's. This species, Homo floresiensis,
evolved on an island or reached this island
by crossing over permanent water straits. You may say, "Well, okay,
that could happen. That seems like
an amazing thing." They make stone artifacts
that are very interesting, not necessarily super complex,
although these blades are beautifully manufactured
from Liang Bua Cave, where the skeleton that
I just showed you was found. From Mata Menge, these artifacts
more than 800,000 years old indicate floresiensis' presence
on the island at that date. But floresiensis is not alone. On the island of Luzon
in the Philippines is another small-bodied
and small-toothed species that existed up until
the last 100,000 years. This species, discovered in
2018, named Homo luzonensis, we don't have a skeleton of
with a skull that we can say
the brain size of. So we can't say for sure whether
this was like floresiensis, but it looks like floresiensis. These are species that
are crossing water. They're capable
of colonizing new places, living in new ecologies,
and doing so with very different
biological equipment than we're used to having. They're doing it with
small bodies and small brains. And they're doing it
not 100,000 years ago, not 300,000 years ago. They're doing it
800 to a million, 800,000 to a million years ago. That kind of behavioral
complexity is evidenced in the material record. At Wonderwerk Cave
in South Africa, some of the earliest evidence
of charcoal and fire, vastly older than the evidence
that we found in the Rising Star cave system,
indicates that hominins are interacting
with fire going way back. Gesher Benot Ya'aqov in Israel
is an open-air site. It's not a cave site;
it's by the Jordan River. And in this site,
there are hearths where ancient people, 800,000
years ago, roasted pistachios. Another thing people say brains
are for is social behavior, and there's a deep reality
to this. Hanuman langurs are well-known
for their coalitions that they form between males
to compete to displace dominant males
within a group. That kind of ability to ramp on
and ramp off aggression in very intricate
social contexts, something called Machiavellian
intelligence, is something that many scientists think
brain size is evolved for. Grooming, getting along
with other individuals, affiliating with them is
something that people think, this is what brain size
is really for. Mountain gorillas. This is a male mountain gorilla
who's affiliating with and taking care of this
young juvenile. That kind of social behavior
is something that we use our minds for,
right? These are primate minds. I put this slide up here
to remind everyone that I'm gonna show
a disturbing slide next that includes a dead gorilla. So if that's something that
you don't wanna look at, I wanted to alert you to it. Because the other side
of affiliation, the other side of Machiavellian
intelligence, the other side of aggression is
grief and mourning. Here's a gorilla
mourning his mother. We find this in the
fossil record also. At Sima de los Huesos in Spain, the single largest
accumulation of fossil evidence of any hominin,
more than 30 individuals of an early
Neanderthal population, representing a group
of some kind in a pit with their bones
tossed in, probably originally as bodies, many of them the victims of
aggressive or violent deaths as evidenced by perimortem
wounds on their crania and other parts of their bodies. An intentional act
of some kind, deep in a cave. Homo antecessor, also
in the Atapuerca Mountain around 780,000 years ago,
cannibalized. Groups are interacting
with each other in violent ways,
in aggressive ways, and also in many cases
in caring ways, in ways that manifest
the emotion of grief. When I look at the remains
of Homo naledi that we're working on
in the Rising Star cave system, this is what I want to try
to understand. What do these remains tell us
about the interactions of the hominins,
of the individuals, and we are learning that. So as we look across the tree,
we are seeing that there are
different experiences. And those experiences, we have
fragments of evidence of. Our field encounters
more evidence every year, and we find new ways
to analyze it. What I'm telling you about
tonight includes evidence from around the world that
didn't exist five years ago. Very little of this stuff
existed 15 years ago. We're making rapid advances
in understanding the lives and cultures
of ancient hominins. And as we make those advances,
we experience joy, but we think about the emotions
and the joy that the ancient people
also experienced. This is where our emotions
came from. This is where our minds
came from. So I'll leave you
with Homo naledi. I think about it a lot. And you saw the
reconstruction earlier that was very human-like
in its look. And John Gurche,
who's a good friend of mine, a paleo artist,
has a reconstruction that is a little bit edgier. We have our ways
of looking at the past and bringing to it
something different from our own experience. It's a challenge for us
as scientists to try to go beyond our own minds
and understand the minds of others, but it
is so essential because our minds
came from them. The tree that connects us
is the tree that will tell us
how our minds originated. With that, I'll end. And thank you all for coming. I'll be happy to take questions
afterwards. But before I do that,
I just wanna say I really appreciate you all
coming out tonight. It is amazing to be
back in person here in Madison and giving talks. And I'm really happy that
it's happening again. So thank you all,
and I'll be looking forward to coming back again and giving
you the next installment. [audience applauding]
