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The Behavioral and Biological Origins of Modern Humans

Three Distinct Human Populations

If you've been following what I've said to this point, Homo ergaster is the species that would have left Africa for the first time. I've got it going to the Far East here at just before a million years ago, where it evolved into creatures that we call Homo erectus. Chinese Homo erectus is best known by the Beijing people whom I mentioned a moment ago. So look upon this right hand branch here as the branch that comes out of Homo ergaster and eventually ends up as non-modern humans in the Far East. Then, in Africa it eventually evolves into Homo sapiens, whereas in Europe it evolves into Homo neanderthalensis, the Neanderthals. I'm actually separating Neanderthals at the species level. I don't know whether, I suspect that the Neanderthals could have inter-bred with living humans or with anybody else who lived at the same time. I doubt that genetic divergence was to that degree. I'm just saying they didn't and I think they didn't because if nothing else, even if they met modern humans, there was a behavioral gulf, that one side probably wouldn't have been interested. There certainly is no fossil record, no fossil evidence, for interbreeding.

I have the Neanderthal line coming off later here than I do the Homo erectus line. That's because the oldest evidence that I can see, secure evidence for human presence in Europe is only about a half a million years. Arguably, half a million years, people who lived in Europe and people who lived in Africa sort of still looked alike. Maybe they shared a common ancestor of a half million years. That is, Neanderthals and Homo sapiens--us--may still have shared a common ancestor at a half a million years after Homo erectus had split off. If you accept that then this common ancestry can be called Homo heidelbergensus after a fossil that was found near Heidelberg, Germany and is about half a million years old.

This separate part of the diagram which illustrates my particular perspective on human evolution, the recent "Out of Africa" theory, with three separate species arising out of Homo ergaster , only one of which survived to the present, Homo sapiens, and it caused the extinction of these other two, Homo neanderthalensis and Homo erectus. If you've been following what I've said so far, you may be thinking, OK, you said that you've had modern humans or people who look pretty modern in Africa by 100,000 to 130,000 years ago and that's the fossil evidence behind the recent "Out of Africa" hypothesis, but that they only spread from Africa about 50,000 years ago. What took so long? Why that long lag, 80,000 years? I'd like to say a word or two about that because that's what I study and I think it's a very interesting question to address. There are two answers as to why it took 80,000 for people to spread from Africa--modern people, Homo sapiens--to spread from Africa and replace the Neanderthals and Homo erectus.

One answer, at one level, it's a very easy question to answer. When we look at the people who lived in Africa 130,000 years ago, sure, physically they're quite different from the Neanderthals and they're different in the direction of ourselves. But behaviorally they were not at all different from the Neanderthals. They made the same kinds of crude tools that the Neanderthals did.
Attributes of Fully Modern Behavior First Detectable 50,000-40,000 Years Ago
  • Sharp increase in the diversity and standardization of artifact types

  • First shaped bone, antler, ivory, and shell artifacts ("points," "needles," "awls", etc.)

  • Earliest indisputable art

  • Oldest structured camp floors, including elaborate hearths and the first "ruins"

  • First long-distance transport of large quantities of stone for flaking

  • Oldest ceremony or ritual, expressed both in art and in graves

  • First adaptation to subarctic and arctic climates

  • Major economic advances, including first fishing

  • First population densities approaching those of historic hunter-gatherers in comparable environments
Other things they shared with the Neanderthals is a failure to make art. What this slide in fact shows you is a whole series of behavioral items that are detectable in the archeological record that only appear about 50,000 years ago. It doesn't matter where you are before 50,000 years ago, everybody is behaving in a Neanderthal way. But at 50,000 years ago we get a sharp increase in the diversity of different kind of artifact types. We can now begin to classify them into different pieces the way that archaeologists really like to do. They're more standardized. People beginning 50,000 years ago made tools, specific tools, for specific purposes unlike the Neanderthals or anybody else who lived before 50,000 years ago.

Something else, here's the art thing. The earliest indisputable art shows up at about 50,000 years ago. Something else which is tied to the art thing which is right above it on the slide here is we get the first evidence for the recognition of bone and shell and ivory, plastic raw materials, as stuff you can make artifacts from--they'd already been making stone tools. But it's at 50,000 years ago that bone appeared as a raw material for making artifacts, coins, needles, awls, things of that sort. It's remarkable that before 50,000 years ago people didn't recognize bone. They brought lots of bones back to their sites, presumably their food debris, but they never made artifacts from them. I mentioned that this is connected to the art thing because the earliest art we have is in bone and ivory, shell and things of that sort. I should say too, and a very important point here, that the earliest bone artifacts and the earliest art appear in Africa close to 50,000 years ago, appear in Europe only perhaps 3,000 or 4,000 years later. So again, that would be support for the "Out of Africa" hypothesis.

There are a whole bunch of other things here which I don't really want to go into in detail. There's one, however, that I think is very important, the second to the last one that I have on the screen here. At 50,000 years ago we get evidence for a major advance in human ability to take energy out of nature and build into people, an advance in hunting gathering ability. Everybody until 12,000 or 10,000 years ago was a hunter gatherer, making a living by hunting wild animals, gathering wild resources. But at 50,000 years ago we get a real inflection point, a kind of quantum advance in the ability to hunt and gather. We get the first evidence for fishing, for example. I worked in Southern Africa, I worked at sites that are older than 50,000 and sites that are younger. They're often located right on the coast. They were located on the coast when they were occupied by early people. If you have a site that's older than 50,000 years that was located on the coast, there are no fish bones in it. You can predict that in advance. After 50,000 years, fish will dominate.

It's pretty remarkable to think of people standing on a coastline looking out there, probably seeing fish all the time and not catching them. It's a major source of protein, a major resource that's immediately available to you. What were people doing before 50,000 years ago that caused them to ignore that? Well, when we get into the artifacts it's obvious: they didn't have the technology for fishing. That only appeared after 50,000 years ago. Once you have it, of course, then you're able to exploit this resource. What does it mean? Among other things, there are going to be a lot more people because you're now able to extract energy, calories and other things, out of nature, build them into populations and increase your population density.

One of the things that's obvious, I have that here, it's the last item. After 50,000 years ago, people were much more numerous on the ground than they were before under comparable environmental circumstances. One of the reasons that the Cro-Magnons were able to replace the Neanderthals so quickly is that when they appeared in Europe, they were much more abundant than the Neanderthals who they confronted. They were also much better armed, I can show that from the technology, as well.

PaleoArtSuccS.jpg This is just a slide to make some points about the artifacts that I've already made. Here's the 50,000 year mark here. You get the first bone artifacts, art objects including things that were really, maybe I should call jewelry. These are bone pendants. I regard them as art. They're items of personal decoration. Then here's a variety of cultural stages before 50,000 years ago with much simpler artifacts including no bone tools and no art. I should say from this, this is two and a half, of course, when stone tools first appeared, there was some change through time in artifacts between two and a half million years ago and 50,000 years ago. Without getting into the details, that's what this chart is supposed to show you. But the change is very slow. And it seems to have occurred hand in hand with change in morphology. In other words, human form changes pretty slowly between two and a half million and 50,000 years ago and the artifacts change pretty slowly. Then 50,000 years ago what happens? The human form stops changing. We are essentially indistinguishable in any major respect from people who lived 50,000 years ago. But look what's happened to culture.

So something very important happened 50,000 years ago. I think we crossed a kind of Rubicon, a threshold. We are effectively the hardware that allows the running of a vast range of different software programs. I think what happened--I like that analogy because my students can relate to it in a way that they couldn't relate to a lot of things I thought when I was their age--but what I think happened 50,000 years ago was the change in the operating system. This is basically, I think it was a point mutation that effected the brain. It may have been something that allowed languages as we understand it today, rapidly produced, articulate speech, the kind that I'm throwing out at you right now. You may be having a little difficulty because I speak very fast, but you're not having problems where you have to look up each work in a dictionary and then you miss the next ten, right? It's not a difficulty, our minds handle that particular issue without any problem whatsoever. I don't think that the Neanderthals could have.

But I must say that they could have dealt with speech in quite the same way, that they had language in the way we do. But I have to tell you, this is the weakness in my theory, this is the problem that I will refer to as the second kind of answer to why there was an 80,000 year lag between the appearance of people who look sort of like us and their spread. The behavioral change is very obvious and that's what allows the spread. But what lies behind the behavioral change? Well, that's the problem. I think it was a biological change. I think the Neanderthals were differently wired than we are. They could not behave as modern humans and so they became extinct. But I have no real direct fossil evidence for that. Neanderthal skulls are very differently shaped than ours. I'm going to go through some slides very quickly and maybe I'll get to one that shows you that. But it doesn't mean that the brain underneath was differently organized.

When you look at these earlier stages in change in time, in artifacts, in two and a half millions years I mentioned yes, we get the first stone artifacts and the first relatively large brained humans. There's an inflection, an increase in brain size at two and a half million. It's fairly dramatic and you can understand how artifacts would appear in connection with that. At about 1.7 we get another change in artifacts, the first appearance of hand axes and things of that sort and there's also a change, what seems to be a fairly dramatic, sudden change in flexipoint increase in brain size. And there may be another one at about 250,000 years ago, 0.25 million years ago--ny is millions years ago. There may have been another change in increase in brain size at about 250,000 years ago, ushering in yet a somewhat different way of making stone artifacts. But if there was at 250,000 years ago, if there was a change in brain size, it was to the size of modern brains. After 250,000 years ago everybody, including the Neanderthals, had brains at least as large as ours. The Neanderthals on average had somewhat larger brains.

So you can't use brain size as any kind of measure of behavior, behavioral ability, intellectual capacity, whatever word you want to use, after 250,000 years ago. If you're going to talk about a change 50,000 years ago you've got to rely on internal structure. It would have been a change in the organization of the brain. I imagine, for example, there are people in this room that know a lot more about the human brain than I do, but you know that the capacity for language resides in different parts of the brain. There's a part of the brain called brochosario where vocabulary resides--this can be established from unfortunate people who have had accidents that damage their brain--there's a part of the brain where vocabulary resides, there's another part where the structural rules, the grammar resides and so forth. And people who have these parts of their brains damaged, they can remember words, that part remains intact, but they lose their ability to construct sentences if the grammatical part is damaged.

I imagine that what happened 50,000 years ago was a highly advantageous mutation that produced a brain in which these things, these different parts were now very much better wired together, something of that sort. And then we have language as we understand it and this rapid spread from Africa and all the cultural innovations that obviously depended upon language and that allowed this spread from Africa. But I cannot show that in terms of the skulls that we have; they do not reveal the internal structure of the brain. Neanderthal skulls are differently shaped but I can't argue from that that they function differently from ours. So in that sense, my idea about a mutation, I think it's the most economic one available to us but it's not a great scientific hypothesis because at the moment it can't be falsified.

I just thought I'd show you some slides quickly to back up some of my points. These are some of the bone artifacts that people made beginning 40,000 to 50,000 years ago. You see this thing up on the top here. The top one has got a hole on the end. What is it? It's a needle, obviously, right. And that's surely what it was. We have the first evidence for tailored clothing after 50,000 years ago. One of the things that the Cro-Magnons could do that the Neanderthals couldn't was to live in arctic environments. How did they do that? Well, they made much nicer houses, much better houses than Neanderthals did but they also made tailored clothing and here's some of the evidence for it.

But we actually have even better evidence. We have soil traces of clothing around graves that date to 35,000 to 40,000 years ago that are obviously--with Cro-Magnon skeletons--obviously indications of clothing. Here's some other bone artifacts that appeared at about 40,000 to 50,000 years ago. We can't always understand exactly what these things were used for but I think they're obvious enough as artifacts. There are these things. This is art made again in bone or in this case, in ivory. Female figurines. Nothing like this before 40-50,000 years ago.

Maybe I can go back to something I said at the beginning in talking about this. I was on this stage a couple of years ago talking to an audience in a symposium on the origins of art. I said look, the Neanderthals didn't make it, it appears very suddenly. It's kind of a creative explosion between roughly 45,000 years ago and suddenly there's art everywhere. I said, I think they didn't make art because they were genetically incapable of it, if you like, intellectually incapable of it as a result of the way in which they were wired together. It did not meet with a lot of enthusiasm in the part of the audience, most of whom were social anthropologists and their students. The person who got up after me said, well, he didn't believe that. And there was actual applause from the audience. I'm thinking, what's going on here? So I asked some people afterwards and it turned out that this is an affirmative action issue. It's as if I was trying to keep the Neanderthals out of college. When I said, what is your evidence that they produced art? Well, there's no evidence that they produced art but they could have. I was thinking to myself, if that's the kind of arguments you want to make, then there's no point in doing a study like this. I was sitting there thinking, gee, I can imagine some two inch long Mesozoic mammal trying to make up his mind whether to keep his blood warm or paint the Mona Lisa.

Of course, we have this, everybody is familiar with that kind of thing. I talked about housing. You may have seen on a slide that I had before that one of the innovations, one of the novelties that appears 50,000 years ago is better housing. This is a house that was occupied in the Ukraine in this Cro-Magnon interval made of mammoth bones. That's the way, the upper left, is what it looked like when it was first executed, all the bones sort of falling in. Underneath were bunches of artifacts and broken up smaller animal bones that are food debris. That's an artist's reconstruction of what the thing probably looked like. This is in an area where the Neanderthal couldn't even live, it was too cold for them but you can understand how the Cro-Magnons were able to do that with that kind of housing.

Here again, back to this question of living in areas where the Neanderthals couldn't live, here's some people, Cro-Magnons, trapping for fur, arctic fox in this case. We actually have evidence that this happened. We have sites where the animals that are represented are mainly arctic fox or wolf and all we have are the paws, or the paw bones, that is. The skins have long since disappeared but the paws are what would have been removed with the skins. And we have sites where there are thousands of these things. People were obviously trapping for furs but only the Cro-Magnons did that, the Neanderthals didn't. We have no evidence for that and of course they didn't live in areas where Cro-Magnons were able to live as a result of using these furs.

Elaborate burials appear only about 40,000 to 50,000 years ago. This is one reconstructed from an actual excavation in the Czech Republic. SLIDE # 14 We had other things which I only barely alluded to. The expansions of human populations, I said that the Cro-Magnons were able to live in environments where the Neanderthals couldn't. And among those environments were very cold places like Siberia. Of course, until you get people to Siberia which is at the upper left hand corner of this slide, you can't get them into the Americas. And that's what this slide is designed to show. It's got some other points, too but the occupation of the Americas obviously could not occur until we have the evolution of the Cro-Magnons. In fact, we don't actually get people living up in the Northeastern corner of Asia, in Northeast Siberia until about 13,000 or 14,000 years ago. So even the Cro-Magnons took a little while to adapt to the most rigorous environments that were available on the earth. Once they were up there then they had a chance of making it into the Americas.

Australia is another place that's interesting in this context. As far as I'm concerned, there's no good evidence for occupation of Australia before about 40,000 years ago. Australia is very different then the American situation we were just talking about a moment ago. If you were to come across, if you were to come to America 10 or 12 or 13,000 years ago, as I believe people first did, you could have actually walked across on dry land because the Bering Straits were emerging, there was a lot of water locked up in the glaciers and that lowered sea levels sufficiently for the Bering Straits to become dry land. You could walk right across from Asia. You could have done the same thing to Australia, all we needed were boats. Even with lower sea levels there were always substantial stretches of sea to cross. So the first Australians had to come with boats. And they had these pretty good boats because they always had to be able to get across at least 50 miles of open sea. You couldn't have something that would get water logged and sink. To me it's no mystery that the first Australians only got there 40,000 years ago because I don't think people before that were able to intellectually to construct the kinds of boats necessary to make the trip.

This is the last point here and I'll be quiet. There's a reconstruction of a Neanderthal skull on the left and a Cro-Magnon skull, in fact the Cro-Magnon skull, the original Old Man so-called of Cro-Magnon on the right. You can see a couple things here. First of all, you can see there's a very similar size in terms of their brain case, the part that encloses the brain. But you can also see they're very different in shape. I'm not just talking about the face, Neanderthals have really strange faces. As I say, if one walked into this room right now you'd have no difficulty detecting him. It's as if you put your fingers on your nose and pulled out two inches, everything swept back from there. So their faces are very different but you can see the skull is also differently shaped. In fact, if you were to make measurements, let's say from between the root of the nose back to the rear of the skull, the Neanderthal one would be very long compared to the Cro-Magnon one, particularly if you compared that measurement to a measurement from the ear aperture to the top. Neanderthal skulls were kind of long and low compared to ours which are shorter and higher. But unfortunately, even with this difference in shape, I can't say that that tells you anything about the difference in the way the brains were organized inside. This is, as I said, a major problem with my notion as to what actually lays ultimately behind this spread of Africans to Eurasia, "Out of Africa" to Eurasia 50,000 years ago. Thank you very much.


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