- Welcome everyone to Wednesday Nite at the Lab.  I'm Tom Zinnen.  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 at the Lab.  We do this every Wednesday night 50 times a year.  Every now and then, every six, eight, or 10 years, there's a discovery made at a university that you know is likely to be one of those milestone discoveries that for generations into the future people will look back on and say, "That's one of the things we're really "proud of to have been involved with." I think tonight we're going to hear one of those stories.  It's my pleasure to introduce to you, Alia Gurtov of anthropology.  She's going to be talking about first hunters out of Olduvai Gorge, and also the Homo naledi story and how they come together.   Really appreciate the chance to have Alia here tonight.  She was born in Portland, Oregon, went to undergraduate at Wellesley, got her master's degree at the University of Leiden in the Netherlands, and now she's here finishing up her PhD in anthropology. 

 She's got a great story to share.  I wish I could have gone down in the cave.  (laughs) She's going to show why she could, and I couldn't.  (laughs) Please join me in welcoming Alia Gurtov to Wednesday Nite at the Lab.  (applause)  - Thank you so much for having me here tonight.  I'm going to just jump right in.  I am curious about what it means to be a member of our own genus, Homo.  We're Homo sapiens.  What does it mean to be Homo, and what kind of capabilities did early Homo have?  That question has taken me all over the world.  It's taken me to the first site that we find Homo erectus outside of Africa. 

 A site called Dmanisi in the Republic of Georgia.  It has taken me to a neanderthal site called Neumark Nord in Germany.  It's taken me to an early modern human site in South Africa called Pinnacle Point.  And in November 2013 it took me 90 feet underground into a cave in South Africa.   And I could not be hyperbolic about this event.  It was one of the most incredible excavations I've ever been on.   And, in the end, we found over 1500 specimens of the species that now know as Homo naledi.   So I promised one of the members of this audience a schematic that would elucidate the conditions of this cave.  And I'm realizing it really doesn't actually.  All the critical choke points are there. 

 You can see that there's something called Superman's Crawl, which did require a Superman pose to get through.  Basically inching along with fingertips and toes.  There's a climb up Dragon's Back that is a sheer drop on either side.  And then there is that final shute, which isn't labeled there but is the ultimate condition for being small bodied.  It's that 7.5-inch gap that we had to get down.  And, in this case, it looks like a tube.  It's really not, and that's where the confusion comes in.  It's essentially a long crevice, and you're seeing a slice through the width of it.  So if you can imagine it kind of extends forwards and backwards a long ways, but never gets much thicker or much wider than 7.5 inches.  That was the challenge that got me to South Africa. 

  It's about 20 minutes in and out of that cave, if you do it at a slow deliberate pace.  But there were some people that got it down to like 14 minutes, which I wouldn't recommend because it's a pretty challenging environment.   This entrance is the one that we used.  We don't know that this is how Homo naledi got into that cave.  It seems unlikely, but it's still possible.  What we do know was that there was never an entrance any closer in than Dragon's Back because Homo naledi was so far into the cave that it was always in the dark zone.  Always in the dark zone of the cave where no light penetrated and no other animals went.   And just for those of you who like to experience a little bit of claustrophobia.  (laughs) On the left there is the Dragon's Back itself.  And you can see it drops off on either side. 

 And, on the right, you're actually peering straight down that final shute from about three-quarters of the way down it.   And there isn't really much for scale in there, but if you see that rope at the bottom, it's about a quarter in width.  Like the size of a coin.   So it's pretty tight.  It's actually opening up at that point, and then there's another six-foot drop at the bottom.  So we put a ladder in there. (laughs) There's no reason to make it any harder than it has to be.   But anyways these were the reasons that they brought in, as you may have heard, six strong women from the United States, Canada, and Australia.   Was to deal with these conditions.  And they were so worth it.   I've been asked what it's like inside that cave, and I think this image does a lot better than words. 

  There's a kind of peacefulness.  This feeling of ancient long time in there.   - [Crowd] Is that sunlight? - [Alia] No, that's (laughs) that's not sunlight.  No, we put in cameras and lights and com systems and everything else.  That's about two kilometers worth of cabling in there that have since been removed.  But, yeah, we didn't operate just with our headlamps.  We had lights fixed on the area.  So when we got in there, when we got into this cave, into this chamber, the Dinaledi chamber, that entire surface was covered in hominin bones.   This is the last day of excavations.  The first day you would have seen bones everywhere. 

 So the first order of business was to go in there, pick them up.  Well, first scan them in, catalog them, then pick them up, put them in bubble wrap, put them in cases, put them in dry bags, and then haul them out of the cave.   Once that had been done to the surface, which resulted in about 300 bones, we got down to business.  This is where the skull was.  And everyone likes to know what an ancient hominin's face is like.  So we targeted the skull first.   And this took the rest of the three and a half weeks that we were there.  Just getting that bone out and the 1200 others that were right in that tight spot of about 80 by 80 centimeters so less than a yard square.   That's all the excavation that we actually did in that cave.  And it totaled, so the surface bones and the bones that were in the ground in that spot resulted in those over 1500 specimens that came out in the end. 

  This was a day that I remember especially well because this was the day that I managed to pull out a piece of the brow of Homo naledi, and that was the first day that I kind of looked into this hominin space.  So it's a special one in my memory.  But I couldn't be more excited to hand it off to somebody else so that I was no longer in charge of it.  I cannot tell you what the pressure is like.  So here I am doing that, but I was very proud because I had actually carried it out of the cave myself in this case and proven to myself that I could not only go in but also come out carrying things.  So that was a big accomplishment and a great day for me.   In the end...   ...and this isn't the whole thing either.  These are just the biggest pieces.   But what we have here is an extraordinary trove of fossil hominins unrivaled in the continent of Africa. 

  We have at least 15 individuals represented.   We have individuals that are newly borns all the way to the elderly.   And we have multiple examples of almost every single bone in the body.   And that means we can do a lot of kinds of analyses that were never possible before.   And, as you know, we called it Homo.   So what that means is that it belongs to that group of hominins right up here.   The one that eventually gave rise to us.   One of the major questions in our field is, what does it mean to belong to the genus Homo?  What is the significance of calling a hominin Homo and not, say, Australopithecus, like Lucy, or any of the other new genera that came before us that we now know about.  Kenyanthropus, Ardipithecus, Paranthropus if you like to split instead of lump.   And these are the main features that most people agree on. 

 Homo has a larger brain than anything that came before it.   It has a more delicate cranium and face.   It has smaller teeth, which are associated with a diet that's shifted more towards the inclusion of meat.  So we're becoming increasingly omnivorous, increasing that carnivorous component.   A narrow torso, and this is thought to go hand in hand with the smaller teeth, indicating that the guts, which used to be used for fermenting and digesting a lot of leaf matter, are actually shrinking to be smaller.  So they're not needed to do quite as much processing, which is again thought to be a corollary of eating more meat.  And we see that because the hips get narrower and the rip cage gets narrower.   A precision grip.  This is something that we associate with tool use.   A striding gait. 

 So a more dedicated terrestrial adaptation.   And, essentially, what this looks like is a hominin that has shifted from an arboreal and terrestrial adaptation to one that involves walking on the ground, eating a lot more meat, and using tools.  All of those things are something that we tend to associate with the emergence of our genus.   But what people are less in agreement upon is what the capabilities of the early members of that genus, our genus, were.  What were they doing? What were they capable of doing? Cognitively, physically.   And so I've been driven to try to answer this question in a number of ways.  And I specifically looked at how hominins faced the challenges of their environment.  And I've done this by looking at the ways that hominins used stone tools, I've looked at their foraging patterns, and I've looked at their physical adaptations.   And one thing that has emerged in every single case is that I think we've set the bar too low.   I think we've expected that they were capable of too little because what we see in the archaeological record is a central tendency. 

 But even that central tendency can tell us a lot more, if we ask the right questions.   So I mentioned a few of the sites that I've worked at in my time.  But since 2011, I've mostly been working at Olduvai Gorge which is in Tanzania and might ring a bell if you're a long-time fan of National Geographic.  This is where the Leakeys worked, Mary and Louis Leakey.  And so now there are a lot of different teams that work at Olduvai Gorge, and one of them, the one that I've been participating in, runs a field school.  So that's what you're seeing here.  I'm not a natural blonde, if you couldn't tell.  (laughs) So none of these images, I believe, show me as a blonde.  I'm there in the middle, and I'm trying to identify probably a tooth with some of the field school students there.  And that site is FLK North, which is going to come back in a little bit. 

  One of the other things that I do is ethnographic research.  Here with the Hadza, who are especially informative for us and very willing to teach us about how they live in an environment that's very similar to the one that we've reconstructed for Olduvai Gorge.  So a bushy savanna environment.  So they live there.  They rely on natural resources.  They don't cultivate any plants in this particular area.  Although some Hadza do now.   So they can tell us a lot about what the limitations are if you're using a hunter/gatherer adaptation in that environment.   And then I've also done some research in the National Parks in and around Olduvai Gorge.  So this is the Lake Masek National Park, and what we have here is a site of hundreds of drowned wildebeests. 

 It happened probably, I don't know, within the last decade.   The lake level rose so high that most of the wildebeests passing through there drowned.  And we can still see their skeletons along the lake shore there.  This kind of research is not without its dangers.   In 2013 our truck broke down, and I spent the night in my tent listening to lions roaring at me.  But it makes for a great story, and I took pictures of the paw prints the next day so.   Anyway, I mention all of these types of research that I do because it makes for a very holistic approach to understanding how hominins operated in the past.  In no way am I equating what living people are doing today with what they were doing then, but it does tell us about the limits of what is possible in that particular environment if you are a hunter/gatherer.   Olduvai Gorge is known for a lot of things.  One of those is the earliest descriptions of the Oldowan stone tools. 

 Mary Leakey has great descriptions of these in her written work.  So one of the interesting patterns that we see there is that there are a couple of different ways that they do stone tool mapping, the hominins of Olduvai Gorge.  And there's a pattern in which only bipolar napping, which I'll describe in a minute, is done on quartzite, and it is not done on the other raw materials like basalt.  And quartzite and basalt make up the predominate types of raw materials that hominins had available to them then.  So they're making stone tools, but they're using one napping technology on quartzite and a different one on basalt.   And just for a quick description of what that means, free hand napping is what most of us probably imagine when we think of making Oldowan stone tools.  You have your core that you're going to knock flakes off of.  You have your hammer stone and you get a good angle and you knock the hammer stone against the core and you get a flake.  That's what they were doing with basalt, but it's not what they were doing with quartzite.  Instead, they put an anvil in the ground, put their core on top of it, and then struck the core with their hard hammer percussion, which causes somewhat different forces to reverberate through that course and create flakes of slightly different morphology. 

 Slightly different shape.  Still with cutting edges as they needed.  But what I was wondering when I saw this pattern was why.   What can we learn about hominin capabilities? Why were they selecting to use one type of napping technology on one kind of stone and not on another?  So one thing I can tell you straight up is that quartz breaks really easily, but it shatters like glass.  It's absolutely miserable to work with.   On the other hand, basalt is really, really tough.  That means it's durable, but it takes a lot of effort to nap it.  So to start testing this or start asking questions about what the hominins were doing with these raw materials, I and a colleague named Metin Aaron ended up napping 15 basalt cores and 15 quartz cores, and then I had to lug all of that material back to the United States, which is really a process when you're trying to get it out of the country whose major, one of its major exports now is tanzanite.  So any time you're trying to take rocks out of Tanzania, they look at you funny.   So here were the hypotheses that we generated. 

 The first is that quartz flakes are just better.  They just have better cutting edges or better forms that hominins preferred.   And the second hypothesis is that it's actually easier to use bipolar reduction on quartz that it is on basalt.  And these might seem like very simple hypotheses, but it's actually the kind of thing where we shouldn't make assumptions because then you start inferring back on hominins things that we can think about now.  We don't know if they were thinking about them then.   So what did we find?  Well, in terms of the flakes, they're almost identical.  Quartzite and basalt flakes are nearly identical for the size or the mass of the flake, their maximum dimension, the length of the cutting edge and the length of the cutting edge per mass of the flake.  So these are just a bunch of ways to describe what the flakes are like, and between quartzite and basalt almost no difference.   What is different is the rate of production.  And what we see is that hominins were able to knock off flakes from quartzite using bipolar reduction at an significantly greater rate than they could do using basalt. 

 So what's interesting about this is that they recognized the difference in these raw materials in a consistent way.  Employed them consistently differently.   So we can reject that first hypothesis, which I did, and then accept the second one.  And what's really interesting to think about is just the fact that hominins were operating from a position of efficiency.  They were maximizing their efficiency way back.  We're talking over two million years ago.  Or two million years ago at Olduvai, but this was a pattern that we see more broadly.  They were already thinking about the best ways that they could use their raw materials.  This was really fascinating because a lot of archaeologists hesitate to infer any kind of intentionality on early hominin behavior.  And I think this hints that we can start believing them capable of just a little bit more than that. 

  Now, I wasn't completely satisfied that we had answered that question about flake morphology in the first paper, so I defined it and I asked a few more questions about the shape, the length, the cutting edge, the thickness, the width, the breadth, all these other ways to describe the flakes.  And it's true: they're really not much different.  So, there you go.   Next question: how did early Homo become a meat eater? When I described all of those different ways in which Homo is different from the australopithecines that came before it, one of the things that I emphasized was the fact that it looks like it's transitioning to eating meat, both physically and now that we think about it, also behaviorally.  So one of the things that we first associate tools with, which first appeared, now we know, 3.3 million years ago, some of the first evidence we have for what hominins were doing with it is cut marks on bones at sites where muscles would have been detached.  So it looks like they were being used for butchery all the way back.  Our earliest evidence for that is also almost 3.3 million years old.   We also know that that precision grip is something that we associate with the onset or the evolution of early Homo.   And we see over the course of our evolution, the evolution of our genus, a ramping up of the rate of meat eating.  It becomes more and more archaeologically visible through those cut marks that we find on their prey animal bones. 

  So by 1.84 million years ago at Olduvai we have a site called FLK Zinj where we have dozens of animals that are all heavily cut marked, and this is really one of the best and earliest sites that we have for studying hominin meat eating in early Homo.  So, how did early Homo enter this meat eating niche? It's a dangerous one.  It puts them in direct competition with carnivores.   One thing to know about early Olduvai, Paleo Olduvai, between 2 and 1.78 million years ago or so, that's the bed 1 frame, is that it was rather inhospitable.   It's a very open arid environment, it's increasingly seasonal, and it's predominately a grassland.   This lake, this Pliya lake that dominated the center of Olduvai, was saline alkaline.  So it wasn't potable.   What brought hominins to this environment?  Well, recent research in the last 10 or 15 years by a geologist that I work with, Gale Ashley, has shown that they're actually what we call tufas that are outcropping along major faults in the gorge.  And wherever these tufas outcrop, we know that there was a spring at that level at that time.  These would have been freshwater springs, and from phytolith studies of plants from localized sites we can now see that this was actually more of a mosaic environment. 

 We did have acacias and palm trees and other woody vegetation that would have provided a pretty ideal spot for hominins.  I'm going to back up one moment here.   FLK Zinj and FLK North.  FLK North is that site where I've been excavating with students.  FLK Zinj is the site where we have abundant early evidence for hominin meat eating.  They both occur at times that were especially arid.  So especially dry periods in the bed 1 sequence.   But they are both within 200 meters of freshwater springs.  So they were actually in that oasis range despite the rest of Olduvai being relatively open and grassy.   This made them especially attractive sites for hominins. 

  And carnivores.  (laughs)  And we know that carnivores used to prey on hominins too.   Yeah, so, again, how did hominins enter this niche that would enable them to eat more meat but also deal with the carnivores that eat them?  And what I've asked, because hominins are omnivorous but carnivores are specifically carnivorous, is maybe it was possible for hominins to change the way that they were eating.  Maybe they offset the timing of their meat eating seasonally in this highly seasonal environment.   So, again, I turn to the Hadza to develop these hypotheses a little bit more.  What the Hadza do in their highly seasonal environment is really informative.  So, during the dry season, they gather in larger groups around watering holes or nearby watering holes.  And this allows them to set up hunting lines that they use at night to basically use their bow and arrows and shoot at animals that are using the watering hole along known pathways.  So they're able to just set up an ambush site and take off animals pretty easily in the dry season.  In the wet season, they disperse. 

  Their hunting success is a little bit lower, and they're relying on other vegetation to supply the rest of their calories.  And, in fact, meat actually makes up only a small portion of the calories that they get but an important portion.   Some ethnographers have hypothesized that part of the reason to disperse in similar environments for hunter/gatherers is to decrease the rate of predation or the risk of predation by these large carnivores.  So there's not just the fact that the watering holes don't provide as important a centralized place for hunter/gatherers, but also that it's an opportunity to spread out and reduce that competition with carnivores.   But early Homo did not have all of this technology that modern Hadza do, or any other modern people.  They didn't have bows and arrows.  We're almost certain of that.  So, did hominins at FLK Zinj, where we know they were eating a lot of meat, did they eat meat during the same seasons as carnivores did? As carnivores used those watering holes? Or did they offset their operation seasonally to be at watering holes when carnivores were less present?  So I was able to use FLK North and FLK Zinj in a pretty strategic way.  What's great about these sites is that they're so incredibly similar.  The major difference between them is that FLK Zinj was made by hominins. 

 We've got abundant stone tools and cut marks on prey animal bones.  But at FLK North we only have stone tools.  All of the animal bones there, and there's even more than there are at Zinj.  We're talking 30 or 40 large animal carcasses, the bones resulting there from that were all brought in by carnivores.  We find no, almost no cut marks on those bones.  Entirely gnaw marks and chewed ends of bones and everything that indicates a sequence of carnivore activity.  But there are stone tools there.  So we know that hominins were in and out of that region, and we know that they were at least in the same places that carnivores were but we don't know if they were there at the same time.   So, what's similar then between FLK Zinj and FLK North is that they accumulated during the same dry climate regime, they have the same prey species, they were both close to freshwater springs, and they both have those abundant stone tools.  The other thing I should acknowledge is that they are 400,000 years different in time. 

 But when we're talking about two million years ago, well we have to just accept those discrepancies.   It's a little less significant at that time frame than it would be if we were looking at more recent archaeological sites.   So how do we study the seasonal foraging, the seasonal meat foraging of early hominins? There are a lot of different ways to look at seasonality in the archaeological record, but many of them are somewhat destructive.  So I was looking for a way to look at the season of death of the prey animals that hominins were eating.  And the way that I found to do that was to look at the microscopic pits and scratches on the chewing surface of teeth.  So this is a little bit of an indirect approach, but, essentially, if I can determine what season the prey animals died in, then I can link the butchery done by hominins on their skeletons to that season.  So I have linked hominin operation to the season of death of that animal. (laughs) And I've not yet found a really good, concise way to describe that, so I just repeat myself.   And so those microscopic pits and scratches are called dental microwear, or just microwear.  And I needed to prove that this methodology would work.  It's had some success in Europe when people were looking at sheep, goats, horses, deer. 

 But those are all temperate environments with a different pattern of seasonality.  So here I wanted to put it in place in an East African savanna environment.  And so I turned to a collection that I had helped to create of impala that were killed by Hadza in wet and dry seasons.  And I analyzed them using dental microwear analysis to see if I could actually distinguish between those that had died in the wet season and those that had died in the dry season.  So the first thing I checked after I ran those samples was whether they matched up with other dental microwear analyses of impala that people had done at other sites.   Nobody had looked at seasonality for these specimens, but what I did find was a sample that had been analyzed from the Field Museum that showed impala that had only died in the dry season and their microwear.  And so I ran a bunch of different variables through because there's a lot of different ways that we can look at microwear, and I put one example up here, heterogeneity, which is the variation of pits and scratches across that occlusal surface, the chewing surface.  And what you can see is that they generally overlap pretty well.  So my impala sample from the Hadza in Tanzania and this impala sample that's from Botswana both look pretty comparable, which is a good indication that I did those samples right.   So like I said there are a whole bunch of different variables. 

 I'm actually going to ignore most of them because only one of them significantly distinguished between wet and dry seasons.  So I kind of chucked the rest.  And what I focused in on was this variable: heterogeneity.  And I have heterogeneity at different scales.  So I can look at how different the tooth is between nine different segments, if I divide up the surface into nine segments, or I can look at how variable it is when I divide it up into 81 segments.  And when I divide it up into 81 segments, that's when I actually see a distinction between wet season and dry season.  And this is actually really good because what it means is that we can learn a lot about impala diet if we were so inclined by looking at dental microwear regardless of when the animal died.   But what I'm also seeing is that it looks like there's some environmental difference that is subtle but significant enough to tell me whether it's a wet season or dry season sample or both.  So what I could see when I used a Mann-Whitney U equation to analyze my wet season and dry season samples to see if they were statistically distinct is that, yes, they are.  Thank goodness because that was my entire dissertation resting on the ability to distinguish between these. 

 (laughs) I can't tell you, but I did celebrate that day.  (laughs) Yeah, so it's right on the cusp there, but .049 is significant.   And just for another way to visualize that, the dry season has lower values for heterogeneity than the wet season.  This is just looking at that range.  What's interesting is that it actually seems variance is more significant than mean between these two samples.  So that's something I'll be playing around with a little bit more.  But I have taken a look at one of the species that I was planning to study for Olduvai Gorge so far, and that's Antidorcas recki, which is an animal that has an adaptation similar to impala based on other reconstructions.  And it is a little bit smaller.  It's more like a Thomson's gazelle, if you've ever seen one of those.  Petite but it seems to be a browser/grazer like impala. 

 So it changes its diet a little bit in the wet season versus the dry season.  And I have a small sample from both FLK Zinj and FLK North, and unfortunately that is standard for archaeological samples.  They're small.  And fortunately there are statistical methods for handling that.  I'm playing around with them still, but, for now, here are my results.  What they mean is that wet and dry season impala and FLK North and FLK Zinj and Antidorcas recki all overlap for heterogeneity.  And then when I parcel out just the Antidorcas recki, these fossil animals from FLK Zinj and FLK North, what I see is that they almost overlap perfectly.   What does this mean? FLK Zinj, right, is the site where hominins were collecting, eating meat from these animals.  FLK North is where carnivores were operating.   I cannot statistically distinguish between them, which seems to indicate that hominins were operating at the same time of the year as the carnivores. 

 Moreover, when I compare them to the impala, it seems that they were operating year round based on those values.   This is really interesting to me because what it means is hominins not only just entered this meat eating niche, increased meat eating niche, but they aren't offsetting that meat eating to avoid carnivores, at least not seasonally, which they have the option of doing as omnivores.   They're facing them head-on...   which makes this reconstruction a little bit more plausible.   This is something that archaeologists and paleoanthropologists argue a lot about.   Many of them do not agree that hominins were hunting, which is why I've deliberately avoided that term and have used only meat eating.  We know that they were meat eating because we know that they were getting meat from these skeletons.  But beyond that, very few people are willing to stake...   their reputations on the idea that hominins were indeed hunting animals and facing down carnivores.  I, too, will not stake my reputation on the idea that they are hunting yet. 

 But I think we have good evidence in support of that, some of which, well, most of which I've not talked about here.  Now, the idea that they were doing this at the same time as carnivores on the ground adds a little more to that story that I think is a valuable new insight into hominin activities, hominin foraging, and hominins entering this new niche.   All right, so I'm circling all the way back around to Homo naledi now.   Where does Homo naledi fit into this story of early Homo evolution?  And I'm going to step aside for one moment to talk about something that was so incredibly wonderful about my experience as a member of this team.   We were able to participate in outreach from day one.  This was an open access endeavor, which meant that as we were discovering these new fossils, we were able to share them immediately.  We would go down into the cave for seven hours, come out, and that evening Skype with students from Taiwan or California.  And I think that just really emphasizes how important it is to have this open access approach.  And I think a lot of paleoanthropologists are turning towards that direction now because it enables us to communicate not only with our colleagues but also with other members of the community.  And this is the human community. 

 That's what we're talking about here.  So I just wanted to put that plug in for the idea of open access and outreach in paleoanthropology.  It's been such an incredibly wonderful experience for me.  So that was a minor detour I just felt like including there.   As you know, we named a new species Homo naledi.   Why is it a new species? This is the first question we always get.  What makes this a new species? There aren't very many things about it that are truly unique, although there are several.  But what makes this a new species is how consistent it is across all 15 individuals.  What we've got here is a very small brained hominin.  The size of about an orange. 

 So it's really not much larger brained than an ape.  But its skull is more like Homo erectus than it is like australopithecines.   That means it has that more gracile or delicate facial and cranial architecture.  It's got very australopithecine-like shoulders.  It's got very curved fingers.  It's also very primitive looking.  And it has a flaring pelvis, which is not something that we've associated with Homo erectus before.   It also has a cone-shaped ribcage.  Both of those things together indicate that it had a larger gut system than what we usually think of as Homo.   But in most other respects it is strikingly modern. 

  It has that precision grip and wrist morphology that looks very derived in the direction of ourselves.  It's got a foot that is almost indistinguishable from our own.   And it has lower limbs that are very long relative to its arms and also relative to their breadth.  They're really long and skinny.   So, when I participated in trying to describe this, in describing this hominin, I mostly focused on the teeth.  I think the teeth are great.  I loved seeing them gleaming in the bottom of the cave.  They're like little pearls down there.  And so it was really, really wonderful to be inviting back to work on the workshop as an early career scientist.   And then to see all my little babies again. 

  And the teeth really are stunningly gorgeous.  I had a discussion with somebody about whether there were cavities.  No, their teeth are so much better than ours.  They are, yeah, they're perfect.  They do get worn rather quickly though.  So that's one great reason to go see a dentist.  (laughs)  One of the things that I looked at with the teeth was this pattern that we've seen changing across australopithecines and Homo, and it's one that we don't necessarily understand functionally.  In fact, may not be functional.  But it is, nevertheless, a pattern that distinguishes Homo from australopithecines.   So, it's the relative size of the paracone versus the metacone. 

 And I just so happen to have an image up here that shows a relatively larger metacone than paracone, but, please take my word for it, in Homo the paracone gets larger than the metacone.   In australopithecines the metacone is larger than the paracone.  And in Homo naledi, it's right in between there.  It's right crossing over into Homo.  And what we do see is that only members of the genus Homo sometimes have metacones that are larger than paracones.  So that's a good reason to be including Homo naledi as it transitions over to the paracone larger than metacone pattern.  And like I said we're not sure what this means functionally, if anything, but it is a pattern that argues for including this species into our own genus.  But coming up I have a few more things I'm a little bit more excited to be participating in.  The blue slab on the left there is the front surface really zoomed in of the front incisors of one of Homo naledi's teeth.  What you're looking at there are incremental growth lines called perikymata, and when we look at these, we can start to estimate the rate of development of this hominin. 

 One of the things that's really fascinating about modern people is that we have this long childhood.  This something we don't see in our closest relatives, and there are a lot of hypotheses for why this long childhood exists.  Many of them revolving around the idea that we have a really long time in which we need to learn all of the skills necessary for being an adult.  And that prolonged childhood of increased brain growth and slower somatic or body growth is the time that allows for that learning.  And it's also something that we can see reflected in the teeth.  How slowly do the teeth develop? How slowly do they emerge? And by linking up those perikymata throughout the dental sequence, we can see how long it takes for them to mature to adulthood.  So I'll be participating in a study on that in the next year that I am really excited to be a part of.  The other thing that might look familiar, that's more dental microwear analysis.  So, because I was doing that on the previous study of hominin prey animals at Olduvai, I was invited to participate in studying Homo naledi's dental microwear as well.  So I don't know what we can tell you about that yet. 

 It hasn't started, but it will tell us something about Homo naledi's diet, which is particularly interesting given these, I never told you.  These are small teeth.  These are relatively small teeth.  But, like I said, it has a large gut.  So there's something very interesting going on with its diet that we have yet to see before.   So I'm arguing that it's Homo, and yet it has this really tiny brain.   What does this mean, especially in light of this behavioral reconstruction that you might be aware of? The idea that Homo naledi is in the bottom of the Dinaledi chamber because living members deliberately put their dead there.   This is really controversial, as you might have guessed.   And we've arrived at this hypothesis not by hoping for it, but because none of the other hypotheses that we could put forward for a hominin, 15 hominins, being the bottom of a cave, all of them were rejected.   And here's why. 

  So we've got at least 15 individuals.  We have all different ages.   And well represented at all different ages.  Multiple neonates, multiple individuals that look, if they were living people, to be between five and 10.  We've got early teens.  We've got late teens.  We've got young adults, and we've got old adults.   From the geological analysis and the sedimentological analysis of the Dinaledi chamber, it appears that they entered at different times.  At least two different times.   There are no other animals in that cave. 

 Now, that's not entirely true because there is an owl that flew in there rather recently, but it is unrelated to that sample, which we know because those bones are preserved very differently.   We have not found a single carnivore mark on any of the hominin bones.   We have no cultural evidence.  There are no stone tools in there.  There's no evidence of fire.  It doesn't look like they were living in there.  We have no suggestion that that would be the case.  They're deep in the dark zone.  There was never any daylight in that area.   And there were never any other entrances once you get as far in as Dragon's Back. 

 That was the way they had to get there.   So, all of this evidence argues against the fact that they wandered in there and got lost because they would have had to do it multiple times.  And I'm telling you this is not an easy place to get to.   It argues against the idea that this was a carnivore accumulation like you see in most of South African hominin sites.   If it were, there would be gnaw marks.  There would also be other animals there.   It argues against this being a flash flood that washed hominins in.  Again, we would see other animals.  We would also see sedimentological particles that would be larger than what we've got in there.  Everything inside is really fine. 

  And there are other hypotheses we could talk about, none of which at this point are quite as strong as the idea, I think, that hominins were putting their dead there.   Now, that's still just a hypothesis, but it kind of ties into a lot of the other findings that I've had that we've kind of underestimated early Homo.  That there's a lot that they are capable of, if you ask the questions in a different way.   So we'll keep asking questions about Homo naledi.   And like I said I think we've set the bar a little too low.   In the future, what I'd really like to do now that I've seen the sort of different traditions of paleoanthropology in eastern and southern Africa is to start to link these up.  There's really no reason why hominins were not traveling between southern and eastern Africa, at least in terms of distance.  So what I want to do is start asking questions about the ecological facilitators or inhibitors to that kind of migration because we do see that there are different biomes in southern and eastern Africa and we see that hominins seem to have been adapting in different directions.   Why? So one of the first things I'm hoping to do to answer some of those questions is to move to a site called Isimila which you may have heard of.  It's a site that has just gobs and gobs of Acheulean hand axes, which are the sort of the Swiss Army Knife of the Paleolithic. 

  And this site is actually right on the edge of both southern and eastern biomes.  So I think it'll begin to start allowing me to ask those questions.  What were the challenges of these different regions, and were hominins able to move back and forth between them?  And, with that, I'd like to say thank you for listening.  I really appreciate the opportunity to talk.  (applause)