(crowd clapping) - Thanks everyone. It's a real pleasure to
be here this evening. I wanna start actually by saying something about where I come from. This is a talk about where
we come from as a species, but I think it's relevant
to think about ourselves in this context as well. So 20 years ago, I was graduating college, and I didn't know what I wanted to do. I had gotten a degree
in animal physiology, thought I might wanna be a vet. Applied to vet school,
didn't get in anywhere. I wasn't really sure what I
wanted to do with my life. And I got a job working at
the Boston Museum of Science, and I discovered my passion
and love for science education. At the Boston Museum of
Science, I, I met my wife. I met my, the, the, my
future career as well, because one day my boss asked me to help update our
human evolution exhibit. There had been all these new discoveries in the field of human evolution, and we wanted to update our exhibit. And I said, "Well, I don't know anything about human evolution." And she said, "That's fine. Go to the library and
start reading some books." This was before the internet or before you can Google these things. So, I went to the library and I pulled out some
books by Ian Tattersall. And if you haven't read
anything by Ian Tattersall, I think you should, if you're interested in the talk after today. I devoured his books
and I became obsessed. I caught what was called, the hominid bug. I became absolutely
obsessed with the stories that these old bones tell us, not only about ourselves, but about these ancient
creatures who lived and breathed, and laughed, and cried and eventually died in a context that was fortunate enough for
us, millions of years later, to be able to find their
bones and tell their stories. And so tonight, what I
wanna do is tell you two of those stories. I wanna tell you about two discoveries. Now, the title is talking
about one of those, but in order to talk about one of those, I have to share with you what
came before the discovery of Homo naledi. And to do that, I wanna
take a big step back and just frame all of the fossils, I'm gonna be discussing
tonight in a bigger picture. So we know, and we've known for some time that humans are closely related to the African Great Apes. And there's evidence from genetics. There's evidence from comparative anatomy, from behavioral studies
that we are closely related to the African Great Apes, and in particular to
bonobo's and chimpanzees. Now, this does not mean we evolved from a chimpanzee any more than a chimpanzee evolved from us. We share a common ancestor
with these animals. They live today, they're our cousins, not our ancestors. But if this is the case, if in fact humans and
chimpanzees share common ancestry and the genetics can
pinpoint the date more or less of when we share
the common ancestor, and that's about six
to 8 million years ago, then there should be fossils of things that are neither modern
human nor modern chimpanzee found in fossilized sediments, dating back upwards of six million years on the continent of Africa. And sure enough, we have them. We found lots of these things. In fact, we have about 2000, or prior to what I'll talk about tonight, but 2000 fossils from
the African continent. Now, many of these are isolated teeth or isolated finger
bones, or a femur there, and a humorous over there
or jawbone over here, and a piece of a skull over there. But each of these fragments is precious and helping us reconstruct the story. However, when I tell my students that we have this many fossils, I'll say, "Look, we have
thousands of fossils, and I want you to know a lot of them." They get really discouraged
and they have to study, but, but think about the timescales we're talking about here. We're talking about millions of years, and a million is a 1000, 1000. So, even if I'm being generous and say, "Okay, we have 3000 human fossils." You would still only have a fossil for every 2000 years of human existence. So imagine if I ran up into the stands and grabbed someone's lower jaw, and that became the representative fossil of the last 2000 years of human existence. We'd be missing some stuff, right? Lots of interesting things have happened that wouldn't necessarily be recorded in the jaw of a single individual. And so, we are a growing
science and the fact, in a sense that every time
we make a new discovery it forces us to go back and reevaluate some of
the things we once thought were true about human evolution. And the stories I'm gonna tell tonight are great illustrations of that. Now, with all of these
fossils that we have, we have to organize the
some, some how in some way and contextualize what
happened in human evolution. So big, big, big picture stuff now. what we know is that the
earliest members of our lineage that go back to seven, six, five, even four million years ago, were in a group of animals
that I grouped together and what we call
Ardipithecus or root apes. These things are very, very ape-like. They had grasping big toes
and long curved fingers that would help them climb in the trees. Their brains are about the
size of the chimpanzees brain, but what makes them members of our lineage are that they can walk on two
legs, at least occasionally, and they have small canine teeth. So of all the things that make us human, of all the ways in which we're different from our African ape relatives. The things that seem to
happen first in our lineage, are reduced fang teeth,
compared to other primates. And the ability to at least
occasionally move around on two legs. Around four million years ago, we start to find a
different kind of critter in those fossilized sediments. And that's what we call Australopithecus, represented here by the
famous "Lucy skeleton" discovered in Ethiopia in 1974. Australopithecus is mostly what I study. I love these guys. You're fascinating, fascinating animals. Their brains are only slightly larger than a modern ape's brain. So a gorilla sized brain
and a chimpanzee sized body. So, slight increase in brain size. Again, those canine
teeth are small and dull. They're found exclusively
on the continent of Africa, but what makes them more human-like, is they now are obligate upright walkers. This is what they do. They walk around on
two legs during the day and forage for food. And then they probably
will climb a tree at night to get away from predators. There is evidence of stone tool technology for the first time in Australopithecus, which becomes much more important to members of our own genus, which shows up in the fossil record around two million years ago, characterized by longer legs, more human-like body
proportions, larger brains. We start to see encephalization
or brain enlargement, accelerate in the human lineage. They start to expand their territories to the point that their ranges
now go beyond the borders of the continent of Africa. And we find them in Asia and
eventually find them in Europe. And in Europe, they
evolve into Neanderthals, but back home in Africa, they evolve into our species Homo sapiens. This is supported by genetic evidence and by the earliest fossil
record of Homo sapiens in Africa at about a quarter
of a million years ago, or generously, maybe 300,000
with a new discovery. Homo sapiens is an African species. But again, with our success, our ability to extract
resources from the environment, our symbolic thinking, we, again, start to expand our territories and move into Europe and into Asia. Where we bump into Neanderthals and absorb their genomes into our own, and eventually populate the world, and eventually put our footprints
on other worlds as well. That wonderful moon exhibit
that you have out there, it was quite inspiring that I saw earlier. Now, what I wanna focus on now is this group Australopithecus, because the very first
Australopithecus fossils were discovered in an area
known as the Cradle of Humankind in South Africa. These fossils were found in cave sites, discovered initially in the
1920's into the 30's and 40's. And this is a good time to introduce my colleague and friend
into the narrative here. And that's a guy named Lee Berger. I had known Lee, I've known Lee
for, for about 10 years now. And around that time, Lee had been working at a site at the very top of that map, known as Gladysvale. And Gladysvale is one of the
most beautiful cave sites, I've ever seen. You go into Gladysvale, and there are fossils all over the place. Fossils are pouring out of the rocks, pouring out of the cave walls. And working at Gladysvale
for nearly two decades, Professor Lee Berger discovered
thousands of fossils, fossils of antelopes, and
zebras, and wildebeest, and warthogs, and elephants,
and giraffes, and baboons. But he only found two
fossils of an early human, an Australopithecus. He found a tooth and a
pinky bone, and that was it. So, naturally Lee was getting
a little bit frustrated and wanted to engage in a new project, and a new exploration of this area. And at this time a new
technique was being developed or was being utilized, and
you probably used it too. It's something called, Google Earth. And he used Google Earth
to examine this landscape of the Cradle of
Humankind in South Africa. So this is an animation showing you, as we fly into the Cradle of
Humankind in South Africa. When we get there, it's pretty brown, and arid, and dry. This is classic African landscape, right? Grassland, expanded
grasslands, Acacia trees, littering the landscape. And every once in a while,
shown with these red stars, are clusters of trees. But these trees are stink
wood trees and olive trees. These are trees that actually need water. And the question that Lee
and his geology team asked, "Was where in the world are these trees getting their water from? How are they getting enough water to grow on this otherwise arid landscape?" And what they figured out, was that these trees
were acting as bullseyes for where the caves are. The caves would pull water at their base, seeds from the olive
trees and stinkwood trees who kinda blowing in. And then the trees would
eventually sprout out of these vertical cave shafts. Using this approach, Lee and his team discovered 300 new caves that nobody knew about in
the Cradle of Humankind. One of them, is one we were just circling. That's a cave called Malapa. M, A, L, A, P, A, Malapa. This is what Malabo looks
like from the ground. It's not very impressive, it's just a hole in the ground. It's just a pit. And yet that pit has yielded two of the most complete early
human skeletons ever found, two Lucy's. But they weren't found by
the paleoanthropologist, Lee Berger, they were found
by his nine-year-old son. And this is Matthew telling
the story real quick. - This is where I found it. And here is the rock that looks about the same size as it. And when I turned it over a bit, there was the clavicle sticking out. But when I saw it, I didn't
know it was a clavicle. - So Matthew your father was
working around here, right? - Yes, he was. - And you went off wondering. - Yeah. I just followed
my dog, Tial, down here and then a big rock caught my eye. So I called my dad over, and when he was about five meters away, he started swearing
and he came towards me. He was like, "It's a
clavicle of a hominid." And I was like, "Whoa." (crowd laughs) - So, Matthew initially
saw a clavicle of a replica of it, for anyone who
wants to see it afterwards. If there was any doubt, when Lee flip the rock
over to the other side, there was a lower jaw
that was sticking out, and that lower jaw had the distinctive worn down small canine tooth that you find in humans and
members of the human lineage. So, in just five minutes
at the Malapa cave site, Lee Berger's son had found as many fossils as Lee had found in 20 years
at the site of Gladysvale. So this would have been a great
discovery, no matter what, but as the researchers were collecting this fossilized cave dirt, now that we call Breccia. All of these chunks of
rock had hominid fossils coming out of them. But what I tell my students is, "Look, this isn't an
Indiana Jones science, we don't go into a cave
and just find fossils lying on the surface, instead they're embedded
within this hard rock. And that that fossil
material then has to go back to a laboratory where carefully
underneath the microscope, it needs to be prepared
by skilled preparers." And here in this museum, there's a preparation
lab that's being set up and you can see this for yourself, how this actually works. I have a lot of students that say they wanna be paleon, paleontologists, and they wanna find fossils. And that's great, but
then most of your work, or a lot of your work is done doing this. And they spend an hour doing this and they don't wanna be
a paleontologist anymore. This is a really tedious task. You have to be focused, you have to have enough caffeine in you that you're not gonna fall asleep, but not too much that
your hand is jittery. Because you're using these
tiny little mini jackhammers to slowly grain by grain,
remove the foss live soil or the dirt, the rock away
from the fossil itself. Now that's Lee Berger up in the picture, and maybe you can read the
expression on his face. Lee is not a particularly
patient individual. This takes a long time to do. And Lee staring at this chunk of rock that's really, really, really interesting. Now here is that chunk
from a different angle. This chunk of rock has, clearly
has a bone sticking right in the center of it. That is a humorous, it's
a right upper arm bone. It's from a juvenile,
there's an open growth plate, so that individual was still growing. In a very careful eye, see if I can use the laser pointer here. I don't see it. But up in the upper right-hand corner is a tiny little tooth. And whenever you see a tooth, you get pretty excited
that maybe that tooth is attached to a jaw. And maybe that jaw is attached to a skull, because skulls can tell us a lot, way up in that, in that corner there. Now, if we handed this rock
to our preparers and said, "Okay, prep out this, this rock." A month may pas, and you may have a pile of prepared dirt and a
tooth to show for it. And so there are other
techniques that we can use, and we're using more often
to prepare these fossils. This rock was transported
to a local hospital where Lee Berger's wife
happens to be a radiologist, and she gave it a CT scan. And this is what that scan looked like. Yeah, it's amazing. So, the tooth is sticking out, the bottom is that bright white thing. And then you see the
silhouette of the skull. There is in fact, a skull in that rock. So now with this information, our preparation team was able
to prepare out this fossil with much more care and in
a much more informed way. And what emerged was this
absolutely extraordinary skull. Very often we find fossils
and they're in pieces, and we have to use our
knowledge of anatomy and a whole lot of glue to
put them back together again. But this particular specimen, oh pulled out the wrong fossil, this particular specimen
is in a single piece. This is a replica of it. The original remains in South Africa. But you're welcome to
look at it afterwards. It's an absolutely stunning specimen, but it's not just the
skull that was discovered. Remember I mentioned to you
that there were two Lucy's that were found and here they are. On the left, we think
we have an adult female, on the right, a juvenile male. But a female and male what? Fossils don't come with labels. We had to get to work, head to toe, studying the anatomy of these things to try to figure out whether
there's something similar to fossils we had already
discovered before, or is this something different? Now, it helped to know
the age of these fossils. Our geology team worked
on the cave sediments and determined that these fossils were from creatures that lived about two million years ago around the end of Australopithecus and the beginning of the genus Homo. Head to toe, there were
anatomies in these skeletons that we had never seen in,
in a combination before. And so they were named in 2010, a new species Australopithecus sediba. And what's shown in,
blown up are the teeth, on the left there's a wisdom tooth shown from the adult female
and it's all worn down, that's how we know it's an adult. And on the right, you
can see his two molars, but then there's a circle,
there's the open crypt. His third molar hadn't erupted yet. By human standards, he would
be about 10 years old or so, although we have examine
his teeth more closely, closely, and think that
they would have grown faster than humans do today. And he would've been closer
to about eight years old. Now, whenever we make new
discoveries in science, oftentimes the publicity around them, you hear about the new discovery and a new species being named. And then that's the end of the story. But for the scientist, that's at the beginning of the story. That's when we really
start getting to work, asking questions like, "What did they eat? How do they move? How do they utilize their landscape? How are they related to
other things we knew about?" And so we've been spending
the last 10 years studying these creatures from head to toe. There are studies that
have looked at the hand of this creature, the
foot of this creature. It's a pelvis. I have a student right now
with a paper in a review of what childbirth would have been like in the females of this species. So we're, we're looking head
to toe through this animal to really reconstruct it's paleobiology. What was it's like,
life-like when it was alive. The skull itself has been CT scanned. And what you see in blue
in that rotating skull is an endocast of the brain. So the brain size is about
the same size as chimpanzees are a little bit bigger, but the brain is structured
more like yours and mine. And so this is evidence
that brain reorganization would've proceeded brain enlargement. There are folks who do paleoartistry who have gotten involved
with this project, because of so many bones that we have. This is incredible work
done by Elizabeth Danes, who is a paleoartist. And she has fleshed out these creatures put muscles where we know muscles are, put skin where we know skin would be. And then of course apply quite a bit of artistic license to, to flesh them out. And this is what this two
million year old ancestor of ours would have looked like. Now, I've been working with a team trying to figure out how they moved. Their heels are quite odd. Their ankles are unusual. Their knee looks a lot like ours, but it's different in some peculiar ways. The hip joint looks like ours too, but not quite, there's these
fascinating differences. And so I started working with
a team of physical therapists, trying to think head to
toe through this body, how it would've worked in concert, while this creature was
walking around its landscape. I then involved a student who's interested in video game design, and we started animating the skeleton of how would it have moved? And we just published our
results earlier this year. After two million years
of being in the ground, this is Australopithecus
sediba walking again. Now notice she has long
arms, curved fingers, walking a lot like us, short steps relative to most people. So, it's quite human-like, until you get into this plane, there's a lot of rotation happening. She's doing what we would
call hyper pronation. So, if people walk or run in this manner, it predisposes us to injury, but those unusual anatomies
of Australopithecus sediba, we're anatomical solutions
to the very problems that humans face today,
if they walk this way. And so we think she was adapted to move in this particular manner. Why she was moving this way? We think it was because
she was still very, very comfortable in the trees. Her anatomy of her
shoulder and her fingers, and even her reconstructed
diet would support that. Now, this is what Malapa looks like today. We're still digging at this site, Lee and his team still
digging quite a bit. There is now a beautiful
architectural contraption above that hole in the ground. And so, visitors to
the Cradle of Humankind can go to Malapa and they can
see the excavations happening in real time. And so this is a group of my students that was excavating at Malapa
a couple of summers ago. And we found a small
piece of hominid fossil that we think belongs to the cheekbone of one of these individuals. And so fossils are still being found, and these fossils are
gonna help us test some of the hypothesis that we have developed about this absolutely fabulous creature that was discovered, again,
in 2008 by a nine-year-old. Now, I will remind you that Lee Berger's Google Earth
survey of this landscape, revealed hundreds of caves
that we didn't know about. And I just told you about one of them. So, what about the others? This is an overwhelming task, right? Exploring all of these caves. And so Lee got the word out
to spelunking communities, folks that go into caves
in their spare time, that there is interest in bones. And if you happen to come across fossils or come across bones, there is interest in the
paleoecological community. Enter Steve Tucker and Rick hunter. These folks here, they were, these are not paleoanthropologists. These are amateur cavers. They were in a cave known
as the "Rising Star Cave." This is not one of the 300, but they knew about, or at
least found out eventually about Lee Berger. They were in the Rising Star Cave, and they were looking
at the back of one area that had a particularly tight squeeze. And they went through
that down into a chamber, and when they arrived in that chamber, what they saw was this. Now, I'll remind you earlier in this talk, I said that this is not
an Indiana Jones science, and we never just find bones
lying on the surface of a cave. And yet here are bones just
lying on the surface of a cave. So I was at my desk, I was at Boston university at the time. This was in October of 2013, and I was at my desk working late, and I got an email from Lee Berger and the subject line
said, "Check this out." And there was a photo attached. Have you ever gotten an email like this? (crowd laughs) Yeah. You delete it, right? Obviously a virus said, "You
know you'd gotten hacked, check this out for a picture." Okay. But, but ah, my curiosity
got the best of me and I'm glad it did. Because I clicked on the picture and this came across my screen. I was stunned. And my initial thought was this, this can't be a fossil. That's not how we find these things, this has to be a recent person. We should contact the police. Maybe this was a lost caver
and these are their remains. But, you study the
anatomy a little bit more and you realize that
that can't be the case. So if we look at the teeth for instance, here's a beautiful jaw right here. And one of the things to notice
is how big those molars are. And they get bigger as
you move to the back row of the teeth. So that's a really large wisdom tooth. Humans today, as much as we complain about our wisdom teeth
and have them pulled out of our heads. They're typically not the
largest of the molars, but in the past, in our
ancestors who were snottier, it was the largest of the molars. And that's what we're seeing here. Now, this looked like a single skeleton lying on the surface there. And so, but it's vulnerable, right? And at any point, amateur cavers could
come in to this chamber and scoop up these bones and put them on their mantle piece, right? And they would be gone, they
would be lost to science. So this is a vulnerable set of fossils. And an expedition had to
be put together rapidly in order to retrieve these bones. However, Rick and Steve, even though they could
get into the chamber, didn't know much about fossils. They didn't know much about human anatomy. They didn't have degrees
in anatomy, or archeology, or anthropology, and they didn't
have excavation experience. We needed people who had
a combination of skills. We needed folks who had higher
degrees in anthropology, archeology, or anatomy. We needed folks who had
excavation experience. We needed people who are
comfortable in a cave. We needed people who could work in a team. We need people to go drop, whatever they were doing
and come to South Africa for three weeks to dig up some fossils. And we needed people who
could squeeze through gaps in the rock that narrowed
down to about seven and a half inches. So, to give you an idea
of what this looks like, this is one of those tight
squeezes in the Rising Star Cave. Any volunteers? (laughs) So how are we gonna find these people? Well, Lee came up with the idea of posting on Facebook and Twitter an advertisement that we're looking for skinny scientists who had this set of skills, who had excavation experience, caving experience and
knowledge of human anatomy. And we found six people
who fit that skillset. They're all women, scientists. They came to South Africa in November of 2013 to excavate these remains, this was incredibly difficult work. This is, this is work that,
that was physically taxing. I would imagine quite
emotionally taxing as well, doing, doing this work over this time. These are some of the squeezes
they had to go through. These are images from National Geographic, and this is a really beautiful schematic taking you through the, this,
this chamber of secrets. They, the start is up here. You get to this point, this is where I've turned
around and go back. I wasn't gonna do this. You come down here into what's
called "Superman's crawl." That's one of these really tight squeezes. You have to arrange your
body sorta like Superman flying to get through. And then there is this series
of jagged rocks called, "Dragon's back." That's actually quite
narrow from side to side. And there now is your tight squeeze of about seven and a half
inches down the shoot and into the Dinaledi chamber
where all these fossils are. These are the working conditions. Notice that there are
no shovels down there. No, no excavation equipment. Paleontology is a delicate science, porcupine quills were being
used and plastic spoons and, and little mini trials, and, and, and dental picks. As fossils were found, they
were labeled with flags. 3D laser scanners were
used to document positions of fossils before they were
wrapped up in toilet paper or bubble wrap for transport
back up onto the surface. Those who were quite envious of the folks that were down there doing the excavation, could watch it all on TV. Because cameras were installed down there, as well as some communication equipment to make sure that everything was safe down in that chamber. Now, one of the things I absolutely love about this fossil expedition, was that it was live tweeted. Most fossils are found
in really remote areas and they're found sort of accidentally. Donald Johanson didn't know he was gonna find Lucy the day he found Lucy. And even if there was the ability to tweet it out from there in 1974, there wouldn't have been
much reception anyway. But here it was known
they were hominid fossils down in the ground. And so part of the calculus was, let's let the world
know this as happening. Let's communicate this to
classrooms rooms around the world, and let them know that
fossils are being discovered in real time in South Africa. And so there was all this social media around these discoveries, and ultimately what was
recovered from this cave in those three weeks and then a few additional recovery efforts were almost 2000 fossils of near, of 17 different individuals. Now, to give you a
sense of magnitude here, remember I mentioned earlier that on the entire African continent and the history of our science, we are lucky if we do the math generously to have had 2000 fossil discoveries. If you count up every single tooth and every single tiny little pinky bone. So in one expedition, we effectively doubled
the number of fossils from the African continent. This is extraordinary work. I am so grateful for this work, because it gave me the data, fossils to ask them questions about
our evolutionary history. And this is a good point for me to mention to you that you're really
lucky to be here tonight. And I'm kind of nerding out a little bit, because one of the excavators of the Homo naledi fossils is here in the audience. Dr. Becker, Becca Peixotto is, is here. And yeah, I agree. (clapping) Becca, do you wanna, can you stand so that, people are
looking around. (clapping) (crowd clapping) So for those of you who have questions about what it was like down there and movement through the
cave as often happens, when I give a talk like this. And I don't know, because
I've never been down there as much as I would've loved to have. Becca has agreed to answer
some questions afterwards as well. Now, back to the fossils though, these are super cool fossils and amazingly interesting anatomies. But remember I told you
earlier that fossils don't come with labels, right? We have to do some science. We have to examine the
anatomy of these things to try to figure out are these fossils of things we already knew
about, additional individuals, or is this something different? Now, I went to South
Africa in January of 2014 to work on these fossils
for the first time. Usually when I work on
a set of foot fossils, I have about a dozen of them. And I give myself a,
a about a fossil a day to work on them. So about two weeks to work
on a dozen foot fossils, to draw them, measure
them, 3D laser scan them, CT scan them if need be,
study all the shapes, all the tiny little bumps and grooves where ligaments would attach
and muscles would attach to really work out how
those bones work together in the living organism when
it was still on this earth. Homo naledi had 106 foot bones, okay? This is something I could
not have done alone. And as more researchers
were coming through, it was becoming quite
obvious that we could not have a small team of
researchers working on this. We needed a, either we were
gonna have a small team, working on this and we'd
still be working on it. And none of you would know
about Homo naledi yet. Or we are gonna expand this operation and bring in a lot more researchers. And those researchers ended up being a lot of young career researchers, folks who had just gotten their PhDs, had data sets that needed a question to apply those data sets to. And here we had a question
of what in the world are these things? And so we held a workshop in Johannesburg in the summer of 2014, and folks got to work,
trying to figure out what in the world are these things? This is the skull and jaw
team, led by Heather Garvin in the middle of there. She's a professor at Des Moines University and, and got a degree in
forensic anthropology. And now applies that to paleoanthropology, or at least in the, in
this particular case. This was our torso team. They were working on vertebra and ribs that were discovered in the chamber. Marcus Pfister is a Spanish researcher, in the middle of there Scott Williams from New York university. Sean Hearst was working on the brain. And so the skulls were scanned and we could do internal
reconstructions of the brain. And again, it appeared as
though at a small brain shaped more like yours and mine. We had folks working on the teeth, and the teeth are strikingly human-like, except for those large third molars. And when researchers examined
the internal structure of the teeth, looking at where
the enamel meets the dentin, they had an enamel dentin
shape or morphology that was different from anything anyone had ever seen before. It was entirely unique. Tracy Kibble from the
university of Liverpool, worked on the hand and I
brought the hand with me. The hand is super interesting. It has a long thumb, a thumb that would be
useful for precision grip and even a power grip, but it has these wonderful
curved fingers as well. Quite a primitive looking
hand that would be useful for grabbing onto, while we assume tree
branches or maybe little Homo naledi's grabbing onto their moms. They also had quite a shrugged shoulder, that's more ape-like. I worked on the legs and the feet. We had a large team
working on this material and the legs and the feet are
a lot like yours and mine. However, what was
interesting about the feet is that all of the feet
we found were from, were from flat-footed individuals. It didn't appear as though
any of the Homo naledi's had an arch structure to the foot, and the toes are long and curved. Otherwise though, very,
very human-like foot, and the legs are a lot
like yours and mine, except the joints are tiny. And so from that, what
we've inferred is that, they could walk in an economical way that could get from point a to point B, like you and I can
without using much energy, but they couldn't do
it over long distances. They didn't have the
joints that were adapted for dissipating forces over a long period of time in a long distance. So they didn't have endurance. So they probably had small home ranges. Now, again, this combination of anatomies was something we had never seen before. So in September of 2015, we announced these
fossils as a new species of our own genus, the genus Homo, Homo naledi is what we call them. A naledi means "star"
in the Sotho language, and that is to credit the locality where the fossils were discovered, the Rising Star locality. This publication was in a
journal known as called, "eLife." And this is an open access journal. Sometimes people click on
a scientific publication and it's behind a firewall, and they can't actually read the science. And we didn't wanna do that. We wanted everyone to be
able to read the publication, to read the details if they wanted to. And so we published in
this open access journal. This went viral. I don't know if you followed it, when it happened in September of 2015, National Geographic was a big contributor to funding of this work. And it was a cover piece. It was above the fold
in the New York times. I was having former students contact me, and former teachers got in touch with me about this discovery. It was all over the place. I had cousins, I didn't even
know I had contacting me. And even the satirical website "The Onion" covered Homo naledi (laughs) Now, whenever you make a
new discovery like this, it answers some questions, but it raises new ones. That's the beauty of science, right? Is we can answer some
questions with new discoveries, but it raises new ones
we never even thought to ask in the first place. And one of those questions
about Homo naledi was, "How in the world did all of those bones get down there in that little chamber?" There were no bones of other
animals, large mammals, no antelopes, no zebras,
no wildebeest, no warthogs, no elephants or giraffes. It was just Homo naledi's. 2000 fossils of Homo naledi's. And so you can start to
hypothesize how this could happen. Maybe there's a leopard that specializes in Homo naledi's, and it
was picking Homo naledi's off the landscape and dragging them down into a cave and munching on them. And if that's the case, what would you find all
over the bones, bite marks? Right, so we examine the bones, there are no bite marks. Another hypothesis might
be that maybe a group of Homo naledi's got lost in this cave, and they starve to death. And if that's the case, then all of the bones would be distributed on a single geological layer. As you dug down, you'd stop finding bones. Well, that's not the case, as you dig down, you
continue to find bone. So this happened over a period of time. Maybe there was the occasional flash flood that washed through the area, and swept bones into this chamber. And if it did that, it would sweep in sticks,
and rocks, and bones of other animals. And we don't find anything like that. So this is what we do in science, right? We picture a hypothesis and
then we test it with evidence, and all of those hypotheses, we were just crossing out,
crossing out, crossing out. And what we're left with, is the hypothesis that
this was deliberate, that Homo naledi's after they died, were being transported into this chamber and disposed of deliberately. And that this was happening repeatedly. This was a ritualistic event in the sense that it was happening over
and over and over again, over a period of time. This cave was important to Homo naledi. Now, this is a hypothesis that, that we will need to continue to test. If Dr. Peixotto goes into the Rising Star, Dinaledi Chamber and
discovers a zebra skeleton, they probably didn't drag
a zebra skeleton down there and shove it down into the chamber. So we might have to
reassess this hypothesis, but that's how science works. So one of the other questions that we had, "Was when did this happen?" Now, based on the anatomy, based on the shape of the skull, based on the shrugged shoulders
and the curved fingers, I was going around telling people that this is a better Homo
habilis than Homo habilis. And this is your ancestor to Homo erectus. When we get a date of this fossil, it's gonna be about two million years old, and we're gonna be able
to anchor the origin of the lineage that led to
Homo sapiens in South Africa. And I was wrong, as the geologists got
to work in this chamber, and examined the different rock layers and used really creative techniques of extracting information
from fragments of enamel and quartz crystals that
were in the sediment. What they found was that Homo naledi didn't live two million years ago, didn't even live one million years ago. It lived, or at least these Homo naledi's, lived a quarter of a million years ago, 250,000 years ago. Which is not that long ago, and is right around when
our own species Homo sapiens was evolving on that same continent. These Homo naledi's are
not our extinct ancestors, they're our cousins, they're
our extinct relatives. And so this is a family tree, showing you Homo naledi's position here. We don't know necessarily
who it's related to. This is a hypothesis, right, as all family trees sort of are. So here are humans sharing
this landscape with, we talked about Neanderthals
at the beginning, but now Homo naledi as well, and it's not just Homo naledi. Token was onto something. Quarter of a million years ago, this was an active planet with different upright walking apes, in Africa there was us, Homo sapiens. But also in Africa was this small bodied, small brained creature named Homo naledi, in Europe Neanderthals,
in Asia a population that we know mostly through genetics known as the Denisovans. The hobbits of Homo floresiensis
on the island of Flores, lived at the same time. If you haven't heard
of them, look them up. Super interesting fossils that we still aren't really sure where they
fit into the big picture. And then just last month
was a brand new discovery from an island in the Philippines, Luzon island in the Philippines of a new species called Homo luzonensis, that lived only about 60,000 years ago. Another tiny, tiny, tiny
member of our lineage, where the anatomy's
different from humans today and different even from the hobbit. And so this is a fascinating time in our evolutionary history, and it raises these wonderful questions and these fascinating questions of what happened to Homo naledi when they encountered Homo sapiens? what happened to the hobbits, because they're gone? What happened to Homo luzonensis? We know the Neanderthals were reabsorbed into the human gene pool
as were the Denisevans, but Homo naledi remains this
pressing question for us, is what happened to this population? Now, one of the things
that we've been able to figure out through
the extraordinary work of our excavators and our explorers, was that the Dinaledi Chamber
was not the only place where Homo naledi placed their dead. There is a second chamber
and it's a chamber known as the Lesedi Chamber, equally as difficult I hear to get to, in fact, Lee Berger
himself tried to get down into the Lesedi chamber
and now has an area of the Lesedi Cave System named after him, called "Burgers Box" because he got stuck. I think of sort of the,
the Winnie the Pooh story of Winnie getting stuck in the hole, and they have to wait him out and, and not feed him. Thankfully Lee get out easier than that. But in the Lesedi chamber, what was discovered was a partial skeleton of another Homo naledi. We don't know the age of this chamber yet, but the anatomy is very, very similar to the anatomy found in
the Dinaledi Chamber. And this is an individual
we called, "Neo", which means a "Gift"
in the Sotho language. And this is Neo's skull, which I did bring along as well. And, and folks are welcome to have a look at this after the talk. Now this is the only data slide that I'm gonna put up. And I think it illustrates
an important point that I wanna make now. What you're seeing across the X-axis. So, across the bottom
of the screen is time, three and a half million years ago over in the left-hand corner, today over in the right hand corner. Along the Y-axis is cranial capacity, brain volume, brain size. The yellow line delineates
your average chimpanzee, and the yellow line up here, delineates your average human today. And one of the things to notice is that Australopithecus,
Lucy and her kind, Australopithecus sediba as well, had brains that were slightly larger than your average Chimp. Right around two million years ago, right around when
Australopithecus city ever lived, brain started getting bigger, and bigger, and bigger, and bigger, and bigger, and bigger, and
bigger, and bigger, and bigger. And they topped out
around 30,000 years ago. And ever since then, they've been getting smaller, and smaller, and smaller, and smaller. Little known fact about human evolution is that our brains are smaller than they were 30,000 years ago. For reasons we still
don't fully understand, but that's another lecture. Okay. So over here though, here is Homo naledi, these three dots. And here's Homo floresiensis, look how isolated they are. They're outliers, and they raise fascinating questions of are these dwarfed
versions of this main lineage do the brains get smaller
over evolutionary time, or are there a lot
fossils out there to find? I tend to think it's the latter. Now you don't have to believe
anything I'm saying tonight, we have 3D laser scan these fossils, and we've put them online for everyone. Everyone can check out
the data for themselves, because these fossils
don't belong to Lee Berger and they don't belong to
just a small group of folks. They belong to everyone. This is our story. These are our ancestors
in our extinct relatives, they belong to the world. And so we have posted 3D laser scans of these fossils to this
website, Morphosource. It's free. Doesn't ask for our credit
card or anything like that. You just sign in and you
can download these fossils, and print out these
fossils, if you have access to a 3D printer, which a lot of libraries
do, a lot of museums do. A lot of schools are now
investing in 3D printers. And so after we posted these fossils, we were getting messages
from middle school teachers all around the country,
all around the world, showing us their kids with 3D printouts of fossils that came out of the ground only five years ago. A remarkable, remarkable
effort to make sure that the whole world is
aware of the evidence for our ancestry. Because we want to inspire
the next generation of paleoanthropologists. It's not gonna end with us. And if these discoveries
are any indication, is gonna continue to accelerate. We're gonna have more, and more, and more, and more of these
wonderful discoveries. Because think about it, if Matthew Berger had
tripped over that rock, looked back and then
decided to keep going. Maybe his father would've
continued up the Hill to go look for another fossil site. And we never would've known
about Australopithecus sediba, but it would still be there. And if Rick and Steve looked in the back of the Rising Star Cave System and saw that tiny little squeeze and said, "Ah, let's go home and watch TV instead." Right? We wouldn't know about Homo naledi, and yet those fossils
would still be there. So can you even imagine how many fossils must still be out there
waiting to be discovered? There is so much still for us to discover about ourselves, about
our evolutionary history and about our world. Thank you very much. (crowd clapping)
