(swoosh) (typing and electronic chimes) (fast-paced classical piano music) - [Narrator] We are the paradoxical ape: bipedal, naked, large-brained. Long the master of fire,
tools, and language, but still trying to understand ourselves, aware that death is inevitable, yet, filled with optimism. We grow up slowly. We hand down knowledge. We empathize and deceive. We shape the future from
our shared understanding of the past. CARTA brings together experts
from diverse disciplines to exchange insights on who
we are and how we got here, an exploration made possible by the generosity of humans like you. (digital music) (upbeat digital music) - Good afternoon. I'm Katerina Harvati, and
it's a pleasure to be here. And as already mentioned,
I'd like to talk today about the modern human
expansion out of Africa. So as we already heard today, modern humans first evolved in Africa with the earliest
representatives of our species already found more than 300,
or close to 300,000 years ago. However, today we exist
everywhere on the globe as a extremely geographically widespread and ecologically tolerant species. And one of the central questions in modern human origins research, aside from pinpointing the
time and place of origin, is also how this situation came to exist. So, important questions, for example, include when and how did
Homo sapiens disperse out of the African continent, what were the critical factors
enabling this dispersal, whether they might be
ecological or demographic, social, cultural, technological, what was the possible interaction between early modern humans
dispersing out of Africa and archaic hominins
already living in Eurasia, and what are the possible
impacts that this might have had? And so on. But the very first question
that we must answer before addressing anything else is when and how did Homo sapiens
disperse out of Africa. And this is what I'd
like to talk about today. So what do we know? As we already heard in the previous talks, in the previous talk, early
modern humans emerge in Africa starting around 300,000 years ago, and are found all over the continent. But at this time, during this timeframe, we also have archaic hominins, other species that exist in Eurasia. So we have the neanderthal evolution taking place in Western Eurasia, starting already before 300,000 years ago and ending with the
neanderthal disappearance around 39,000 years ago. We also have Denisovans
that exist in East Asia, possibly also in Southeast Asia, and we have late surviving
Homo erectus in Southeast Asia. We also know that the main
expansion of Homo sapiens out of Africa started between 70 and 50,000
years before present, with modern humans reaching Australia as early as 50,000 years ago, and then slightly later reaching
northern parts of East Asia as well as Europe around 45,000 years ago, finally arriving in the New World between 20 and 15,000
years before present, and from there really covering
the rest of the planet. And this dispersal really sets the stage for the world as we know it today. However, the story's not so simple. We have known for many years that Homo sapiens dispersed
out of Africa already in an earlier migration wave. We have evidence from the Near East, from the sites of Skhul and Qafzeh, that shows early Homo
sapiens arriving there between 130 and 100,000
years before present. Recent evidence from a
nearby Misliya cave site has put this early
dispersal of Homo sapiens into the Levant at an even earlier date, close to 180,000 years before present. What's more, in later
periods, so after 100,000, there are neanderthals
found in the same region and no longer early modern humans. Suggesting that these early Homo sapiens did not persist in the
long term in this region. But they were rather, perhaps, replaced by neanderthals here until the later, main out of Africa dispersal
at 60,000 years before present. So, what do we know about this
early Homo sapiens dispersal? We know that it reached the Levant, possibly as early as 180,000
years before present. We generally consider
it a failed dispersal, meaning that the populations
of early modern humans did not actually stay, did not persist, did not survive in the long-term, but were probably
replaced by neanderthals. This kind of dispersal
might have been enabled by environmental shifts
linked to the glacial cycle, such as the one that
we heard about earlier from Jean-Jacques Hublin, and we also have paleogenetic evidence that suggests an ancient
interbreeding event took place between neanderthals and early modern human ancestors even before 200,000 years before present. So, all of this basically means that we have been considering the Levant as a possible contact zone between neanderthals and modern humans where they might have
encountered one another and possibly exchanged
genes at this early time, but also later on in the
main out of Africa event. So this brings me to the site of Apidima and our recent work on
the fossil human skulls from this site. Apidima is situated in the Mani Peninsula in Southern Greece at
the southern-most point of mainland Greece that
is shown here on the map inside the red circle. The site is a cave complex
that was investigated in the late 1970s and 1980s by a team from the University
of Athens Medical School, and it is during this work that two human fossil
crania were discovered encased in a block of rock, breccia rock, found in the ceiling of one of the caves, Cave A, that is shown here. Now here you see the original
photograph from the late '70s showing the rock in the
ceiling, you see it here in red, where the human crania are encased, and as it is about to be removed. And as you can see, this block of breccia is actually rather small, and
the two specimens were found very close to each other. The site itself could
not be dated properly at the time of the discovery, but it was estimated
that the skull breccia, this piece of rock
containing the human remains, was between 150 to 400,000 years old. And a few years ago, a small fragment from one of the skulls Apidima Two, was dated to 150,000 years
before present approximately, confirming this hypothesis. So despite their obvious importance, these fossil crania
themselves remained unstudied and unpublished, and very
little was known about them, except preliminary assessments. Previous observations were made exclusively on one of these
specimens, Apidima Two, which is the one that is better preserved so it actually has a face
and most of the skull, and it was all these observations were based on a handful
of published measurements and a couple of published photographs, and it had been noticed that the specimen has neanderthal or
pre-neanderthal affinities. But the specimen also suffered obviously from distortion and damage after death. As you can see here, is
rather crushed and distorted. So it's interpretation was
actually quite complicated. Now the situation was even worse for the other human specimen, Apidima One, which is much less preserved so there's a lot more of it missing, but it's not distorted. It was cleaned much later so
it was left inside the rock until approximately 2003 when
it was cleaned and removed, and it was never described or published. No published photographs
of it existed before. So approximately two years ago, I was approached by colleagues from the University of
Athens Medical School who asked me to lead a new investigation and reanalysis of this
important fossil material. So in this new analysis, what we did was we applied
virtual anthropology methods to reconstruct the Apidima
specimens virtually, and then we conducted
exhaustive comparative analysis of their anatomy and
their anatomical shape using the methods also
mentioned previously, three-dimensional-geometromorphometrics, so that we could statistically
analyze their shape and elucidate their affinities. Now, because the two crania
preserve mostly different parts of the cranium, we had to
mostly analyze them separately, but we conducted also a combined analysis, and I'm going to show
you the results of this. And finally, we also applied
new uranium series dating in order to shed light on the chronology and actually test the idea that the two specimens came
from the same time period. What I didn't mention before is because they were found so close together, they were generally assumed that they lived roughly at the same time, and they belonged to the same species, and possibly even the same group. So we conducted dating analysis
of the specimens themselves also to test this idea. Was it actually true? In this slide, you see the
process of reconstruction, or virtual reconstruction
of the specimen Apidima Two, and you see on the,
well, on your left side, the three-D model derived from a CT scan. And in the middle what you
see is the segmentation, the virtual dissection
of every bone fragment so that we could, in fact,
isolate each bone fragment, clean the sediments
from inside the cracks, and move the bone fragments back to their original correct
anatomical position. And the final result you
see on the other side, which is one of the
reconstructions that we conducted. Because this kind of reconstruction
could involve some error associated to different observers, we actually produced four
different reconstructions by two different observers
following two different criteria so that we could somehow
correct for any observer error. The result was actually four
quite similar reconstructions, and we use all of these reconstructions as well as their mean
in our further analysis as individual specimens. Things were quite a lot
simpler for Apidima One. I mentioned to you before that
this not so well preserved, but it's not distorted so the
reconstruction of the specimen basically consisted of mirror imaging the better preserved side so as to have a more complete specimen to work with. So let's look at the results. Now we start with Apidima Two
because this is a specimen that is better known and have
been studied somehow before. Its overall dimensions
and cranial bone thickness indicate that it is an adult, and its linear measurements
align it with neanderthals, as it was previously
stated in the literature. It has a whole suite of neanderthal, unique neanderthal features present, including the morphology of its brow ridge and the morphology of the face as well as details of its cranial anatomy. And what about if we
actually statistically look at its shape? And you saw these sorts of plots before in Jean-Jacques' presentation. They are principal components analysis of three-D measurements. The one on the left is the facial based on measurements from the face, and the other one is based
on three-D measurements from the rest of the skull. And what you see here,
again, as you saw before, is modern humans shown in blue, and neanderthals, all the
way out here, shown in red, and these yellow specimens
are pre-neanderthal, so European Middle Pleistocene, and the pink ones are early African, possibly Homo sapiens' ancestors. So in both of these
analysis what we see is that Apidima Two clusters
with neanderthals or between neanderthals
and pre-neanderthals exactly like it had been proposed before. We conducted also a
classification analysis and here you don't have
to look at these numbers, but all you need to know is
that Apidima Two was classified in almost all cases as a neanderthal with very high probability, and only one case as a pre-neanderthal, a neanderthal ancestor. So, all in all our
results on this specimen agree with previous
assessments of this skull. Now turning to Apidima One, now things are a little bit different. Again, the overall dimensions
and cranial bone thickness indicate that it's an adult. And the part of the
anatomy that it preserves, the back of the skull,
actually should show quite a lot of unique neanderthal features that are normally present in neanderthals, but also pre-neanderthals
in this anatomical region. Never-the-less, Apidima One
shows none of these features. Instead, it shows a
combination of ancestral and uniquely modern human
features, and most strikingly, the feature that was
already mentioned before, the rounded aspect of
the back of the skull, which is something that
we normally associate only with modern humans. Do these observations actually hold up when we analyze the shape
in three dimensions? And here again, you see
two different analysis, one based on three-D measurements, reflecting overall neurocranial shape, and one specifically looking at the shape of the mid-line profile
of the posterior part of the cranium. And again, you see modern humans in blue, neanderthals in red, and earlier Middle Pleistocene
Europeans here in yellow, and Middle Pleistocene
Africans here in pink. And in both situations, again,
you have in both analysis, Apidima One plotting
with the modern humans. Classification results
are even more striking. In the neurocranial analysis
is 100% posterior probability that Apidima One is a Homo sapiens. And in the mid-sagittal profile analysis, more than 90% probability. We also conducted a
combined shape analysis. This is the two specimens do not preserve a lot of the same
morphology, but we tried. We wanted to see what they look like if we analyze them together. And we produced a reduced data
set of only the measurements which we could measure
on both of the specimens. And again, now the
results are very similar to what we had before. Apidima Two plotting within neanderthals, Apidima One just outside
the modern human polygon. Classification, very similar
to what we had before. Apidima Two, more than 90% probability of being a neanderthal. And Apidima One, more than 90% probability of being a modern human. So turning now to the new dates, and this was another
surprise waiting for us. As I mentioned to you before, we applied the laser ablation, uranium-thorium dating method, which is an appropriate
method for this time period, and we applied it directly on fragments from Apidima One as well as Apidima Two, also on fragments of unidentifiable bone from the same block of breccia, as well as on the matrix,
the sediment itself. So these are the results. The sediments, the matrix, date to approximately
150,000 years before present. What this means is that this is the time when the dirt, the ground
around the specimens solidified into rock. So you cannot really add
anything to this block after this time, after this point in time. The unidentified bone fragments produced two clusters of dates,
one around 160,000 years, and one more than 200,000
years before present. And the two human specimens fell roughly in these two clusters. Apidima Two dated to 170,000
years before present. Apidima One dated to
approximately 210,000 years ago. Now, this means that Apidima
One is older than Apidima Two so the early Homo sapiens is
older than the neanderthal in this site, and it
also, of course, indicates that the final resting place where these specimens were recovered was not the original place of deposition. How do we explain this? Again, I remind you of where
the specimens were found, in a kind of crack in the ceiling, crack between rocks filled
with this breccia rock. Now, the uranium uptake signatures and the different ages suggest
that these two human fossils actually come from completely
different parts of the cave where they must have later been eroded and fell into a kind of fissure filling where they got thoroughly mixed in with the sediments solidifying
around them at 150,000 years. So in conclusion, Apidima Two belongs to the neanderthals lineage. It fits every expectation
of neanderthal evolution as we know it from the rest of Europe. Apidima One does not. Instead, it possesses a combination of ancestral and modern human features, plots with and is
classified as Homo sapiens, is always closest in overall shape to modern human individuals. So there must have been two populations living in what is now Southern Greece in the Middle Pleistocene,
an early Homo sapiens group approximately at 210,000
years before present, followed by a neanderthal
population at at least, by at least 170,000 years ago. So in fact, the situation as it's shown by the Apidima fossils
seems to be rather similar to what we have in the Levant where early modern humans
appeared to have dispersed early. And in my view, actually
Apidima One probably represents the same dispersal wave as the
Misliya specimen in Israel. Furthermore, in both regions, early modern human seems
to not have persisted in the long term, with
neanderthal populations appearing and sort of replacing modern
humans in both of these regions as is shown in Greece by
the Apidima Two fossil, but also by other sites
exactly in the neighborhood, such as Kalamakia and Lakonis, that have also produced
neanderthal remains. So what are the implications
now for modern human origins? This work shows that the early
dispersal of Homo sapiens out of Africa occurred earlier
and reached much further than previously thought, reaching Europe by 150,000 years earlier than previously suspected. This fits well with evidence from Israel where we have Homo sapiens
presence by 180,000 years ago. It also fits with genetic evidence that has suggested an
ancient interbreeding event between neanderthals and modern
humans before 200,000 years. So, it actually, this
work actually creates quite a lot of new questions. One of the most important ones, perhaps, is was this a failed dispersal? And if so, why? Why did modern humans not persist? Why did they not survive in these regions like they did later on
with the later dispersal out of Africa? But in my view, of course, one of the most important
implications is that perhaps we should consider the broader Eastern Mediterranean region as a possible contact
zone between neanderthals and modern humans. And with this, I would like
to thank all my collaborators and team members, as well
as all the funding agencies, and, of course, you for your attention. (applause) - Thank you, welcome,
and I'd like to start by thanking the organizers
of this symposium and CARTA for inviting us and
hosting us for this session. Our goal today is to
look back at our origins and ask how, where, and when one species of African hominin gained the ability to spread across Africa into Eurasia, replacing all of its hominin relatives? I investigate this through archeology, the material remains of
ancient human behavior. To investigate today's topic, generally archeologists
have looked for evidence of complex cognition,
including the use of language, symbols, and cumulative culture. Ornaments, beads, representational works, abstract designs, and complex technologies are thought to be indicative. When tracking the development
of these complex behaviors, we can look for evidence of
continuity or punctuation, the tempo of evolution. Broadly speaking, the
African archeological record for the period of
interest has been divided into three phases primarily
based on characteristics of stone tool technologies: the Earlier Stone Age, or Ashmolean, the Middle Stone Age,
and the Later Stone Age. The timing of the transition
from one to the next are active areas of investigation, and may not be synchronous
across all regions of Africa. Much of the discussion
about modern human origins has focused on the Middle to
Later Stone Age transition. So we can begin here. The typical MSA is
characterized by largish flakes struck from prepared cores. The resulting flakes,
flake blades, and points were subject to varying forms and degree of retouch or reshaping,
although often less than what is seen in
Mousterian assemblages created by neanderthals. Occasionally, for
discrete periods of time, there are more specific shaped pieces, such as this backed segment or crescent. The Later Sone Age is often characterized by hafted microlithic tools
and numerous implements made out of bone, such
as these bone points. Importantly, in the LSA, people are ubiquitously
making pendants and beads out of shell, bone, and ostrich eggshell. And many argue that these
non-lithic artifacts are really the basis of
the striking contrast with the Middle Stone Age. MSA people had many advanced behaviors, such as sophisticated stone
flaking, active hunting, pigment collection, and
the control of fire. However, some have argued that
they were not fully modern. These colleagues have argued that items indicating
complex symbolic behaviors, such as these ostrich eggshell beads, don't appear until late in the record, appearing abruptly about 50,000 years ago, in marking the onset
of the Later Stone Age. Some colleagues have argued that biological evolution
stimulated these abrupt changes, while others think that
technological, socio-cultural, and demographic changes provide
sufficient explanations. Even while some colleagues were arguing for the punctuated appearance
of modern behaviors with the start of the Later Stone Age, others found evidence for
more complex behaviors within the MSA. These researchers
focused on the complexity of stone tool technologies
and the abundant hearths found in MSA sites, which
stimulated speculation on plant use and the use of fire to manage local environments. In particular, there is
focus on the Howiesons Poort which is characterized by
segments, or crescents, that we saw in the earlier slide. These were made on fine grade materials. This industry was originally
seen as Upper Paleolithic-like, and transitional to the LSA. But there was a problem. The Howiesons Poort
disappears from the record and is followed by a more typical, by more typical Middle
Stone Age assemblages. However, this idea of modernity in the Middle Stone Age stuck. Human fossils had pointed to Africa for the origins of modern humans, and genetic studies were
confirming that all living humans can trace their ancestry back to Africa. The idea that the Middle
Stone Age showed evidence of advanced, even modern behaviors, gained support in the 1990s, especially with the announcement of these two bone assemblages associated with Middle
Stone Age artifacts. At Blombos, the points
were associated with the distinctive Still Bay
variant of the Middle Stone Age characterized by these bifacial points, which Paul Avila also just showed us. Despite the fact that the associations, and therefore the age, of
both these sets of points were questioned by other researchers, these finds stimulated
further consideration of precocious artifacts
in the Middle Stone Age and cemented the idea that
we should find evidence of modern behavior within
the Middle Stone Age. The gradual accumulation model
for behavioral innovations during the Middle Stone Age was proposed. The proposal did acknowledge that something still
changes 50,000 years ago, and that this intensification was the result of population growth combined with environmental deterioration. This led to increased population density, which affected the economy,
technology, and social lives of the groups involved. The increase in population
size would have been due to new technologies and new
risk management strategies, such as long distance exchange. This model was further
supported by additional finds from Blombos of engraved
ochre and perforated shells that may have been beads. Other sites preserved
engraved ostrich eggshell. These generally have
been accepted to support, as support for symbolic
behavior and abstract thinking in our Middle Stone Age ancestors. A big question remains, however. How far back in time do these behaviors go within the Middle Stone Age? Is evolution gradual
within the Middle Stone Age or is there punctuated appearance with the start of the Middle Stone Age? Within the Middle Stone
Age of South Africa, the location of most
of our examples so far, we find a complex ochre processing kit at a 100,000 years ago. An interest in ochre and
non-subsistence shells going back as far as 110,000 years ago. In the last 10 years, we have
recognized that MSA people often heat treat silcrete
by roasting silcrete cobbles in the fire to improve
their flaking properties. This has now been generally
accepted as good evidence of complex technologies
within the Middle Stone Age. Heat treatment is now well-documented in the Late Middle Stone Age, and has been identified
in numerous assemblages, and the technology probably extends back to 164,000 years ago. Beyond these examples,
however, early evidence for symbolic or complex
behaviors is sparse. Beyond the oldest deposits
of Pinnacle Point B, there's still 150,000
years, earlier years, of Middle Stone Age. So far, the archeological
record of South Africa has dominated the conversation. However, as I regularly
remind my undergraduates, Africa is big and it is not one place. North Africa, particularly
Morocco, is also interesting because it has provided the largest sample of early modern humans,
as we heard about earlier from Jean-Jacques Hublin, with some morphological characters that link them with the
earliest fully modern humans expanding out of Africa and into Europe. The Later Middle Stone Age of North Africa is often expressed as the Aterian variant characterized by stemmed
points and scrapers, bifacial foliates, and end scrapers. Turning focus to North
Africa, at Taforalt Cave in late Aterian context,
excavators found perforated shells that were likely used as beads based on polish from use
wear and ochre residue. These are similar in form
to those from Blombos, although the procurement and
potential manufacturing differ. In Morocco, the antiquity of interest in non-subsistence
shells can be pushed back to 115,000 years ago, into
the Maghrebian Mousterian. At Contrebandiers, small shells,
like those from Teforalt, exhibit use, wear, and ochre traces, and may have been used as beads. These were found alongside larger shells also collected already dead on the beach like those from Pinnacle Point 13B. Again, we can ask, how
much further back in time in the MSA can we find similar behaviors? As we go back further in time, of course, appropriately aged deposits become rarer, especially those that have benefited from modern excavation practices. And we get to see these stone artifacts for the third time today. (laughter) So one exception, which
we've heard about earlier, is Jebel Irhoud. These deposits provide a lower boundary for the Middle Stone Age of the region, and preserve evidence of a Levallois-based stone
tool tradition and fire use. However, we have not yet found ochre or evidence of engravings or ornaments. From my current reading of the record, there is continuity from
the late Earlier Stone Age to the early Middle Stone Age. For example, late ESA people
were already interested in using ochre, something
that we find well-established within the MSA, even the
early MSA, at Olorgesailie. However, other signs of complex behavior, such as ornaments, engravings,
or even heat treatment, are extremely limited and not
always well-contextualized. However, to make this comparison robust, there's dire need for more assemblages from both the late ESA and
early MSA from good contexts, especially those that preserve materials in addition to stone. As I have presented here,
within the Middle Stone Age, there is strong evidence of
increasing behavioral complexity such that the later MSA is quite different from the earlier MSA. Moving from the Middle Stone
Age to the Later Stone Age, much of what has been said about the LSA is characteristic of assemblages
that have accumulated within the last 20,000 years. There are unfortunately few examples of well-preserved,
well-excavated, well-dated early Later Stone Age assemblages, especially those with
non-stone components. One exception is Border Cave where the early LSA component preserves perforated marine shells,
ostrich eggshell beads, and bone tools dated to
about 44 to 42,000 years ago. One challenge in further
investigating these developments within the Middle Stone Age
and into the Later Stone Age is that many of these examples that I have mentioned are isolated. Generally, instances
are few and far between, and interpretation is confounded by the archeological challenges of building robust
chronologies and preservation. A second challenge is that the
evidence is especially sparse in the regions where
expanding human populations would have left Africa. Further, we lack direct
archeological evidence of a demographic expansion
60 to 50,000 years ago. Something did change
60 to 50,000 years ago to encourage a population
to expand out of Africa. But what and where? Was the population expansion
found throughout Africa or just within the one region
of the source population? In order to move forward, we
need to develop better defined and more specific models
that allow for the generation of testable hypotheses. We need to further refine the
timing of these expectations and incorporate them
into a regional approach. Variation between regions seems clear, and that's one of the things
I think today's symposium has really highlighted is the variation that we see within Africa. And regions such as
West and Central Africa remain virtually unknown. Again, especially with regard
to the non-stone components of their assemblages. And of course, any behavior-based model needs to be well-integrated with the data from human paleontology and genetics. And so I think symposiums like
what has been organized today is a fantastic way to keep people working on different lines
of evidence integrated, talking to each other, and updated on the types of data
that are being produced. Thank you. (applause) - I'd like to take you all
with me to South Africa where today above the
Rising Star Cave System it looks very much like this. It's beautiful weather there right now. In 2013, Rick Hunter and
Steven Tucker went underground at this site looking for bones. And what I'm gonna show you
is the video that they took going for the first time into a previously unknown cave chamber that we call the Dinaledi Chamber. This is Steven Tucker descending
down a very narrow squeeze that we call The Chute. It's a 12 meter vertical descent, and you see here at the base, bones exposed on the
floor of the cave chamber. This partial skull that you
saw there in that video, this mandible that clearly
from the photographs that they brought out of the cave, looked like a hominin
mandible, not a modern human. It was interesting enough
for my friend, Lee Berger, at the University of Witwatersrand, to organize an expedition to
see what these bones were, to recover them, to bring
them out of the cave to study them, and to
try to understand them. It looked to us like there
might be a large part of a hominin skeleton in the bones that we saw on the surface. And that was big news. But this posed a big challenge because the Rising Star Cave System has a number of very
narrow constraints in it that make it very difficult to pass. And in particular, the one
above the chamber with the bones called The Chute is a
12 meter vertical drop that has a minimum width
of seven and a half inches, 18 centimeters. It was gonna take some
extraordinary scientists to get through this, and
Lee, on a Facebook call, found some extraordinary
archeologists who were capable, not only of the underground skills and the climbing skills necessary to get into this cave chamber, but also the excavation skills necessary to recover and document the bones there. One of these people, Lindsey
Hunter, second from the right, is a staff member here at CARTA now. She is in the room. Several of the others have
worked with us continuously since 2013 in various
aspects of the project. Becca Peixotto at the Perot
Museum of Nature and Science in Dallas right now is
curating the first exhibition of the Homo naledi material
in the United States. Elia Gertoff, Ellen
Foyeregal, Marina Elliott, who's for a long time
coordinated all excavation work in Rising Star, and on the
very right, Hannah Morris. This work is done by a team
of more than 100 collaborators around the world. And I'm gonna try to share some of the big picture aspects of it. I want you to know that
this work is not possible without the tremendous collaboration and in whole-hearted helpfulness and just spirit for the
work both in the field, underground, and also in the laboratory of these extraordinary people. And I'll point out many of them. Some of them are here in the room with us. So, in November of 2013, the expedition spent 28 days underground recovering fossil remains in the chamber. What looked to us from the
surface like possibly the remains of one skeleton, turned out
to represent the remains of many, many individuals. And you see here the
excavators, Marina and Hannah, working on a bone bed that
we exposed very rapidly. All of our work during the
first couple of field seasons were dedicated to excavating approximately 20 centimeters of depth in an area of about 80
centimeters on a side. In that area, we recovered more than 1,500 hominin specimens, representing a minimum of 15 individuals. Study of these specimens in the laboratory convinced us over the
course of a couple of years that we were looking at something that we'd never seen before
in the hominin record. This was a new species,
not like other hominins that we'd found so far, and our team named the
new species Homo naledi. I'll give you a brief tour
of what Homo naledi is like. It's different from us in many
respects, and yet similar. Its hands, for example, have
fingertips that are broad, which are great for exerting a grip through the fingertips. It has wrist bones that are configured more like modern humans and neanderthals than other earlier hominins, but its fingers are also
very curved in its bones, which suggest that it was using
them in a curved substrate while it developed, and
that suggests that climbing was very important to its behavior. Its feet are mostly modern
human-like in their proportions, in the presence of a
longitudinal and transverse arch. And yet, the lateral toes
are a little bit longer on average than ours, and the arch is a little
bit flatter than ours. Its brain, between 450
and 600 cubic centimeters in the specimens that we've recovered, is around a third the size
of modern human brains. This is similar to earlier
hominins like Australopithecus, and not very much like most
other members of the genus Homo. Across its skeleton, it
exhibits a mosaic of traits, some of them very much like modern people, and some of them very much
like very early hominins and not very much like us. Its shoulders are configured to be reaching upwards very easily. That seems like a climbing feature. Yet it's legs are very long and look like they're really
well-made for striding. Its pelvis is a little bit
flattened and more flaring, similar to some of the
earliest hominin pelvis, like Lucy's, and yet
its hands and its jaws resemble our genus in most respects. Its teeth are human-like in size, and yet they're very
primitive in their anatomy. It's an odd combination. I wanted to put this slide up here to remind me to tell you that
we've recovered the remains of individuals of all ages, from neonates through
toddler age individuals, young and older children,
through young and older adults. The distribution of ages in
the sample that we have now, which is stretching up
to around 25 individuals in the cave system, is
very much like neanderthals and early Homo in terms of
not very much representation of older adults. But uniquely, we have a
very high representation of children in the site. And that gives us some important insights into the development of this species, including the fact that
its dental development appears to have progressed
in a human-like pattern, not very much like earlier hominins and other non-human primates. Early canine development
relative to the molar eruption. And so it's a very unique
combination of things. Our team didn't stop exploring
in the cave system in 2013. And Rick Hunter and Steven
Tucker rapidly identified a second cave chamber in the system that had hominin material. Over the course of three years, our team led by Marina Elliott, recovered material from
that second chamber, the Lesedi Chamber, which is 130 meters through the cave system from the first, the Dinaledi Chamber. It's very clear that these
hominins were using large parts of this underground system and
were quite familiar with it. In the Lesedi Chamber, we recovered the really
impressive skeleton of an individual of Homo
naledi, which we named Nao, in addition to parts of at least
two additional individuals. And so we have an extraordinary situation where multiple parts of the cave system are representing a
previously unknown hominin in a situation that we
never found them before in the continent of Africa. Our work to date the site took some time. Eventually we were able to sample directly from the Homo
naledi teeth themselves in addition to geological
samples in the Dinaledi Chamber to narrow down the range of dates for this hominin fossil sample between 236,000 and 335,000 years ago. For a hominin that has a brain a third the size of ours in Africa, this was very surprising to us. It means that Homo naledi
was there at the same time as our immediate ancestors, early humans, early modern Homo sapiens. No one guessed that we had to
share the continent of Africa with something that was
not very much like us at the same time that our
species was originating. That raises many interesting questions. And I'm here to tell you today, that I'm gonna discuss
some of these questions, and they're questions that I
do not have the answers to. I have a lot of information
that's interesting with respect to these questions, and that makes me think very
hard about some of them, and that wakes me up at night sometimes, and certainly wakes up my collaborators if I'm not the one waking them up saying, why isn't this done yet. So you've got these great questions, and I'm gonna review some of them. The first and most obvious one is if Homo naledi is there
250,000 years ago or so, and it's got hands that look
like they're really well-suited to making tools, what kinds of artifacts are associated with it? Are they making the
same kinds of artifacts as Homo sapiens at the same time? Now when we talk about the
Middle Stone Age in Africa, which is this time period in terms of the archeological record, often times people think
about later aspects of the Middle Stone Age, famous things like the
geometrically incised designs on this block from Blombos Cave, things like the Great
Diversification across Africa of different point styles, this is in a figure from Sally
McBrearty and Alison Brooks, and Alison's here in the audience with us. This is a famous thing
about the Middle Stone Age, that you have this
regional diversification. It is only relatively recently that we have developed some more insight about the earlier phases
of the Middle Stone Age, as the Levallois manufacturing technique is really starting to take
over from large cutting tools in earlier traditions. These are the Jebel Irhoud tools, which we saw earlier today
in Professor Hublin's talk, and they're from Morocco, and this is a really unique case in Africa where we have a very
early Middle Stone Age that's associated with
skeletal material of a hominin in a stratigraphic layer. So we know that, oh,
they're the same time. This seems like they're probably
associated with each other. There are almost no fossil associations for other Middle Stone Age, earlier Middle Stone Age assemblages throughout the continent. For example, these hafted
points from Kathu Pan in South Africa are
among the earliest known in the African continent
before 400,000 years old. Who made them? Was it Homo naledi? We don't know. And this creates a problem for us. How do we tell when there are
possibly two cultural hominins in the same continent, who made what? We don't know. These pigment blocks from Olorgesailie, again, Alison's work, are among
the earliest uses of pigment anywhere in the continent, and what Olorgesailie is also known for is a much earlier deposit,
more than 800,000 years old, including lots and lots of hand axes, including this extraordinary
pavement of hand axes that the walkway is built around there. Those hand axes are coevol
with a hominin specimen from Olorgesailie that when
Rick Potts described it, said, well, this looks like a frontal bone that might be a very small Homo erectus. In today's context, this
looks like a ringer for later, 250,000 year old Homo naledi. When we look at small
brain hominins in Africa, they're associated
with, in temporal terms, lots of different technical abilities. The question is how can we pin
down who made these things, and who's responsible for them, and whether they
interacted with each other? This is a serious question. How did Homo naledi manage to coexist with other much larger brain
hominins for as long as it did? We don't know. When we established the earlier part of the Homo naledi ancestry,
like where did it come from, the way that, the tool
that we have to do that is with phylogenetic analysis. And I'm showing you here
a phylogenetic analysis from Mana Dembo and colleagues, including Mark Collard who's
introducing us all in the room, that shows their favored result was that Homo naledi was
connected to neanderthals, modern humans, and other
larger-brained species of Homo, including Homo antecessor. If that's true, that would put the origin of the naledi lineage
earlier than the date of the antecessor fossils, which is around 800,000 years ago. So it makes the naledi lineage something like 900 to a million, 900,000 to a million years old. However, the mixture of
anatomy of Homo naledi makes it very difficult to be confident about how it's related to us. Another analysis by Debbie
Argue and colleagues, they were looking at the relationships of Homo floresiensis in Flores, but they did so by looking across the whole skeleton at traits, and naledi is a really
great sample for that. In their favored analysis, naledi was connected to the
fossils from Dmanisi, Georgia, which are very early
examples of Homo erectus, or in this analysis called Homo georgicus. If naledi is connected to those fossils, then its lineage might be more
than 1.8 million years old. We don't know how long this
branch of our phylogeny was hangin' out in Africa in
coexistence with other species. And it raises the question of how did all this coexisting happen? We've heard already today
from a couple of people about the need to explain
isolation in an African continent where it's clear that anatomical diversity among large brained
hominids is very great. We have a small-brained hominin that existed throughout
this entire time period. Here's a modern human, and you guys have heard a
couple of times already today, and I'll briefly review,
we sort of think we know what the ancestry of
modern humans looks like. You have these early
anatomically modern forms that existed within
the last 200,000 years. Before that, in Africa, you had fossils that many people have described
as early Homo sapiens, but not modern, that existed before 250 back to maybe 400,000 years ago, and across that time and
earlier, back to 600,000, you have some very
archaic looking hominins that many people have
called Homo heidelbergensis, or some Homo rhodesiensis, the Bodo fossil there at the
bottom is an example of that. And that looks like a gradual pattern. It's become apparent that
this is a very diverse group. And in the middle of that
diversity is a species that nobody expected to find. How is this coexistence
possible in an African ecology that is, as large as Africa
is, we think of ourselves as the ultimate competitors. We're supposed to be driving
all these things to extinction, and they're doing fine. (chuckling) That raises the question of whether naledi is part
of this network of mixture that existed across Africa. And I'll give my best
attempt at this mixture, and you're gonna see some
genetics later today, this is drawn from genetics. And so I just wanna illustrate that we've got a
complicated tree of humans. And at the bottom of this
tree I've illustrated here neanderthals and denisovans, you're gonna hear a lot about them later, in a paper that just came out yesterday. Ellen Rogers at the University
of Utah and colleagues have pointed out the possible existence of a superarchaic mixture
into the ancestors of neanderthals and denisovans. So there's complexity in their origins. If we look at Africa, we
see equivalent complexity. We see the diversification
of today's African groups starting before 300,000 years ago, and archaic African groups as
different from today's people as neanderthals and denisovans, that existed and contributed into recent African populations. Who were these people? A lot of times people
look at the stem of this, who's the common ancestor
of us and neanderthals, for instance, and say, well,
there's something Bodo, something Homo heidelbergensisy. But of course, that particular
fossil or others like it might be off to the side somewhere, one of these archaic groups. We look at the earliest
members of our own species, things like the Jebel Irhoud specimen, and say, well, maybe that's
sort of rooting Homo sapiens in some way. But we don't have any genetics. Maybe it's also off to
the side in some way. When we talk about Homo naledi, I'm not gonna put it at
the root of Homo sapiens, but is it one of these
archaic branches that existed that maybe contributed to humans? Does the mixture between
these possible populations explain something about
the anatomy of naledi and its unique mixture? Or is naledi off to the
side, totally separate? Or is it deeper rooted, one of
these superarchaic branches? We don't know. It's a fascinating question. It's one that drives us. Finally, how complex was this behavior that led naledi into these cave chambers? A lot of people have looked at this as maybe an early example of burial. And when we look at these sites and say, why is it that this hominin
is there in isolation in abundance, there is something
very interesting about it. We're studying the bones
to try to determine this, and we're back in the cave
trying to find answers. This is Marapang Ramalaipa
excavating the base of The Chute in 2018. You see here Becca Peixotto
suspended over a ladder excavating what became very
clearly another feature, which is an articulated hominin specimen that we've brought out of
the cave in a plaster jacket we're now studying. Our further explorations
in the cave system have found additional
instances of naledi material, including additional find spots
deep into very narrow cracks off of the main Dinaledi Chamber in places that our team has
to wedge themselves sideways and reach down toward the floor, suspended off of the floor to reach. It's clear that this hominin
was spending a lot of time in this cave, that it was very familiar with the deep parts of it, and that the cave was something
interesting and special in its behavior. And that says something about complexity, understanding that, how
it's connected to us, what it might mean, whether
it's connected to ritual or other things that we've
considered to be uniquely human is something that we're
going to take a long time to try to understand. And so it's an exciting moment because we're finding
these unexpected things, and that's always exciting, but it also means that we
have so much left to do. I hope that all of you will follow us as we continue this research, and as we continue to
make more discoveries in the Rising Star Cave System. Also, I hope that all of you
who are out there digging, keep your eyes open. (laughter) Because there's more of them out there. And I think that we're going to see many more of them very soon. All right, thank you, everyone. I appreciate it. (applause) (upbeat digital music)
(01:39 - Homo sapiens dispersals out of Africa - Katerina Harvati, 21:30 - Continuity or Punctuation in the African Archaeological Record After 500,000 Years Ago - Teresa Steele, 35:56 - How Homo naledi matters to our origins - John Hawks) Where did we humans come from? When did we become the dominant species on the planet? Experts take you on an exploration of the last half-decade of new evidence from ancient DNA, fossils, archaeology and population studies that has updated our knowledge about The Origins of Today's Humans. Recorded on 02/21/2020.