- Welcome, everyone, to Wedne I'm Tom Zinnen. Lab.
I work here at the UW-Madison Biotechnology Center.
I also work for UW-Extension Cooperative Extension,
and on behalf of those folks and our other co-organizers,
Wisconsin Public Television, the Wisconsin Alumni Association,
and the UW-Madison Science Alliance,
thanks again for coming to Wednesday Nite @ the Lab.
We do this every Wednesday night, 50 times a year.
Tonight it's my great pleasure to welcome back to
Wednesday Nite @ the Lab, John Hawks,
professor of anthropology here at UW-Madison.
He was born in Norton, Kansas,
graduated from Norton Community High School,
then he went to Kansas State University
where he studied English, French, and anthropologie.
Then he went to Michigan, got his Ph.D.
in anthropology, did a postdoc at the University of Utah,
and then came to UW-Madison in 2002.
As a testimony to what an extraordinary presenter John is
and what a great story he has to tell.
In the back, your name is?
Sandy, what's your friend's name?
- Me? - You, yeah.
[laughter]
- Paul. Sa- Paul..
Paul just told me this is the first time he's been in a
lecture hall at the University of Wisconsin Madison since 1968.
[laughter]
And I think that's a great testimony to...
[laughter]
To what you can do. I was here last night.
[laughter]
If there's a better storyteller, let me know.
If there's better stories, let me know,
than what John Hawks is going to share with us.
I think in future years people will look back at this recording
and think, man, I wish I was there to see it in person.
And you are all lucky enough to see and hear John Hawks tell us
about his latest update on Homo naledi.
Please join me in welcoming John Hawks
back to Wednesday Nite @ the Lab.
[applause]
- Thank you, Tom.
Thank you, everyone, for coming out.
I've been in the US now for four days, and a week ago at this
time I was in the field working underground with Homo naledi.
And I will tell you that we have some remarkable new findings
from the cave system.
A lot of you have come out for previous talks
that I've sort of presented our initial findings on Homo naledi,
our discoveries in 2013, our publications in 2015.
We've had some incredible things, but we've also had some
incredible mysteries that have arisen.
How did all these bones get into this remote cave chamber?
What are they doing there? When did Homo naledi live?
How was it connected to our species?
These are the things that we've been investigating for the last
four years now, and I can tell you that we can answer some of
those questions and many of the questions have become more
intricate and fascinating for us.
I know that some of you haven't heard all of this story before,
and so I have to present sort of how the cave was found
and where I come into the story and what the excavation was
and why this was news in the first place.
And I'll do that in the first part of tonight's lecture.
And then I'll talk about the publications that we had earlier
this year, where we uncovered a second cave chamber in the
Rising Star Cave, the Lesedi Chamber.
A second cave chamber with more remains of Homo naledi,
with a wonderfully complete skeleton that we've named Neo.
And here's Neo's skull here on the first slide.
At the same time, we determined the age of the fossils,
and the age surprised many people in the world
who did not expect them to be the age that they are.
So it was a wonderful discovery.
But in the last third of the lecture
I want to focus on what we're doing now
and what our most recent field excavation has uncovered.
This is the newest stuff.
This is stuff that I didn't know last week at this time, right?
So I will give it to you unfiltered, and some of it may
be stuff for the history books and some of it I may change my
mind about two weeks from now.
But it'll certainly give you the freshest take on it.
And you guys are the first people
outside of South Africa to know any of this,
except for the people at the University of Alabama
because Lee beat me at this for one day.
One day. [laughter]
So let me-- It's a wonderful privilege.
I say this whenever I present on this stuff,
that we have the involvement of National Geographic
in the project and also of the University of Wisconsin,
who both have enabled us to film
a lot of the original research as it happened.
And we have footage from the initial discovery of the fossils
in 2013, we have footage through the analysis of the fossils,
through the first field expedition,
through this field expedition.
I'll be showing you video later that I took just this month
and that our team took underground this month.
So it's wonderful because I get to show you some of this stuff
and allow people to tell their own story in their own words.
And one of the most important parts of that is
the discovery of the fossils.
So I'm going to show you here Steven Tucker,
who was the first person to enter the Dinaledi Chamber.
- Caving has always been great.
Caving, you want to answer that question
of what's around the next corner.
That's, like, always the question you want to know.
It's mostly fueled by curiosity.
But as you get into caving more and more,
the scientific side of it comes into it.
You want to know how did these places form?
What happened here millions of years ago?
What happened here billions of years ago?
Basically, it creates a fascination
with this whole environment.
In my wildest dreams I would never have thought
that caving would take me to what's happening here.
You can almost call this a bit of an accident.
So my caving buddy and me, Rick,
we were out exploring this cave on a Friday night.
We'd gone into a very remote section of the cave,
a part that I've never been in before,
and in that section we stumbled upon fossils.
Yeah, at first we didn't exactly know what fossils yet.
We started looking around a bit more until we found a mandible,
and that was when we knew this was probably Homo naledi.
That was when we got excited about it.
And since this discovery, it's crazy what's happening here.
- So that was the discovery of the fossils.
It occurred September 13, 2013.
So that's four years ago.
We celebrated the fourth anniversary last month.
Steve, at the time, was studying to be an accountant,
and Rick was unemployed
and basically a super, super clever guy
who loved to cave on the weekends.
And these two guys were exploring for fossils.
They were working with my friend Lee Berger,
who is a National Geographic Explorer-in-Residence
and also a professor at the University of Witwatersrand.
Lee is famous for having discovered
Australopithecus sediba in 2008.
And the story of sediba goes that his son found the fossil.
The story of naledi goes that these cavers found the fossil.
They were looking for fossils, and in this cave,
which is less than 800 meters away
from one of the most famous fossil sites in the world, Swartkrans,
less than one-and-a-half kilometers from Sterkfontein,
the largest fossil hominin assemblage in Africa at the time.
This area that within two kilometers are five famous
hominin fossil sites, no one had ever located
any fossils in this cave.
They're there and these guys found, on that first trip,
not only the Dinaledi Chamber but also
they went through a second chamber, the Lesedi Chamber.
And I'll show you that chamber later.
They didn't recognize at the time what it was.
Only after we began working in the Dinaledi Chamber did they
realize, hey, we've seen something else like this,
maybe you guys would be interested.
Steven no longer is an accountant.
He now is a full-time explorer
for our exploration team, as is Rick.
And we have an exploration team that's in the field every day,
professional explorers, and they are, at this point,
some of the most experienced cave explorers in the world.
Steven, however, can be trusted to review a budget.
[laughter]
The Dinaledi Chamber is in an excruciatingly
difficult to access part of the cave system.
The entrance that we use, the closest entrance to this,
in order to reach the Dinaledi Chamber you have to go through
some very serious vertical climbs.
This is about 40 meters underground.
This is about a 30-meter climb down to the Superman's Crawl.
The Superman's Crawl is a narrow squeeze
with a height of about 10.5 inches.
That's called this-- And I'll show you footage of people going
through it in a while-- It's called this because if you have
any size at all, you have to go one arm first
and squeeze through it this way.
It's all horizontal.
But, more seriously, after climbing a very rugged sort of
rockfall called the Dragon's Back, you can only access this
chamber through a vertical passage that is a width at a
minimum of 7.5 inches and a height of 12 meters.
So it's a 40-foot vertical climb.
That's the only way in or out.
I cannot enter this chamber. Lee can't enter this chamber.
In fact, only a very committed group of people
with the right skills and talents can enter this chamber.
Lee, initially, upon the discovery of this, didn't know
how he was going to get people to recover these fossils.
He put out an ad on Facebook, which later became famous.
"I need people with excavation paleontological skills,
"who can pitch up here next month for no pay,
"and you must be skinny."
[laughter]
"And not claustrophobic."
[laughter]
He recruited these incredible six cavers,
explorers, archaeologists.
All of them, master's, Ph.D. students in archaeology,
including Alia Gurtov from the University of Wisconsin,
but others from the US, Canada, Australia.
Marina Elliott you're going to see a lot tonight.
She is now full-time head of the exploration team
at the University of Witwatersrand.
Just this last month we had Becca, Elen, Hannah,
all out with Marina for our last field expedition.
So the archaeologists who are initially involved
remained committed with us.
Rick Hunter, who you saw in the video,
is married now to Lindsay Hunter.
Don't giggle.
This is the sort of thing that camp people like me
are supposed to prevent from happening.
[laughter] I can't.
I'm not a good chaperone, sorry. [laughter]
I've got three teenage daughters.
I have my priorities.
[laughter]
This is the opening to the chute. I want to show you some video.
We have, on this trip, managed to get some extraordinary video
of some of these passageways through the cave
that we haven't been able to get video in before.
Now we can use a steady cam set up with the GoPro that,
with the right lighting situation,
can actually see into some of these chambers.
So I'm going to show you what it's like to go down this chute.
This is the first time I've shown this video anywhere,
so we'll see if it comes out all right.
- Can you go into that crack?
- Sure, I can go into this crack, here.
Does that make sense? - Yeah.
- This is Becca.
Becca can-- She's just about 4'10", and she can fit into
things that no one else on the team can.
And you're going to see her squeeze into this crack
that none of the rest of the team knew was there.
And we're going to have a camera switch now.
- I'll give this back to you. And then I'll get higher.
- And there goes Marina up this next section of the chute.
- I'm not going anywhere.
- Ok.
- That's a pretty awesome shot right there.
- And once she gets up to the top here, which is just another
second, we're going to see Elen coming up the rest of the way
out of the chute.
So you'll see part of that.
This part of the cave is actually a dotted line.
You saw the map that I showed you earlier had,
it's laser scan data through the entire cave.
We have three-dimensional point cloud data from lasers,
and this is the one part of the cave
that we can't actually get the laser into.
This is what our team goes through every day
to get down to where the fossils are.
- How long does it take?
- Well, the most skilled members of the team can do
this climb in about three or four minutes.
Most people take five to 10.
It depends on how much gear you have to also haul up.
To get from the cave entrance to this point to do the descent
or from here to the cave entrance is about 20 minutes
to 25 minutes through the cave system.
Now, this distance through the cave is about 170 meters.
So if you guys can imagine moving something
like the length of this building, right?
Through the Biotech Center and genetics building, right?
That's 170 meters, more or less.
Imagine taking a half an hour to do that, and you get some idea
of how difficult it is to move through these places.
And these people are all now professionals.
I'm talking about people who cave now for a living,
who are doing it in that time period.
People without these sorts of skills,
you're talking about much longer.
Well, the story of our 2013 expedition.
We all assembled in November of 2013.
Our team went underground.
We were there for 21 days underground.
The team in that time span
recovered more than 1500 fossil specimens.
Almost every single one of them was a hominin fossil specimen.
And it was immediately the largest fossil hominin
assemblage ever discovered in Africa.
It is the second largest fossil hominin assemblage in the world.
It's an amazing, amazing discovery,
and nobody had ever seen anything like it.
It represents every part of the skeleton,
multiple times in most cases.
We have the remains of at least
15 different individuals in this chamber.
What a lot of people didn't appreciate at the time was that
aside from a surface collection, you saw their
bones on the surface, and we collected the bones
from the surface of the entire chamber.
There were around 300 bones and bone pieces
from the surface of the chamber.
The rest of those bones all come from an excavation area
that is less than one meter square.
It's about 80 centimeters on a side.
And the depth of deposit with these fossil hominins
is around 15 to 20 centimeters.
So this is a bone bed
that is totally composed of hominin bone.
Under the hominin bone is sterile sediment,
down at least 50 centimeters.
At the base of that sterile sediment, in the area
that we dug, we found a single tooth of a baboon.
We don't know what that relates to,
but we know quite a lot about its provenience right now
because we were able to estimate the date of this
and the date of the fossil hominins.
So we know quite a lot about these.
At the time, this discovery was unprecedented,
and it was up to us to figure out how to study it.
We recruited a team of specialists who had been
involved in some work in South Africa before, people who'd been
involved in the description of Australopithecus sediba.
And we recruited a team of 35 early career scientists to
join us in describing these fossils for the first time.
That workshop occurred in May of 2014.
We did our work.
We had different anatomical specialists.
It was a tremendous, tremendous experience.
Experts coming in who had done their dissertations
on the vertebral column.
People who'd done their dissertations on the lower limb.
My student, Zach Throckmorton, who had finished here,
was an anatomy professor at Lincoln Memorial University
in Tennessee, had done his dissertation on the foot.
And we had all these specialists come and describe every element
of this hominin and, in the course of that, discovered that
this represents a previously unknown species.
We compared it to every other kind of fossil hominin
that had ever been discovered.
We had cast materials over the originals, in many cases,
available to us to inspect and study.
These are some of them. Homo erectus, on the left here.
Australopithecus afarensis, this Lucy skeleton here,
and another male afarensis partial skeleton.
Australopithecus africanus from South Africa.
Australopithecus sediba,
represented by two partial skeletons.
I'm showing you here the partial skeletons
of the hominin fossil record.
Before Neanderthals, this is what there is.
And so when we have a collection of fossils that is an array,
representing multiple, multiple individuals.
It's really, really powerful evidence.
We identified this as a new species previously undiscovered.
We named it Homo naledi.
Naledi means star in the local Sesotho language,
which is one of the major languages of South Africa.
So naledi is very interesting
because it's different from other fossil hominins in ways
that we did not expect fossil hominins would be.
Now, you guys who know something about evolution know
that evolution is not a straight line.
It doesn't occur in the famous illustration of a hunched
ape-like thing becoming slowly human-like.
[laughter] Step by step, right?
[laughter]
It doesn't happen that way.
Our ancestry was complicated.
There were multiple branches that formed a tree.
And these species are related to each other sometimes in ways
that we don't fully understand because their fragmentary
fossils and it's very hard for us to compare.
You saw the whole skeletons, right?
That was what there was.
Every other piece of thing that we have
is a fragment of one kind or another.
And we have some extraordinary samples of fossil hominin
teeth and jaws and, in some cases, skulls,
but we don't know a lot about how the rest of the body
goes together except from skeletons
that actually put those parts together from one individual.
What we have increasingly discovered over the last 10
to 15 years is that when we have more complete remains, skeletons
like naledi, like sediba, like Homo floresiensis, you start to
discover that the parts don't always go together in the ways
that you might have anticipated.
You might think that even though things are a tree and they're
more complicated than a straight line, nonetheless there's a main
branch, and when things branch off of it, they inherit the
characters of the main branch.
And so there's some sort of order to it.
In fact, for the most part, there's so much parallel
evolution and convergence among the branches of our hominin tree
that it's very difficult to trace
what the main branch might be.
So when we look at naledi's skeleton, it puts together
characteristics that we didn't expect would go together.
The most obvious of these is its brain.
Naledi has a very small brain compared to humans.
It's about 450 to 600 cubic centimeters in size.
That's about a third the size of a human brain.
It's the size of a large orange.
That small brain is in a skull
that has a number of characteristics.
It's got a torus, an angular thickening of bone here
called the angular torus.
It's got a brow ridge
with a groove behind it called the sulcus.
It's got a relatively low, not very high forehead.
It's got a bar here at the back of the skull
called a nuchal torus].
It's got no chin
but a relatively vertical front of the mandible.
It's got a flat face.
These are features that we associate with other species
that we attribute to early Homo,
members of our genus but early in the evolution of our genus.
Fossils that we found that are two million years old.
They're one-and-a-half million years old.
Fossils like Homo erectus and Homo habilis.
So, looking at its features,
it looks like those early human species.
Its brain size is too small.
It's smaller than those early human species.
So there's a bit of a puzzle.
My friend John Gurche is a
tremendously talented Paleoartist.
He's one of the best reconstructors of what fossils
may have looked like in life.
This is his reconstruction of naledi.
And I think it's a very good one.
Obviously, some aspects, like skin tone,
like the hair pattern, have to be speculative in some ways,
but by studying the distribution of these
in human populations, other primates,
John has an educated guess about what they would look like.
But the overall facial profile and everything
is basically this.
This is a nice portrait of naledi.
In this deposit, we have the remains
of at least 15 different individuals.
They are of all ages, from newborn,
or what we would call a perinate, possibly not yet born,
to old adult and every age group in between.
This is a series of six different dentitions that
represent individuals, and they're all of different ages.
This is a toddler, maybe one-and-a-half to two years old.
This is a young child of maybe six or seven.
This is an older child of nine or 10.
Here's an adolescent, a teenager.
Here's a young adult. Here's an old adult.
This is a sample which, for the first time, we can study
development in an entire series of individuals from one place.
One of the things that we've learned by studying this
particular dentition, this older child's dentition,
is that its development is strikingly human-like.
The human-like detail that's maybe the most telling is
that the permanent canine teeth are in.
Those are the canine teeth.
They're all the way in, and the second molar is not yet erupted.
This is a very human-like trait.
Our canines erupt early. Our molars erupt late.
In chimpanzees and gorillas and other primates
and in all earlier hominins that we know about,
the second molar erupts first and the canine is delayed
because the canine is a social signal.
When you erupt your canines, if you're in a primate society,
what you're saying is you're ready for a fight because that's
what you fight with and that's what you threaten with.
And delaying the eruption of the canines is something that
prevents you from getting into fights before you're ready.
In Homo naledi, they have a
very human-like developmental profile.
We can't say what that means socially, but it is very
interesting because they're so primitive in their brain size,
you might imagine that their development
would be very primitive.
But, actually, it's very human-like.
This is a new discovery
that I haven't been able to talk about before.
If we looked at other parts of naledi's skeleton,
it is actually strikingly human-like.
It's feet, for example, are your feet,
if you're a size four women's shoe size.
[laughter] Anybody a size four?
Any size fours in the room? Any size fives?
You're just a little bigger than naledi.
This is naledi's feet. This is a very human foot.
You can see the arch in this foot longitudinal,
the arch medially, mediolaterally.
This is a human foot.
It's got a big toe that's actually a big toe.
It's in line with the other toes.
The other tiny toe bones here are not reconstructed with this
because our foot team actually, you can't tell those apart.
You might imagine, well you can tell them, you know,
second toe from the fourth toe. Actually, you can't.
So we don't put them on because we're not confident
about the placement, but we have all of them.
The hands of naledi are a mixture of human-like
and primitive characteristics.
This is a complete hand.
It was found in articulation in the site.
Here it is.
Folded over fingers, the thumb here.
It's a right hand. There it is.
And I was going to show you,
it's got big, broad fingertips, as humans do,
which are made for gripping hard objects like stone tools.
It's got wrist bones that are arranged in a human-like
pattern, including the crucial difference between the thumb
and the first finger, which helps to buttress
against hard grip forces, again tool use,
but it has tremendously curved finger bones.
The finger bones are curved in a way
that suggests it was grasping onto branches,
or grasping onto something, climbing.
Naledi's shoulder is also really well suited to climbing.
Its shoulders are canted upwards like this
and really well made for reaching over head.
So it's go this interesting combination of traits.
Its lower limb, its feet, very human-like.
Its skull like an early species of Homo, something like
Homo erectus, Homo habilis, but with a smaller brain.
Hands that are really well made for tool making but also
well made for climbing and shoulders made for climbing.
Hips that are really widely flared,
which are very primitive for hominins.
It's like Lucy's hips. It's not like our hips at all.
It is a weird combination of traits.
We've never seen it before.
It has features that we've never seen before
in any hominin species.
So for all those reasons, we're really confident
this is something new that we hadn't seen before.
What we, and this is John's, again, reconstruction of what
naledi would have looked like standing here.
This is Lucy, Australopithecus afarensis.
And the Turkana Boy, Homo erectus.
And you can see that they're really visually different.
If you were looking at erectus and naledi
from a long ways away, from a hundred meters away,
you might think, well, they're not so different.
But as you get closer, you start to notice that
these people don't look like the others.
They don't look like us. Their heads are wrong.
They're standing at sort of an odd posture.
They walk like humans do,
but there's something different about them.
And as you get closer and closer
you start to notice those primitive features.
This is a really different species.
So after our publication
of the species Homo naledi,
we began to work in earnest on our second discovery
in the Rising Start Cave system, the Lesedi Chamber.
This is a layout of the cave as a whole.
This is our cave map. Our entrance is here.
And the Dinaledi Chamber, I've described the pathway to it.
It's over here.
It's around a hundred meters linear distance from the
entrance, but around 160 meters through the cave to get there.
In linear distance in a totally different direction,
is a second chamber, the Lesedi Chamber.
The Lesedi Chamber is not as difficult to access
as the Dinaledi Chamber.
Nonetheless, it's difficult, there are multiple squeezes
between the entrance and the Lesedi Chamber.
I'll show you from the main surface entrance
there is a big squeeze, or I should say a small squeeze,
that we've come to call the Berger Box.
The reason why is that Lee went to the Lesedi Chamber one time
and didn't get back out.
He was stuck at this place.
And the reason why, as you can see, it's an uphill climb, and,
actually, it's easy to go down through it, relatively speaking.
It's about 10.5, no, it's not 10.5 inches.
It's about a nine-inch squeeze.
So Lee can fit through it that way.
I felt that I couldn't so I didn't go that time.
But you have to get purchase against the ground
in order to get back up through it,
and that takes different muscles than it does going up.
And people with long legs have a disadvantage,
and he was stuck there for 45 minutes.
It was crazy.
We had to pull him out like the Winnie the Pooh out of a stump.
[laughter]
So Lee has never been to the Lesedi Chamber again.
[laughter]
And I've never been at all.
There are a number of climbs through this
and then a vertical drop into the chamber.
In this chamber were bones, again, exposed on the surface.
During 2014 and 2015 into 2016, our team, led by Marina
Elliott, excavated in the Lesedi Chamber and recovered the bones
of Neo, in addition to at least two other individuals of Homo
naledi, one juvenile, one young child, and one other adult, Neo.
Neo means gift in Tswana,
which is another one of the local languages.
Neo is one of the most incredible-- Here's Marina
working in the Lesedi Chamber with Ashley Kruger,
our specialist of 3D.
All of these images that we have from the caves and the maps
and everything involve Ashley creating these from the 3D data.
Before I leave this, because it might not be easy for me
to get back to it, I want to point you to this little area
in the chamber is where we found Neo.
His skeleton was mostly in this blind tunnel,
which is off the main part of the chamber.
The main part of the chamber has clearly
had a huge amount of sediment removal.
And where sediment remains there is fossil material exposed,
including up here in the north/south fracture passage,
down here in this part of the chamber, and here in the side.
We speculate that this was once a formation very much like the
Dinaledi Chamber, full of bones, and parts of that have been
removed over time by erosion.
So we've lost bones.
We do have some ideas of where bones go to
after they leave this chamber.
And our current excavations last month
were focused right here, next to Neo.
And we found a couple of additional
small pieces of Neo's skeleton.
We haven't got down past the level that we found Neo at,
however, so there may be more yet to be found.
The Neo's skeleton is one of the most complete
fossil hominin skeletons every discovered.
It is amazing.
I was privileged to be able to lead the description of it
that we published earlier this year.
Here's Neo's mandible.
Here is the most complete mandible
from the Dinaledi Chamber.
You can see that they are nearly identical to each other.
The form of the teeth,
the proportions of the different teeth.
This is a bit more warn.
It's an older adult than this individual.
Cranially, you can see that Neo is a more complete version of
the cranial material we have from the Dinaledi Chamber.
The Dinaledi Chamber hominins
are almost morphologically identical to each other.
They're really, really similar.
They are more similar in things we can measure than humans
from small populations today are similar.
So we're looking at something that's like a population
in terms of its variability.
This is also true when you add
Neo and the other Lesedi material.
You don't add more variation.
They look like they're parts of this same population.
Neo's skull from many angles.
It's a beautiful thing.
Neo also has a relatively complete femur.
And from this we know quite a lot about his size.
This is the best femur we have. This one.
And we've estimated the total length of it from these.
And we have a relatively complete endocast,
about 600 cubic centimeters.
It's a bit bigger than any of the ones
we have from the Dinaledi Chamber.
Okay, so I don't want to go into super detail about biology,
although I get really, really excited about biology.
I do want to say that this is all published in Open Access,
and you guys can download it and read it
and all these charts are there and it's wonderful.
But I wanted to show you a few things.
The brain of naledi, its size, as you can see is smaller
on average than any other species of early Homo.
It is a bit bigger than Homo floresiensis, the very late
surviving hominin species on the island of Flores.
So it's not by any means outside the range of what
we see in things we attribute to Homo,
but it is very much on the small end.
It overlaps with Australopithecus species.
So, small brain.
Its femura are very human-like in their length.
These are erectus femura, and this is naledi's adult.
This is Neo's femur.
This is a juvenile femur of naledi.
This is Lucy's femur, so you can see that,
in terms of height, they're human-like.
Small human, but human-like.
In terms of their teeth, I get really excited about teeth.
Unnaturally so, maybe.
[laughter]
And especially when you've got so many teeth of naledi.
But one of the impressive things about their teeth, this is a
human all the way at the far right, these are all erectus
teeth in between the human here and naledi, and this is a
habilis dentition and these are Australopithecus.
This is africanus and afarensis, right?
So these are all hominin species.
And what you can see is that when you look at naledi's teeth,
they are smaller than the habilis teeth, they're smaller
than erectus teeth, they're more human-sized, but these molars,
the first molar is smaller, the second molar is bigger,
the third molar is biggest.
That's the opposite pattern from what you see in humans.
It's the primitive pattern that you see in Australopithecus.
And when you look at the front teeth, I'll tell you that these
pre-molars, this one in particular and this third
pre-molar, looks nothing like these third pre-molars
of any of these other hominins.
It is really unique.
I say naledi tells us things by the way it looks.
We don't know that these traits
that are unique have functional importance.
I can't tell you that these pre-molars function differently.
I can tell you they're probably a reflection of the species history.
They're pointing to something strange about it.
Naledi had some interesting history.
But, functionally, its teeth are working a lot like human teeth.
More so than these other early species of Homo.
Yeah, this is two sides, and I love this. Here's naledi.
Here are these habilis erectus things.
Two big teeth.
And we think of humans as having relatively small teeth,
and Homo having small teeth because of a high-quality diet.
They're hunting, they're using tools, etc.
Naledi is using more tools.
It's hunting better, or something.
Naledi compared to other species.
And I want to show you the contrast.
Here's naledi, and you can see that in general terms it looks a
lot like something like habilis or something like a small
erectus skull, like this one from the Republic of Georgia.
This is a big erectus skull.
That next to naledi, whoa, they look really different, right?
Very different in size.
Here's a modern human skull, one of the earliest modern humans.
And you can see that this is, I'm going to show you this
right next to each other in just a second.
All right.
Naledi, we worked really hard to figure out
how old these fossils were.
Last time I updated you guys about naledi
I said we don't know how old they are.
And we really didn't.
The fossils are preserved extraordinarily well.
They feel like Neanderthals fossils to me.
They don't, they're not highly mineralized.
This isn't like a dinosaur bone where it's super heavy
because it's turned to rock.
This is bone that's lost most of its organic content
and has some slight degree of replacement with calcite
but not a lot of replacement.
And that tells us something but not as much as you might expect.
I have studied bones that are
two million years old that are like this.
But I've studied bones that are Bronze Age
that are like this as well.
So it's very difficult to tell from the preservation,
but these bones were in a soft sediment.
It seemed like very strange that they might have been preserved
for millions of years in that context.
It would be very exceptional.
So we looked at that and said, well, okay, we can't say how old
these are but there's something very interesting and strange
about the context we found them.
Morphologically, looking at what they look like, everybody said
they looked like fossils that are two million years old.
That's how old they should be.
We had colleagues publish papers saying we believe these fossils
will be two million years old.
Boy, that is the dumbest thing in the world.
[laughter]
To say the evidence points to them being two million
years old but I'll have to wait and see what the geologists say.
This is like setting yourself up for a fall.
So our geology team, here you can see them taking samples.
Here are some of the flowstone samples that they've taken out
of the chamber, including this one, which is super cool
because it's got Homo naledi bone embedded in it, right?
We can figure out the ages of flowstones because they contain
uranium from groundwater, and that uranium decays part of it
over time into thorium and lead.
And so we get an estimate of how old
the flowstone is when it formed.
That doesn't tell us perfectly how old the fossils are, but we
can also look at the teeth of these fossils themselves
and...
with the aid of a laser, take tiny, tiny samples across them
to determine the concentration of uranium
and thorium in the teeth.
And we can also take somewhat larger samples and assess
the amount of electron traps that have been created
in the crystalline structure of the teeth
by ionizing radiation over time.
That technique, called ESR, electron spin resonance,
gives us a direct date on the teeth.
The absorption of uranium by the teeth from the groundwater
gives us a minimum date on the teeth.
The uranium and thorium in the flowstones gives us
an absolute age for the flowstone formation.
We also looked at the tiny quartz grains that are in some
parts of the deposit, which will absorb-- Which will also give
a sign of the ionizing radiation over time
since they were last exposed to light.
That method is called optically stimulated luminescence.
We also looked at the changes in magnetism over time in the
formation of the flowstones in which we can confirm that
all the flowstones in the chamber were formed
during the last 780,000 years since the last major magnetic,
paleomagnetic reversal of Earth's magnetic poles.
I'm listing these because we use six different techniques
from 11 different laboratories,
and we sent samples to these laboratories blind.
We sent them samples and said
you tell us what you're looking at.
And we sent them fake samples.
And we sent the same samples to different labs to see if they
gave us the same answer without corresponding
with each other about their methods.
We, for the first time, did double-blind date testing
on hominin fossil assemblage.
We have what I think is the most rigorous evidence about the age
of this fossil assemblage that's ever been developed.
And all of these methods come together,
all of the different methods.
This chart is too complicated to even read.
But what I was going to say is all the different methods tell
us that these bones were laid down some time
after 335,000 years ago and before 236,000 years ago.
That flowstone that has a bit of naledi in it
is 236,000 years old at a maximum.
The ESR from the crystal structure of those teeth tells
us at 95% probability the teeth are younger than 335,000 years.
So those two bracket the age of the fossils.
Those fossils were put there in the late middle Pleistocene.
This was shocking to everybody, because in the late middle
Pleistocene this is what everyone thought was in Africa.
This is the earliest modern human cranium.
It's about 200,000 years old from Ethiopia.
And here is Homo naledi,
around 250,000 years old, from South Africa.
Naledi lived there at the time our ancestors were evolving.
Our modern human ancestors.
This skull from Zambia is thought to be
around 300,000 years old.
It might be older, it might be younger, but this skull
represents an archaic form of human.
Big brain, more than double the size of naledi's brain.
Big brow ridge. Massive face. Big hominin.
And naledi is there,
less than 1,000 kilometers away, at the same time.
Naledi did evolve two million years ago.
It did branch from out ancestry some time that antiquity.
And it survived alongside of all of these other kinds of hominins
until at least 300,000 year ago.
Naledi was there in the human story and we didn't notice it.
This is shocking.
How is naledi related to us?
I can tell you we don't really know.
I don't know.
I like to put question marks on the tree.
I've got naledi here in its proper age, right?
Here it is, 250,000 years ago, just before modern humans, at
the same time than Neanderthals are evolving in Europe, at the
same time that archaic forms of humans are evolving in Africa,
well after Homo erectus existed but the hobbits hang on.
But how these are related we don't know.
The reason why we don't know is when we look at one set of
characters in one way, these are all from the skull and the
teeth, these features that we looked at, when we look at one
set of characters in one way, naledi looks like it belongs to
the earliest branches of our genus.
It comes from way deep.
And sapiens, Neanderthals, erectus, these primitive
habilis, all those forms are closer to each other.
But if you look at the same data in a different way,
naledi looks like it's connected to archaic humans
and sapiens and Neanderthals,
and erectus and habilis and all these other forms are out.
We don't know how they're connected to us.
For those of you who do biology, this is a Bayesian tree, right?
If you walk down the hallway to the genetics department
and ask them, how should we build a tree of these,
they'll say use this method, and it puts naledi as a
closer ancestor to humans than erectus is.
But if you ask a paleontologist, how should is study this,
they'll give you this tree, and it puts naledi
farther from any other hominin.
I don't know the answer because none of these actually involve
any of the features of the rest of the skeleton
because most of these other species have no skeletons.
So we can't actually compare them.
We've come to a point where the data that we're acquiring from
this evolutionary story are more for naledi than they are for any
other species in our ancestry other than Neanderthals.
It's a cool situation to be in.
It's an exciting situation to be in.
I like it. Don't get me wrong.
I like it so much that last month we went back to the cave
to dig up more of them.
We had some hypotheses to test about the Dinaledi Chamber.
How did the bones get in there?
Oh yeah, this is the one I want.
This is where we enter the chamber.
This is a map of the chamber surface.
These colors are the elevation.
It's high here where we enter the chamber at the chute.
It rapidly descends, and most of the chamber is lower
in its floor elevation.
Where we dug is here.
Where we dug is 15 meters from where we enter the chamber.
Our best hypothesis for how the bones entered the chamber was
that somebody put them down the chute, the same one that we used
that seems to be geologically stable for the last 250,000
years, somebody put the bones down the chute and they formed
as a pile here at the base of the chute and spilled off
and some of them end up here.
But it's not a very satisfying hypothesis,
I'll be honest with you.
And the reason why is that this is where that articulated hand
comes from and an articulated foot and an articulated leg
of a juvenile and a huge concentration of bone.
How did all those bones get over here, 15 meters away, right?
That's the back of the room, right?
From where they apparently entered,
going through two tiny channels?
It's puzzling. It's a real puzzle.
We can rule out-- those of you who don't know the story--
we can rule out lots of ways
that the bones could have entered the chamber.
There's no mark on them from any kind of carnivore or anything.
The bones haven't been eaten. They haven't been crunched.
They haven't flowed in water.
The sediment that they're deposited in
is endogenous to this chamber.
It hasn't come from nearby chambers.
There's no wash of gravel and stuff
that would come in from outside.
They entered the way that we enter.
Whether they go through the rest of the cave
the way we do is uncertain because the rest of the cave
may well have changed quite a lot.
But the Dinaledi Chamber was very much the way it is.
So we went back this month to dig here to test whether there's
actually bones at the base of the chute
because there's a logical hypothesis.
If the bones entered this way, that should be where the
maximum concentration of them should be.
If naledi was putting the bones there, there's some chance
that that's where an artifact might be.
If they were depositing any kind of artifacts with them,
where they enter is probably the most likely spot.
So let me give you just a quick clip.
Here's our excavation in process.
- Now, we are not going to do any [inaudible].
That will not be.
- [inaudible] - Yeah.
- [inaudible] - Okay.
- [inaudible] - Yeah.
- This is the cave entrance, where we have our
command center set up during excavations.
- [inaudible] - So, where was this?
- Down that. -[inaudible] - Okay.
- The pathway to the Dinaledi Chamber
is back in the back there.
Here is Becca Peixotto working at the base of the chute.
Within a very short time of opening an excavation unit here,
which is 50 centimeters on a side, Becca uncovered parts of
a white, chalky flowstone area with some pieces of bone.
And, as they began to work this unit
to uncover the edges of this thing--
This is Montebella coming through Superman's Crawl.
Montebella Sequani is one of our exploration team.
- [inaudible]
- There we go. Look, it's Marina. Help!
[laughing] - Almost.
- I think I can see you.
- I'm going to show you this last clip because as they were
working the edge of that whitened area and determining
its extent, it wasn't clear exactly what we were looking at.
It was clear that there were bone shards in it
and flowstone pieces.
As they began to work, they uncovered a set
of maxillary teeth in position.
So it was clear that what we're looking at is a skull
that is crushed there, mostly gone.
The skull fragments are basically down to nothing.
But they continued to expand that unit
and dig down-- at the end about 20 centimeters down--
they found that the lower edge of this, downslope from the
chute and we're literally talking about a distance like
this, downslope from the chute had a number of much better
preserved bones, including articulated parts of a hand,
including what appears to be
an articulated part of a rib cage, a shoulder.
We're looking in that area at the base of the chute
at a partial hominin skeleton there.
That partial hominin skeleton remains there.
We exposed the outline of it down to where our
excavation unit ended, and we left it in place
because we will have to recover this from the cave whole
in order to study it in the laboratory.
We're going to have to consolidate it, which is going
to be a serious task because these sediments are wet.
And those of you who know archaeological preservation,
you know that wet things are terrible.
We're going to have to replace some of that moisture with a
hardened plastic consolidant so that we can take this out of the
cave as a whole element, through the chute, out and study it by
preparing it in laboratory, get the information that's there to
be had in the arrangement of this skeleton.
But, at the same time, we put some of our best cavers deep
into the Dinaledi Chamber's most difficult to access recesses
in order to try to understand that part of the system.
This is Marina in one of those places,
which we've come to call Hades.
[laughter]
Yeah, I'm going to skip this a second and talk about...
Yeah, okay.
The Dinaledi area where we excavated is here.
There is a tremendous jumble of fallen rock and all kinds of
things back in this part of the cave system that we call Chaos,
and behind that there are passageways
that we've begun to name.
And, as you can tell, with names like
Hades, Purgatory, and Limbo-- [laughter]
These are places that are team has a real problem getting into.
In fact, only the best, smallest cavers
can get into these places.
I'm going to show you a little bit of video
of what it's like to get into this stuff.
So here's Steve Tucker,
and you're going to see him squeeze through this.
And as you're about to see, his helmet isn't going to fit, and
so he's going to take it off to squeeze his head through this.
And what I want to do just is--
Hopefully the video will cooperate,
zoom to the back of this,
and you're going to see Marina at the same passage.
This is all one contiguous clip.
But I just want to show you this is what these are like.
These passageways that are leading off are blind tunnels
that eventually lead nowhere.
But you can see they're tremendously, tremendously narrow.
The temperature in the cave is 19 degrees.
Celsius, sorry.
It's 19 degrees Celsius.
I wanted to show you this because this is Purgatory.
In Purgatory, in Hades, in Limbo, and in Pandemonium,
the named places...
we have hominin fossil remains on the floor.
And this is how our team has to work to get to them.
- [audience] How do they turn around to get out?
[John Hawks laughs]
- I think that that's something you don't ask a lady.
[laughter]
Don't ask me how they turn around to get out.
I don't understand how they do some of the things that they do,
but you can see exactly what's necessary to get there.
There are places back here that Becca cannot get to because it
depends exactly what your height is whether the narrow parts of
your body correspond to the narrow parts of the rock.
It is crazy what's going on back in these passages.
And the fact that we have hominin remains on the floor
of some of these very remote passages is very interesting.
I can't explain it. There they are.
So, in terms of testing our hypothesis about is there bone at the base of the chute:
there's bone in abundance at the base of the chute.
There's articulated bone at the base of the chute. There's a skeleton there.
We've opened a second unit that downslopes slightly that has
additional skull parts that may represent the same individual
or may represent a second individual
in that area of the cave.
That's not really what we expect for a pile of bodies, actually.
It's too good.
We also don't expect these places, which are more than 30
meters from the entrance that we use to enter this chamber,
to have fossil remains in them.
There's a puzzle there, and we don't fully understand
the dimensions of this puzzle.
Okay, I want to quickly say, at the same time,
we were carrying out excavations in the Lesedi Chamber.
And I just don't want to forget that we've done that.
In the Lesedi Chamber, there was also an incredibly constrained
area that we're working in.
This is Elen Feuerriegel,
who is working in the excavation unit.
And you can see that she's enclosed by chert blocks coming
out from the wall of this and is working a few centimeters
below where she's able to be.
To excavate there, we had to erect a ladder
and put up a horizontal one for our team to lie on
and excavate in this very narrow spot.
So we're reducing the level of sediment in this area,
and hopefully we'll open up
part of the sediments where Neo's body was arrayed.
We're hoping to find additional parts of him, and we have found
a couple of pieces in this that might be part of Neo.
So we haven't gotten there to where we'd like to be yet.
Okay, so that's the update that we have for this month.
I have written about it online,
so you can read the summary of this.
Just to close, we have, throughout the entire course of
the project, really worked hard to get material out to the
public as it's happening, as fast as we can to put people
virtually into the cave while we're there,
and to put material out so that we can access it.
And, of course, for me working at the University of Wisconsin,
this is really part of the Wisconsin Idea.
We can do no better to bring people into the science of human
origins than to enable them to participate in the excavation
to the degree that is possible.
And, of course, we're working in a World Heritage site in one
of the most difficult to access places on Earth,
with some of the rarest, most precious things.
We can't bring people into the chamber physically, but we can
use our technology to bring people there virtually.
And I just want to emphasize that during this expedition we
were able to put Internet down into the Lesedi and Dinaledi
Chambers, and we brought schoolkids in through
National Geographic Explorer Classroom, through Skype,
and through other mechanisms.
Here's our team explaining how they're doing the excavations
to a school in South Africa.
We're bringing schoolkids in. Those sessions are on YouTube.
Other schools can watch those. They're all there.
We were able to bring the public in through Facebook Live
using National Geographic's portal.
And on that we had, at the excavation watching us,
50,000 people interacting with us online.
And we continue to do as much of that as we can.
We've published the research in Open Access journals
so that people can download and read them.
Our publications describing naledi have been downloaded
and read more than 400,000 times around the world.
This is the Deputy President of South Africa, Cyril Ramaphosa.
I don't dare say anything about their political situation,
but he could be the next president.
We'll see.
But in addition to having the government engaged at every
level, through science and technology, through tourism,
through the World Heritage authority, we have, the World
Heritage site itself has put the fossils of naledi on exhibit.
They are on exhibit now.
The largest exhibit of fossil hominins
ever put on for the public.
And they're there for people to see and people are seeing them
in huge numbers, unprecedented numbers.
It is an amazing thing to stand there and have schoolkids come
through from all parts of South Africa to see the fossils
for themselves, to repeat, in whatever language they're
speaking when they come in, naledi, Homo naledi.
And it's an amazing story that's told in the exhibition.
So I'm really proud of that.
We started that in May, and that will be there
at least through the year.
So it's been an amazing experience.
It's been an amazing public profile for the research.
It's been some of the most voluminous research.
We have, in the last two years, since our first publication,
published more than 550 peer-reviewed pages of research
on Homo naledi alone.
Our team involves more than 100 scientists around the world
in all aspects of biology.
We are now publishing second round science, what we call
the more complicated analyses done in the laboratory.
Things like the developmental work that you saw on the teeth.
Things like studying the actual wear chipping on the teeth
to compare them to other populations
of humans and other primates.
We're now studying the isotopic signatures in the teeth.
We have not had success in
getting DNA evidence out of the teeth.
We have tried very hard, so far without success.
But we're very hopeful that we will have evidence
from proteins out of the teeth.
So we're going to have some tremendous evidence
coming out about naledi as we move forward,
but what we've learned so far has really transformed the way
that we think about human origins.
It's an amazing project.
It continues and I hope that you'll all continue to follow
along because, certainly from the Wisconsin point of view,
we're going to be there working as long as we can.
All right, thank you, everyone.
[applause]