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The Behavioral and Biological Origins of Modern Humans


If you're listening today, I heard Jeannie of course, to begin with, talking about creationism and evolution. I suspect that people who are teaching in high schools are very much familiar with that particular problem and whether or not you're even allowed to talk about evolution or whether you're supposed to present creationism alongside it or whatever.

Something that you might not be so aware of is what's happening in universities, at least in anthropology, problems like mine. I don't know whether it's an interesting thing or not. It's very much in the top of my mind because I encounter it on a kind of daily basis. Obviously, there's no problem with creationists. There's the occasional student who will come up and ask you how you reconcile what you're telling him about human evolution with their religious beliefs. It's usually not an antagonistic question. They are really genuinely interested in whether you can be helpful or not. They don't leave your office feeling hostile. But a much bigger problem is with your colleagues within the department. Because in many anthropology departments now the majority of people are what are called radical multiculturalists or post modernists. Their basic perspective is that there's no truth, no objective reality.

So, when you're studying evolution, all you're doing is making up a story about the past. Which is essentially indistinguishable from any number of other stories which have been recorded through the ages, including of course, the Book of Genesis. Not that they're pushing the Book of Genesis or any other particular story over your's, they're just saying that your particular way of looking at the past, your particular way of reconstructing human evolution, is not preferable to any number of other ways which come out of different ethnic groups. It's a very difficult thing to live with; to me it's bizarre, it's just absolutely absurd. What they would tell you is that Western medicine is just another way of looking at illness. The germ theory of disease is no different from a theory that's based on witchcraft or whatever. Of course, when they get sick, they go to a doctor. So immediately the hypocrisy shows up. But when making a choice like that, they say they were basically making a political choice, that they themselves have been brainwashed into a particular perspective. Anyway, just wanted to get that off my chest.

Now, I'm going to take it for granted here today that everybody is prepared to accept the idea that humans have evolved. And not only that but that you're prepared to accept the idea that there's a methodology, a scientific methodology, for actually tracing the path of human evolution. That you can point at ideas about what's happened in the past, particularly with regards to where humans have come from and you can go out and test those ideas or at least falsify some and thereby hopefully make it more likely that others are true.

Now, this gets me to another question which--and I don't mean to be facetious about this--but it does bother me a lot in a strictly personal sense. And that's this idea of how we know what we know. When I was a graduate student a long time ago, you just sort of knew because you stumbled across the truth and there it was. And we now recognize that you've got to be a little bit more careful in that. In fact, there is some kind of kernel of truth to the post modernist critique that your upbringing, even maybe your ethnicity, certainly your gender do bias you in certain ways in terms of how you're going to look at the past. And you have to be careful to try and expose these biases to the extent that you can. I accept that and I try my best and I'll try that as I present what I'm going to talk to you about this afternoon. I'll try and ensure as best I can that I am not allowing my own preconceptions to color my presentation to an extent where you wouldn't be able to pull my biases apart from what I'm going to have to say.

But another issue that I think is even more critical has to do with the nature of evidence, the nature of argumentation, the rules of argumentation. Now, what I'm going to talk about today is where modern humans came from, where people who look like us came from. When I say look like, I mean people who would not create any excitement if they were sitting in the room with you today. As recently as 40,000 or 50,000 years ago, there were plenty of people around who in fact would generate a lot of attention if they were to enter at this very moment. The best known of those people are the people we call the Neanderthals. People who lived in Europe beginning at least 200,000 years ago and who disappeared from Europe about 40,000 or 50,000 years ago. I'm going to argue to you that they disappeared by being overrun, in effect. They were extinguished when modern people, the people we often call the Cro-Magnons, entered Europe, ultimately from Africa and essentially caused the Neanderthals, their population to dwindle and eventually to become extinct all together without having passed on any genes or at least any significant number of genes, to living Europeans.

When I first entered anthropology 35 years ago, I didn't have an opinion on this. I'd heard about the Neanderthals, I was fascinated by them, I wanted to study them. I went to graduate school. In fact, I went to work at the University of Chicago with a person who some people in here may know, he eventually moved to the University of California at Berkeley, Professor Clark Howell, and recently retired although he's still very active there as an emeritus professor. He was a specialist on the Neanderthals at the time and I went to work with him. He said you couldn't really do the kind of thing I wanted to do by studying in Chicago, I had to go off to France where there were, in fact, at some time in the past Neanderthals, and where you could actually get access to the bones and the artifacts.

I was very fortunate. I went off the University of Bordeaux to work with an archeologist there who was interested in the behavior of the Neanderthals. He took me out to see a lot of these sites that the Neanderthals had occupied and had then been occupied by the Cro-Magnons just afterwards. And it turned out that just afterwards--was the operative term--that you had the Neanderthal layers building up in these caves. That's mainly what the kinds of sites they were. And then right on top of them were the Cro-Magnon layers without any indication that there had been any time that had passed between the Neanderthal and the Cro-Magnon occupations of these sites. We now know that the time between the Neanderthal extinction and the appearance of Cro-Magnons is irresolvable as far as we can date it. It occurred between 40,000 and 50,000 years ago, maybe a little earlier on the east of Europe than on the west, which would make sense if in fact the Cro-Magnons entered from the east coming from Africa and then moved westward.

In any case, it occurred almost instantaneously from a geologic perspective. And this is very obvious when you look into these cave sites and you see that there are no intermediate levels; the Neanderthals were there one day, at least from a geologic perspective, and the Cro-Magnons were there the next. That impressed me a lot. I thought, how could it be, how could anybody argue then that the Neanderthals had evolved into the Cro-Magnons based just what I could see in this case. There was other evidence too that I found very impressive. Of course, there was the fossils and I'd known about those. Neanderthals are very different looking people--or were--and I'll show you a picture or two to illustrate this later on. It seemed to me that they were too different to argue that they could have evolved into Cro-Magnons or people like ourselves--we are Cro-Magnons--so people like ourselves, within a very short period of time. It couldn't have been more than a few centuries at the very most between the time of the last Neanderthals and the time of the first Cro-Magnons, at least in France where I was looking.

I thought well, that's additional evidence that they must have just disappeared and had been replaced by the Cro-Magnons. But I also looked at the stone tools. The stone tools were very interesting to me. The Neanderthal stone tools I couldn't sort nicely into types. That's what archaeologists like to do, isn't it. If you think that, it's true. Archaeologists go out and they dig up a bunch of stuff be it pot shards or in the case of the Neanderthals it would be stone artifacts, put them on a table and then you've got all these pigeonholes, these different kinds of stone artifacts that you somehow imagined in your mind and now you're putting all the Neanderthal artifacts into different pigeonholes, classifying them.

Well, I was trying this with the Neanderthal artifacts. I couldn't do it. My professor in France who was the world's living authority on this and who had actually made up the classification scheme couldn't do it much better than I could. A lot of the artifacts fell between the cracks, they didn't fit into nice pigeonholes. It was as if when the Neanderthals went to make a stone tool they weren't really concerned about its final form as you or I might perceive it, they were interested in an edge or a point or something of that sort. And it made it very difficult to do this kind of classificatory exercise.

But when you got to the Cro-Magnons it was a different story. It was like they went to the hardware store and they bought pliers and saws and whatever. Of course, they weren't literally buying them, they were manufacturing them. But they had a specific metal template in mind of each individual tool. They were making specific tools for specific purposes. When I saw that I thought gee, the Neanderthals were very different in their mindsets than I am. The Cro-Magnons were like me. Again, let me remind you that the replacement, if you want to call it that, whatever term you want to use, the time between the last of the Neanderthals and the first of the Cro-Magnons was very, very brief, on the order of say centuries, maybe a millennium at the very outside. So I was convinced more than 30 years ago the Neanderthals were extinct, that they had disappeared without issue, that they had been replaced by people coming from somewhere else.

Now what's happened in the intermediate 30 years? Well, as I'm going to tell you in a little bit, we know where they came from now, the Cro-Magnons, they came from Africa. And that's a new discovery. We didn't know that 30 years ago but the fossil record now indicates that very clearly. What else have we discovered? We've discovered some very interesting things about the evolution of the Neanderthal. We know that they in fact evolved exclusively in Europe, beginning perhaps 400,000 years ago when we can first perceive people who look sort of like them, and that their features didn't appear as a kind of integrated complex. You don't get people who are sort of not Neanderthal and then a little more Neanderthal and a little more and a little more and then eventually fully Neanderthal. What you get are people who show strange mixes of what are classically Neanderthal features. 300,000 years ago they had features of the brow or the face of the Neanderthal but not features of the back of the skull. And in fact in different places they will show different combinations of features. In some places they look Neanderthal 300,000 years ago in the face, in other places they look Neanderthal in the back of the skull but they still have non-Neanderthal faces.

Well, this is something, as I say, that we've only learned recently. To me, it suggest that the Neanderthals evolved mainly through what we call gene drift, through random chance, through random accumulation of genetic change rather than through natural selection. That the peculiarities of the Neanderthal face and the Neanderthal skull and many of the peculiarities of the body are not a result of natural selection, they're a result of chance change in what were obviously very small isolated populations.

You say, what's the meaning of that? Among other things it means that Neanderthal morphology could not have been changed very quickly by simply giving them different tools, by saying well gee, you people have evolved in this particular way because you're using your teeth in some strange way, it's a natural selective thing. It wasn't like that. They evolved, perhaps largely, through sexual selection, something of that sort, and became very peculiar looking not because they were adapting in their teeth or something of that sort to particular environmental or cultural circumstances. And it means that if you'd given Neanderthals Cro-Magnon tools 40,000 years ago, I don't think they would have become Cro-Magnons immediately, just as a result of doing things differently now with different tools.

You can argue that from another perspective. We have Neanderthal kids including ones down to below two years and they already show classic Neanderthal features. Which again suggests these things are wired in, they're not things you can simply change, they're not plastic to be changed by the addition of different tools. We have learned, we got additional evidence to suggest that Neanderthals could not have changed overnight into the Cro-Magnon. And then of course, other things, including something we've touched on, I've heard touched on in other lectures, is the advent of genetic research that bears directly on human evolution. In particular this past summer, I'm sure many people saw in the newspapers that a laboratory in Munich had succeeded in isolating DNA from a Neanderthal bone. In fact, from the original Neanderthal, the humerus or upper arm bone of the original Neanderthal. It was mitochondrial DNA and it was very divergent from the DNA, mitochondrial DNA, of anybody alive today. Again, it would suggest that Neanderthals are an extinct side branch of humanity.

We've learned a lot of things. To me, what we've learned though is only added to what I already believe 30 years ago. And yet--and here's my basic point--there are still people out there who believe that the Neanderthals are directly ancestral to modern humans. Why would they believe that? The problem is you can never have too much negative evidence. If you want to argue that, and in particular, if every time something new comes up with regard to the Neanderthals, you want the New York Times to call you up and ask you about it, take the opposite position, take the Devil's advocate position. But to me, the issue has been decided.

This gets to the question of how, what do I mean when I say it's decided. To me, this kind of study is kind of like a jury trial. It's a jury trial where you're basically the jury, I'm kind of an advocate, we could have somebody up here I suppose who would argue that the Neanderthals in fact are not extinct, that they directly evolved into modern Europeans. And they would be an advocate for the other side. Whether who's prosecution or who's defense doesn't matter. We could maybe think of it as a civil case with people arguing and you're the jury and you've got to make some kind of decision. But it's not science in the sense that you can do it in a physics lab or it's not science in the sense of the way in which you would decide whether the earth goes around the sun or the sun goes around the earth. That can be decided pretty conclusively and we move on. Although, there are people in my department who probably think that's a political decision. I think we would agree that that's something that you can in fact decide and forget. There's real closure on that where you can't reach closure on the question of what happened to the Neanderthals in the same way. And you have to accept that it is something like a judicial proceeding. And the difference, if there is one, between studying the Neanderthals and what happened to them and, say, the O. J. Simpson case is that we don't actually have to come to a verdict within some set period of time. And it makes it possible for people to continue argue endlessly about these things, even when I think they have been effectively decided.

That's by way of preface. I want to show you a few slides. I don't want to take too much of your time. I've already given you the essence of what I want to say. I believe that modern humans originated in Africa, some time before 50,000 years ago and spread from Africa to replace non-modern humans elsewhere. I'm going to show you some slides that I hope will allow me to expand on this.
Theories of modern human origins
  • Multiregional Evolution

  • Recent African Origin
    (a.k.a. "Out of Africa," "Garden of Eden", "African Eve theory")
There are actually two, if you like, theories of modern human origins; I've already put down one, for better or for worse. That's the one that's called multiregional theory and I'll talk about it a little more. Then there's the one I'm pushing here which is called the recent African origin theory. It's got other names, other aliases: "Out of Africa", "Garden of Eden", the "African Ape Theory". Let me tell you about the multiregional theory first. This is the one I'm effectively telling you is, I think, dead today but there are people who are still advocating it.

Theory of Multiregional Evolution

Theory of Multiregional Evolution
  • human dispersal from Africa to Eurasia by 1 million years ago

  • far-flung human populations then diverge morphologically due to natural selection and gene drift

  • gene flow ensures that highly adaptive novelties (like larger brains) spread everywhere

  • modern humans thus evolve simultaneously in Africa, Europe, and Asia
What this theory postulates is a theory of items which I've listed for you here on the screen. First of all, I'm taking it for granted that everybody is aware that humans in the broad sense originated in Africa exclusively. When I say in the broad sense, I mean bipedal creatures like ourselves who appear in the African fossil record between four and five millions years ago. It will probably ultimately turn out that the first one, the first bipedal humans are five to six millions years old. We don't have the fossils for that to show that yet but you can use genetic evidence to argue that. At five to six millions years ago then we would have shared an ancestor with the chimpanzee. The chimpanzee went its way and we became bipedal and ultimately evolved into what we are today.

Now, humans were constrained to Africa, confined to Africa, until at least two millions years ago and I would argue until probably close to one million. It was only some time between two and one, closer to one perhaps, that they dispersed to Eurasia. So before two million and probably before say 1.2, 1.3, there were no human beings in Eurasia. They arrived there only just before one million, probably, certainly from Africa, probably right in before one million. The multiregional theory postulates that that's in fact more or less accepted paleoanthropological fact right now. The recent African origin theory accepts that as well.

What the multiregional theory says next is that now you have populations spread over much of the globe, living in different environment--this is now one millions years or later--living in very different environments and they begin to diverge through natural selection and gene drift. So they begin to look a little different in different places as with well known evolutionary processes. Here, in the next point, the third point is where the multiregional theory really departs from the recent "Out of Africa" theory. What the multiregional theory says is that even though you have this divergence going on as a result of natural selection and gene drift, that there's gene flow across vast areas of the old world, vast areas of Eurasia and Africa. This ensures that adaptive novelties, what paleontologists might call derived features that are of substantial selective advantage, get past over these vast areas very quickly. The gene flow was maintained between populations that were living in Beijing and Paris, Capetown, wherever human populations were living and that gene flow then proceeded to ensure that adaptive novelty spread and that as a result the degree of divergence was restricted, that these populations never could proceed to the point in different places where they could become different species and that modern humans originated everywhere--Africa but also Europe and Asia--where non-modern humans had lived before.

I've already mentioned that there were non-modern humans in Europe until 50,000 years ago, the people we call the Neanderthals. And what this theory is basically saying is yes, the Neanderthals evolved into modern Europeans, people who lived in Africa at the same time as the Neanderthals evolved into modern Africans and people who were living in the Far East before 50,000 years ago evolved into modern Far Eastern, modern Chinese, modern Indonesians and whatever. This is, as they say, the theory of multiregional evolution. If you're wondering what the evidence for it is, I don't think there is any. The basic evidence has subsided, particularly in the Far East, I should say and not so much, interestingly, in Europe or Africa. But in the Far East, what is supposed to be morphological resemblances between very ancient fossils, let's say the Beijing people who were found near the modern city of Beijing, they date to about 500,000 years ago. We have skulls, we have limb bones. The skulls in particular are said by some people to have features in them that resemble those of the living Chinese. Therefore there must have been continuity between 500,000 years ago and historic times, at least biological continuity.

I don't have time to get into these features but many of them that are cited as indicating continuity in fact were very much more widespread than just in East Asia. I'll mention one. There's a tendency in living East Asians and native Americans who are actually derived from East Asians, for the upper incisor teeth to be curled at the edges and to have a larger biting surface than the incisor teeth in many other living human populations. This curling around of the upper incisors at the edges is called shoveling. And it's true that the Beijing people of a half a million years ago had shoveled incisor teeth. But so did the Neanderthal and nobody is arguing that the Beijing people were ancestral to the Neanderthals.

There are other features that are actually said to indicate continuity between ancient Chinese, 500,000 year old Chinese from modern ones, which are more common outside of China than they are in, today and in the past. And in fact, you can argue as long as you have lots of features to choose from, there are actually more features that you can identify in fossils than there are fossils. You'll always be able to find something that suggests similarity between people at one time and people of another and if you like you can put those people in the same area and say OK, that means there's continuity in a genetic sense, biological continuity between half million year old people and modern people, living people.

I should point out too that with regard to the Chinese case, the Beijing man site, and the as the Beijing man fossils, the five Beijing people fossils of a half a million years ago that are most commonly cited as evidence for continuity between a half a million years ago and the present in China. There's another site on the same place as the original Beijing person site. It's a much later site, it dates to maybe 18,000 years ago. It provided some human skeletons and they've been identified by physical anthropologists, three different skeletons, one a Malayanesian, one an Intuit or Eskimo and one maybe having something to do with the living Chinese. That suggest that there's some problems, isn't there. I'm saying this is by reputable people who have looked at these fossil skeletons. That suggests some problems in making a continuous pattern or a continuous line of evolution between Beijing man people of a half a million years ago and the living Chinese. In fact, I can tell you, the living Chinese, in terms of any racial features if you want to use that term, biological features, skeletal features that distinguish them, appear in China only about 7,000 years ago, however that's to be explained. And in fact, in so far as we can distinguish people skeletally today, one from another and talk about racial features in the skeleton, these are all of very recent origin, within the last 10,000 years. So that kind of evidence for continuity, I just don't see it.


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