>> From the Library of Congress in Washington, DC. ^M00:00:04 ^M00:00:22 >> Tomoko Steen: Welcome, everyone. Today's event is sponsored by the Science, Technology, and Business Division, here at the Library of Congress. I'm Tomoko Steen and this is specialist, here at the Library. And this is one of the Science Literacies. And today's topic is molecular anthropology. Is that right? And genetics. Anthropology, genetics. Today's speaker, Doctor Adam Wilkins. He's a geneticist and author. He has also wrote several books, previously. And he has been trained as a geneticist, especially microbiogenetics [phonetic]. And he has worked on a that, a few of those times. But he turned himself into the more science writing and public outreach. He has been the editor of the ''BioEssays'' [inaudible] journal. As well as, now he is the editor of the Perspective section of the Genetics, which is the probably the leading journal for the field of genetics. And Doctor Wilkins have done PhD at University of Washington. And so, he was born in Columbus, Ohio. But currently, he is at Humboldt University. So, a lot of people ask me, ''Is he a German?'' Surely, he's American, I guess. But it's going to be an interesting talk. And we have a book, outside. So, after this we have a book signing. So, if you are interested, take a look at the book, as well. And before [inaudible], maybe we just invite speaker, Doctor Wilkins. ^M00:02:19 [ Applause ] ^M00:02:23 >> Adam Wilkins: Tamoko, thank you very much, of that introduction. And even more, I'd like to thank you and the Library of Congress for inviting me to come speak. It really is an honor and a privilege to be here. The Library of Congress is a bastion of American civilization and as such, the defender of fundamental American values. And those need defense as much today, as they have at any other time. So, my topic is indeed the evolution of the human face. Or if we were to put it in terms that Rudyard Kipling might like, how our species acquired its face. As background, too. Before I get into the subject itself, I'd just like to say a little bit about how I got interested in it. As Tomoko said, my background is in other things, particularly microbial genetics. But I've always been interested in evolution. And I think it's safe to say that for most of the 20th century, evolutionary biology had a very self-consistent reasonable logical theory. But there is a real lack of specificity to how much one could say about specific evolutionary changes, for which there was evidence. But we could not tie specific genes and genetic factors to particular evolutionary changes. So, in a way it was a kind of. It was a good theory, but it lacked a certain kind of rigor. But beginning in the 1970s and acquiring strength in the 1980s, it began to be possible to isolate genes, specifically. And make very specific hypotheses about what particular genes were doing in evolution. Not the least in how particular genes were responsible for particular traits in different organisms. And for some of the interest in evolution or biology, this is the prospect of scientific heaven. To be able to really have good concrete ideas about what genes might be involved in evolutionary changes of particular kinds. So, I wasn't involved as a laboratory scientist, in this work. But I was very interested in it, and I wrote commentaries. And I finally, wrote a book that summed up the state of the field, which came out in 2002. And shortly after the book became published, I found myself thinking, ''Well, how might this kind of thinking apply to human evolution?'' We are a distinctive looking animal species. We are animals. Of course, we are a lot more. Our species is unique in what it does in the world, and what it has done. But surely, there would be a scope, I felt, for this new branch of evolutionary biology, called evolutionary developmental biology. To say something interesting about humans, human evolution. And surely, after having this thought, I felt, ''Ah, the human face might be a particularly interesting aspect of human characteristics, of human biology, to focus on.'' It was more just a hunch and a feeling. Because at the time, actually there was very little one could say about the genes that are involved in constructing the human face. And that might be involved in the evolutionary series that gave rise to our species, and out particular kind of face. For various reasons, I couldn't start on the book, right away. Having to do with work and other projects. And I didn't really start on it in a serious way until 2011. And it was a good thing that I waited, because in a sense, there was very little known when I first had the idea. By the time I got started on the book, there was a great deal more information. So, in effect, the field had caught up with my ambitions to write about it, which was nice. Okay. So, let us. I'll just add one more thing. That is that in the sense, as I worked on the book I found the focus of my interest changing, somewhat, from that of how the genes that are involved in making the human face. How they'd evolved and how their expression characteristics had changed. More to the why of this. What was it in our evolutionary history, the evolution of our species, that really has made us the species we are? So, while my official title for this talk is ''Making Faces, the Evolutionary Origins of the Human Face'', The alternative title gives more of a hint as to what I'm going to focus on. How our evolving face helped make us human. Okay. So, let us begin with a basic question. What precisely do we mean by the face? Now, we all recognize faces. And even in this sort of caricature of form, that is Clerdia [phonetic] face. But how do we define the face? It's always good to start with a clear definition of one's subject. And briefly, the face is the forward directed part of the animal's head with a mouth and three kinds of sense organs for vision, smell, and taste. Forward directed means the face is set in the direction of movement of the animal. So, our faces do, indeed, look forward toward the environment that the animal is entering. And what I have here, is pictures represented of vertebrates. So, we are in the group of animals termed the vertebrates, which are a subdivision of a major group called the Chordata. We needn't go into those details very much. But the vertebrates, all the animals with backbones, consist of about 50,000 species. Which is roughly a half to one percent of all the estimated existing animal species in the world. Still, 50,000 is a big number. And all vertebrates have faces, as you can see, here. We cannot see the sensor organs very directly, in this, but of course, you can. Well, except for the eyes. So, what we have here, is a fish, an amphibian, a reptile, bird. And two of my favorite mammalian species, wolves and us. And they all have eyes and some sort of visible nostrils for olfaction. We can't see the organs of taste, because they're within the mouth. So, another way of putting this, is to say that the face is the sensory headquarters of the animal. Okay. It's a really concentrated area of the animal's body, that had three of the main kinds of sensor organs. With, of course, the organs of hearing, just behind the face. And they are in close association with the mouth. Now, why is the face constructed this way? Well, we get a clue from considering the evidence that we have on the earliest vertebrates, which were tiny fish. And they did, indeed, have, from everything we know. Of course, we don't know directly about their organs of taste and olfaction. But they had two eyes in association with the mouth. And this must have been, for them, a tremendous aid to being able to find food and to ingest it. To have the eyes and the organs of olfaction near the mouth, helps the animal, of course, to find food. If you imagine the eyes and the organs of olfaction back here, you can see that they wouldn't be nearly as useful to the animal for finding food, as if they were in close association with the mouth. ^M00:10:02 So, having defined the face, let's come to the question of what makes the human face particularly worth talking about? Is it just because it's the face of our species? Quite naturally, we are interested in things that relate directly to us. Just as most of us are more interested in our family and friends, than people down the block, whom we might see most every day. But whom we don't know anything about. So, is the face primarily interesting just because it is our face? Or is it, in fact, something, a rather special and unusual face? And I'm going to argue, briefly, that it is, indeed, a very special and interesting face. So, to answer this question. If you're going to argue there's something special, it's got to be special in comparison to something else. And so, we need to compare it, in this case, with other faces. And let's just focus on the mammals, which is our major subgroup within the vertebrates. So, first of all, let me just admit that there are some very interesting, unusual, indeed special, faces amongst mammals. And we have an assortment of these, here. No need to go into details. You can see, immediately, that they're not like you cat or your dog, which are more typical mammals. But the great majority of mammals actually do have a kind of typical generic face. There are 18 divisions within the mammals, called orders. Okay. It's a taxonomic term. And I've shown here, typical members of eight different orders of mammals. And if I pick the examples from most of the other orders of mammals, it would be a similar picture. The features that the typical mammal has, are a muscle. Okay. Rather well-spaced eyes. Fur on the face. You can see that in all of these. And no real forehead. The head sort of slopes back, gently, from just above the eyes. And those are the features that make for a commonality in the faces of most mammals. And once one has realized that, one sees that, in fact, even amongst some of the oddballs that I showed earlier. Some of them have at least one or two of those common features. And without going into the details, though, just you know, make that point. But having accepted that fact that there is this set of common features. We then come to the rather surprising fact, that one of the most unusual mammalian faces, is that of homo sapiens. That's ourselves. Okay. And since most of us in this room tend to think of the human face as the prototypical, hence, normal face. It may be a surprise to think that we actually have a very odd and different animal face. So, instead of just your taking my word for this claim, that our face is particularly unusual. I decided to quote an authority, here, a man named Donald Enlow. I'm not sure if he's still alive. But he is or was one of the great experts on the craniofacial skeleton. In other words, the skull and the bones of the face. And here, I'll just read out, even though you can read it. I'll read it out. ''The human face is different. Bu ordinary mammalian standards, our facial features are unusual, specialized, and perhaps even grotesque. The long functional muscle that marks the face of most other mammalian forms, is all but lacking in man. The associated snout is reduced to a curious overhanging vestige.'' Known as our nose. ''The face is wide, flat, and vertically disposed.'' Okay. We have these flat, and indeed, vertically disposed faces. ''instead of graceful facial contour sloping back to the skull roof, the human face possesses a unique bulbous, upright forehead in front of an enormous braincase. The flattened face is diminutive in character relative to the remainder of the enlarged head.'' So, our faces are small, relative to that of most other mammals. ''The eyes are close together and they face straight forward. The human dental arches are disproportionately small relative to the size of the whole body.'' In other words, we have smaller teeth. Okay. Indeed, the physical features of our face are unusual. And for an evolutionary biologist, that's interesting. But what makes the human face truly unusual is not its structure, but its behavior. And specifically, its capacity for different expressions, as illustrated here. Okay. Now, there are altogether seven basic strong human expressions. And one is neutral. Okay. Where you're not showing any particular emotion. Anger, disgust, fear, happiness, sadness, and surprise shown in that order, here. The lines under the line drawns, indicate the tension lines from the muscles in the face that create these expressions. I'll have a bit more to say about the facial muscles, in a moment. So, most mammas do not have this great range of expressions, of strong expressions. And certainly, the other vertebrates; fish, amphibians, reptiles, birds, do not have anywhere near this. And I'll come back to the why of that, in a moment. But some of our nearest, and I'm tempted to say dearest relatives, the great apes, in fact do have large expressive capacity. As shown here, in this comparison. And you can make really a very good judgment that the strong expressions they show. Which can often be likened to particular human expressions accompanying certain emotions, really reflect those emotions, because of the context. The chimpanzee happiness expression occurs when the animal is really showing some pleasure in the animals it's interacting with. Or whatever. So, it's not pure anthropomorphism, by a long shot. But these very expressive animals, chimps, bonobos, gorillas a little bit less, orangutans a little bit less. But these very facially expressive animals don't have quite the full range of expressions that we do. And this is just a small illustration of more subtle expressions that our species exhibits. And one of the nice things, is that almost everybody in this audience, and in fact I'm sure everybody in this audience. Can read these expressions and understand something of the emotions that this person is experiencing and displaying in each of these situations. And altogether, there are something like, I don't know the precise number. There are people who study this. This is a whole large area of research. There's something like 50 of these so-called minor expressions. And that's a great number. So, I'm not going to make the claim that we are the most facially expressive animal on earth. Okay. And I stress facially, because other animals really have different ways of expressing their feelings through body language. That is, body language below the head. Through sound and other ways. But facially, we are the most expressive animal on earth. And I say that, not only because of this great range of expressions we have that our nearest animal cousins don't have. And there are scientific ways to measure this, I should add. It's a method called FACS, which we need not go into in detail, here. But by using FACS, you can actually look at the expressions in other animals. And this has been done with chimpanzees and dogs. And they really do by these measurements, by this technique, they really are less expressive than we are, in the range of what they do. But in addition, the frequency of our expressions, I think we are probably the most expressive animal on earth, because we are talking animals. And when we talk to each other, there is a play of expressions on our face. And if you watch any two people having a conversation for any length of time, more than just hello goodbye, you will see this play of expressions as a kind of shadow dialog. And even if you can't hear the words, you can tell something about the feelings that are being expressed accompanying the words. So, this raises an interesting evolutionary question, ''How did we become this super-expressive animal using our faces?'' So, the basic biological foundation of this is a whole set of muscles, called the mimetic muscles, and these are diagrammed, here. And again, we need not go into the details. The key point is that the mimetic muscles are found only in the mammals. And that's why the other vertebrates aren't near as expressive. They don't have the capacity to move their skin on their faces, in the way that we mammals do with these mimetic muscles. The face is the only place on the mammal's body where there's a direct connection to the skin for moving the skin. Okay. And it's a mammalian specialty. Now, other mammals have many of these muscles. Many of the mammals that are not primates don't have the full set. But our nearest relatives do have the full set, the gorillas and the chimpanzees. So, the fact that they are perhaps somewhat less facially expressive, is not due to difference in the muscles. But it must be due to either the way the muscles are innervated or the mental processes that activate the expressions. And I think it's the latter, though in this lecture I won't be able to document this. Just as I won't be able to document many of the things that I say. But I go into them in the book. And of course, we'll be glad to take questions on that, at the end. ^M00:20:05 So, having this whole set of complex muscles isn't the sole explanation for why we're such an expressive species. But these are the elements of our anatomy that make those expressions possible. So, let us now come to the evolutionary questions. And the big one is, or the first big one is, ''What were the major changes that led from fish faces to the human face?'' And as I mentioned, the first fishes evolved around 500 million years, ago. And there is clearly a great deal of difference between this face and this face. Even though they are basic faces by the criteria that I've mentioned. So, let us first look at the general time scale. And then, we're going to home in on this period when the first primates arrived. So, I've spoken of us as mammals. We are, indeed, mammals. But we're within one special group of the mammals, the primates. And the distinctive changes that have evolved in our lineage that have made our face what it is, all arose in this relatively short period. But let's look at the whole period in which animals have existed. So, first of all, the earth is estimated to be 4.5 billion years old, and this is a fairly well-agreed figure. The first animals didn't appear until only 600 million years, ago. So, about the last 12% of the planet's history. These first animals were actually very strange and not easily related to more contemporary mammals. But the first vertebrates and many of the modern kinds of animals originated here, starting about 540 million years, ago. The first vertebrates from their fossils, date to about 500 million years, ago, as I mentioned. The first true mammals, okay, animals that have fur and whose females produce milk for their young, those are the key criteria for making a mammal. Arose in the Jurassic period, the age of dinosaurs. Maybe, 180 to 150 million years, ago. The first primates, which are our mammalian mother group, arose about 60 million years, ago. And we humans arose, our species, arose only 200,000 years, ago. So, if one were to take this whole 600-million-year period for the existence of animals, our species arose. If you were to take that as a 24-hour day, our species arose in the last two minutes. Okay. We are really very recently evolved animals by a number of strong criteria. Okay. We can make that statement with reasonable definitiveness. Now, there were humanlike species, earlier, going back to roughly 2 million years, ago. But that's still only about the last ten minutes of a 24-hour day. Okay. But what we will want to look at now, is how the particular features that make our face special. Some which I enumerated, earlier in that quote from Don Enlow. They all arose during this 60-year period. And specifically. Here, let me backtrack. Let's just look at one early change, which is important. And then, I'll take you through a quick run-through of a lot of evolutionary history. And then, we'll start focusing on the primates. So, the first vertebrates arose about 500 million years, ago. There were further changes. The big change was the evolution of jaws. And here, I'm not talking about the movie star eating shark. But these elements which allow us to chew our food. The evolution of jaws probably happened only once. It was a somewhat unlikely evolutionary event. But it really opened up the capacity of our line of animals to ingest many different kinds of food. Had we remained jawless fish, like this, probably the vertebrates would never have expanded in the way that they or we have. Okay. Now, here is a very quick run-through of vertebrate history that will just take us up to the primates, which is what we're interested in. Because it's within the primates that our distinctive form of face arose. So, about 300 million years, ago, there were lobe finned fish, which were the precursors of the first land dwelling animals, the amphibians. Amphibians gave rise to a number of other land-living forms. In particular, the branch that gave rise to the dinosaurs. And another branch called the Synapsids, which gave rise to the mammals. And indeed, these have been called the mammal-like reptiles. The look very. This is Dimetrodon, a famous early animal, sometimes mistakenly called a dinosaur. It was not. It was a Synapsid. And its key feature, which you can't really see here, that made it mammal-like, was its different dentition. There then, followed further changes in which these more reptilian-looking animals gave rise to mammals. And finally, there were true mammals. The date of true mammals, the first dates are a little bit vague, depending upon what you define as a true mammal. But let's say about 150 million years, ago. Whereas, the modern forms of mammals are more recent than that. And here, just to give you some time sense of when mammalian features started arising. This is Dimetrodon, about 290 million years, ago. This is Cynognathus, an early mammal-like form, only 210 million years, ago. So, about 80 million years. Mammals clearly had their own line of descent. So, a lot of this evolution is summarized in this book. This is the first general account of the evolution of the face, by a man named William K. Gregory, who was a curator at the Museum of Natural History, in New York. And this is his classic book, ''Our Face from Fish to Man''. It was written in the aftermath of the Scopes Trial, the famous trial which had as its issue, the question of whether evolution should be taught in the schools. And this is a famous trial involving famous lawyers, Charles Darrow and William Jennings Bryan, two major figures in American history. So, Gregory wrote this book as a defense of the existence of evolution. And his take-home message was this; ''the basic structure of vertebrate face has stayed much the same, despite many changes in the details. Over 400 million years from the early jawed fish to humans''. And that is, undoubtedly, true. Here we have a fish skull with a fish face and the rest of the skull. Here is a lion skull. And even though, of course, at one level these look very different, in their fundamental structure, they're much the same. So, along with its basic structure, the vertebrate face has retained its central function from fish to man, as sensory headquarters plus the mouth. Despite all the changes in details of structure in numerable species. Okay. So, the organs of smell and taste and vision are much the same in most mammalian faces, in their location and their basic function, as in some of the early vertebrates, which were fish. ^M00:28:16 ^M00:28:22 Okay. So, let's now come to the primates, which is our mother group, in which the distinctive characteristics of the human face arose. And I'm not going to go into the details of mammalian evolution. We're just focusing on the primates. One so-called taxonomic order out of 18. And let us look at the. So, we are primates. And let us look at the earliest primates, from which we arrived. And there are different views. You know, we're trying to reconstruct things that happened roughly 60 to 65 million years, ago. So, there are not living eyewitnesses. So, it involves a matter of scientific reconstruction [inaudible]. And there are different views. From Robert Martin who is one of the great experts on primate evolution, we have this view. From another group, we have something closer to. We have a depiction that is an alternative depiction. In a way, I'm cheating, because this is presumed to be the earliest placental mammal. But the primates arose. Almost certainly arose quickly, as a separate group from something that might have looked like this. So, they might not have looked that different. The important point is that whether you accept this view as closer to the reality of the earliest primate, or this one, these are typical mammalian faces. Okay. As I showed, earlier, where there is a projecting snout, there's fur on the face, and a few other features. ^M00:30:04 So, let us now look at the diversification of the primates and see where the changes came in, that helped to make the human face. And this is a picture of the evolutionary or phylogenetic tree of the primates. And there are two basic groups, called the prosimians and the anthropoid primates. And we are definitely a member of the anthropoid primates. And the split between these two major branches occurred probably around 55, maybe 60 million years, ago. So, the ancestral primates, whether they looked like either of the versions I showed you, were existing at least here. Maybe around 63 million years, ago. And maybe, before. And then, they split into the prosimians and the anthropoid primates. And this is where the first major set of changes that led to the human face took place. And we'll come to the second set of changes, in a moment. But let's look at the first. So, here is a prosimian, which despite some exotic details like the ruff, looks very much like the other mammals that form the majority of mammals. There is a projecting snout, the eyes are very wide apart, there is fur on the face. Here are two anthropoid primates. And all of the so-called anthropoid primates, and we belong to this large division. Anthropoid means man-like. Have these distinguishing features. They have close-set forward-looking eyes. Notice these eyes are definitely more close-set than these. The anthropoid primates have a naked or furless face. And they have a reduced muzzle, compared to the others. So, the net result of this first set of physical changes, which probably took place roughly 50 million years, ago, is that the anthropoid primate face is far more expressive than the prosimian face. Okay. Just by virtue of the face being naked, you can see the skin more clearly in naked faces, than in furred faces. And it is therefore, more expressive of the feelings, intentions, and simple thoughts. Okay. So, this is the first step forward toward a human face. And I think we can see that these faces of the anthropoid primates are, indeed, more humanlike than this, which looks more like a typical mammal. So, the first major set of changes took place roughly 50 million years, ago, changes that led in the direction of the human face. And the second phase of major changes leading to modern human face, including ultimately anatomically modern humans, shown here by this figure. Took place much later. Roughly starting about four to 6 million years, ago. And here, I've just sketched it very crudely. Now, we don't know what the absolutely ancestral hominin, this means the humanlike primates, looked like. But the modern chimpanzee is probably not too far off. There are debates about what the resemblances and differences are. But we can take a modern chimp as a crude representative of the earliest member of the branch that led to humans. And we see some of the changes, here. I'm not going to go into them in detail. But I think you can see that this modern human face, which is a bushman from South Africa. Really is a smaller face than these longer faces of these more apelike humanlike creatures. It's a smaller face, it's flat, it's vertical. There isn't really any sign of a muzzle. Okay. There's a broad forehead. Okay. So, what were the major changes in the second stage? The complete loss of the muzzle in. You know, the complete loss of the muzzle. Flattening and verticalization of the face. So, we really have vertical faces, unlike faces that have projecting snout. The gain of the forehead and behind that, our big brain. And I'm now going to concentrate on this, because it's quite important. One, it really has changed our look as an animal. And secondly, this is connected to the growth of our big brain, which has certainly been a major contributor to the fact that we are such a facially expressive animal. And that those expressions have played a huge part in our evolution a what we are, today. So, one of the driving forces, or one of the trains in our evolution, has been the increasing brain size, shown here fairly diagrammatically. And these are inferred brains, because of course, the brains themselves haven't been preserved. What we have is the skulls. And from the skulls you can reconstruct some of the surface features of the brain. But these are, as I say, somewhat imaginative depictions of the changes in brain size that have occurred in the course of our developing from the first hominins. The first humanlike animals, over roughly, 6 million years. So, what drove the increase in human brain size? This is really an important and interesting question that's fundamental to understanding human evolution. The first key point is that something must have driven this, because brains are expensive. Expensive in terms of energy, hence, in the amount of nutrients that we have to take in. The comprise only about two percent of body weight, which doesn't sound like a large percentage. But it's a relatively large amount for an animal. But they require 20% of the energy needed by the body. Okay. So, brains are energetically expensive. And that makes demands on the animal for adequate nutrition. Okay. So, there are three general explanations. I'm going to run through them fairly quickly and not do any of them real justice. But just to sketch them out. There's the better nutrition hypothesis. The need for greater intelligence for foraging and hunting. And finally, the third hypothesis is that it the growing array of social interactions, something known as the social brain hypothesis, that drove the increase in brain size. So, the better nutrition hypothesis. There are several variants of this. I think one of the favorite ones comes from Richard Wrangham, who is a professor at Harvard, and a friend and colleague of mine. And essentially, is that when humans learned how to cook they were able to increase the efficiency with which they extracted calories from food. And there's a lot of evidence for this. But it's not clear to me that simply having more easier access to more energy would have driven the increase in brain size. I think the more plausible explanation is that there were pressures for increased complexity of behaviors and various brain related functions. Which required better nutrition. But the better nutrition itself, which he has emphasized comes from cooking. And cooking [inaudible] releases more readily available energy. I think that simply the availability of more energy by cooking food, probably does not explain the increase in brain size. And there are other variance of this hypothesis, but they all emphasize increased energy availability from foods as the driving force. So, I think that this is unlikely. I would say it's an insufficient reason to explain the increase in brain size. What about the need for greater intelligence for foraging and hunting? There's no question that foraging and hunting as humans do it, it often more sophisticated, even often a much more sophisticated way of getting food. Than the way most of our brother animals get their food. Including our nearest relatives amongst the primates. So, I think that for various reasons, which I'm not going to detail here. I think that this is unconvincing as the prime driver of what has made our brains bigger. This is unconvincing as the major selective force for larger brains. What about the third one? The growing array of social interactions? The social brain hypothesis. There isn't time to go into all of this, but there is a great deal of support for it. That it was the growing complexity of social interactions, whether in raising offspring, in interacting with each other. That may have been the driving force in driving brain growth. So, in my opinion, this is the best. And it's inextricably bound up with the idea of social selection. Namely, the idea that social interactions strengthen social cohesion. Which promotes the survival of the group, and thereby, of its individual members. ^M00:40:01 And here I've allowed myself to give one reference. This idea has, I think, not really been given enough play. But this idea was first explained by a guy named Herbert Simon, who is an economist, not a biologist. But somebody with a very great range. And the idea simply is that we are necessarily a cooperative species. Certainly, in our early days, we needed a lot of cooperation to get things done. You take the human and put him or her out on his or her own, and that person's survival will be rapidly compromised. We are inherently a social animal and we need our social cohesion, in order to survive. I realize that I'm not giving this argument in its full details and merits, but that's just because of time. But I would recommend if anybody's interested in following it up, looking at this article by Herbert Simon. Now, three key points to that social selection. It's not the same as group selection. Group selection posits that certain things evolved because they were for the good of the group. Instead, the idea of social selection posits that there was strength in social bonds that were a direct benefit to the individual, often at minimal cost. Okay. Again, that deserves more explanation than I can give it, here. But that is a key idea. For humans, the evolution of social interactions must have been, to some degree, coupled with the evolution of language. Okay. It's hard to convey your wish to do things cooperatively without language. You can do it to some extent, and animals do. But language had almost undoubtedly been of crucial importance in our evolution as a species. Finally, the evolution of language was almost certainly tied up with both the evolution of the brain and of facial expressions accompanying speech. But faces, in that last point, we come back to the face. That facial expressions are in speech, in a sense, a fundamental part of what we communicate by speech. And if you think about your own reactions to people, you'll understand that that's true. As I mentioned, every prolonged dialog between people involves a play of facial expressions, as well as the words that are conveyed. And that's why it's often much more effective to talk with someone about something that's difficult face-to-face, than by email, for example. Okay. Faces convey much information about an individual in addition to that about mood and feelings. Faces provide visual information about gender. Okay. Age. Admittedly, I've chosen those examples to maximize the contrast. There may also be a size difference between these two people. But even just from the photographs, you know, that you're looking at a baby, here, a very young person. And an older person, there. Ethnicity, as an example. And character. Now, this is the most tricky and perhaps the most ambiguous. So, to weight the scales, I've contrasted Abraham Lincoln with Rasputin. But. And there are some wonderful pictures of Rasputin, in which his eyes look positively crazy. But I think even if you didn't know anything about the history. The historical importance of these people, these two individuals and what they were like. I think that if you saw lots of pictures of Lincoln and of this man, you would conclude that this man was, indeed, more trustable. It really comes through in his facial expressions and the set of his face. Okay. So, the face provides a tremendous amount of information to our fellows, often just at a glance. And these are an important part of our social interactions. So, faces provide an instant visual identification of a particular individual. In effect, of the 7.3 billion people on earth today, there are about that many distinguishable faces. Of course, identical twins and triplets are an exception. But, indeed, most human faces are at least slightly different from other faces, and often very different. So, and rapid visual identification is an invaluable aid in social interactions. And this is just an obvious point, when you walk into a room, you look for people you know. You do it almost immediately, from their face. Yes, there may be hints about from their size or body build, and so on. But the face is the main provider of information about who you're looking for. So, is there an evolutionary explanation for facial differences? Yes. If facial differences provide quick individual identification, and if that identification promotes social interactions, most of which are positive, helpful. Then, it will be selection for such differences. Now, there is actually beginning to be a genetics of facial difference. I'm going to just go over this very lightly, because I think it gets into too much detail for the time I have allowed. I'm not even sure if I've exceeded that time. So, I'm just going to leave this with you as a specific point. That it's now possible to identify specific genetic differences as correlating with individual specific facial differences. There is beginning to be a true genetics of facial difference. There are at least, at this point, 20 genes that are identified with specific facial differences. And at some point, just from sequenced genomes, alone. And the genes that are involved in creating facial differences, one may be able to actually reconstruct what the faces looked like form their genetic differences. This is really, it's still for the future, but it's within the realm of possibility, now. So, with those findings, can facial differences be related to social selection? Namely, selection for individuals within a particular social context. Almost certainly. A new work shows that quantitatively, faces are indeed more morphologically diverse than other regions of the body. Okay. So, our faces show more differences than any other part of our body. The genes implicated in generating facial differences are under selection to be different. The phenomena of negative frequency dependent selection, or NFDS. This is an awkward term and we can forget it. But the important point is that it seems that there actually is selection for us to have different faces, so that we can recognize each other very quickly. And this only makes sense in terms of facial difference actually promoting interactions that are ultimately helpful. This point could be elaborated a lot, and it's interesting. But there isn't time. So, I'm now coming to the close of the lecture and just summing up. So, what was the major net effect of the changes that led from fish faces to the human face? So, let's first just look at fish faces. And it's not just fish faces, but the faces shown by fish, amphibia, reptiles, and birds. The four major classes apart from the mammals, amongst the vertebrates. The animals with backbones. So, these faces were, indeed, the sensory headquarters of the animal. And the site of food ingestion in the mouth. Primarily, the face existed as a receiver of information about the world. And initially, for the animal to find food. Now, with the mammals, there began to be real facial expressions, and hence, information to other members of the same species about what was going on in the mind of the animal making these expressions. So, there were the same functions as found in the other kinds of vertebrates. Plus, the face is the provider of some information to others. And with us, in the genus homo, and specifically our own species, homo sapiens. There were all the same original functions of the face. Okay. For locating food and so on. Plus, it was a provider. The face has become a provider of huge amounts of information about the individual. And this is of social value. The face is a storehouse and transmitter of information. Okay. So, the earliest vertebrate face is where primarily receivers. Sorry, were primarily receivers of information about the world. And of course, as a site of ingestion for food. Our face is certainly a storehouse of information about the face. But it also conveys that information to the fellow members of our species. It's a fairly fundamental difference. And of course, as I've stressed, this is shared with our nearest relatives. But also, to some extent, with more distant mammalian relatives. But we've taken it to an extreme. So, summing up, I'll just read this out. ''For about 450 million years of evolutionary history, the faces of vertebrates functioned primarily as the sensory headquarters of the individual''. Okay. The concentrated areas in which three of the main senses are localized. Initially, and particularly the search for and ingestion of food. Furthermore, a point that I haven't really elaborated, but I'll state it, here. ''Matters of diet influenced the shape of jaws and teeth and the placement of the sensory apparatus. And therefore, the shape and structure of the face''. Okay. So, matters of diet were really crucial in shaping the evolution of the face for most of vertebrate history. ''For 50 or so million years, in the anthropoid primates'', specifically, ''the social environment played an increasing role. Becoming even stronger and more complex in the hominins''. The hominins being our group. ^M00:50:00 ''Thus, social selection played a major part in shaping the human face in all its unusualness. We are the most sociable of animals. And the physical characteristics of the human face reflect a long history of increasingly complex social interactions''. And that in a sense, is the main message from this talk. But I'd like to end with an additional thought. And even a bit of advice. And that is that the capacity of our face to give out information is incredibly valuable and unusual. And more than 50 million years of anthropoid primate evolution have been invested, in a sense. Not by anybody deliberately making it so, it just happened. Have been 50 million years of primate evolution have been invested to make our faces superb instruments for communicating our thoughts and feelings. I urge you to take advantage of that, as much as possible. If you want to communicate something important and/or complex to someone, do it face-to-face, not by email. At least by Skype. Okay. And I think with that, I'll close. So, thank you, very much, for your attention. ^M00:51:11 [ Applause ] ^M00:51:13 >> Mr. Wilkins. >> Adam Wilkins: Yes. >> Can you explain exactly how the genetic selection [inaudible]difference from other people [inaudible] or facial characteristics [inaudible]? >> Adam Wilkins: Yeah. So, I think you're asking me what is negative frequency dependent selection. This is the awkward term. How can there be selection for difference? And it depends on. I think in this case, certainly, it depends on people perceiving difference and finding it attractive. So, we all know. So, it comes into probably what's termed sexual selection, where there is a special set of things that influence the selection of characteristics that have to do with mating. Whom you want to link up with. And so, it's almost certainly something that has been. And I think it's almost certain, this preference for slight difference is connected with what we find attractive in others. This point hasn't yet, has not received a lot of attention. The main findings that really support this idea, came out only a year or two, ago, from a guy named Michael Shin, who. Yeah, Shin, who is a professor at Cornell University. So, I think that's all I can say about it. But basically, it comes down to the fact that people like a degree of difference, when selecting their mates. And this has the side effect of helping to make us all different. Which has the important additional value that in social interactions we can identify each other, much more readily. Without this negative frequency dependent selection, we might be tending to be more homogenous. There would be less facial difference and more similarity, time. But here we are, standing at 7.3 billion people on earth with nearly that many different and discernably different faces. And it must have something to do with the fact that difference in our perspective mates, slight facial differences often are attractive. I'm not sure I can say anything more about it, than that. But that's the rough idea. Yes. Oh, sorry. >> There was a lot [inaudible]. Public channel, or something like that, about what makes, I guess humans attracted to one another. But not just humans. But right now, my question is about this thing that they said about facial symmetry. >> Adam Wilkins: Mm-hmm. >> They were really talking about people who are looking for mates who are the healthiest and the most likely to propagate the species. >> Adam Wilkins: Yes. >> But that so what they were looking for was [inaudible]. Facial symmetry and a chart that showed that some actor had like their perfect face. >> Adam Wilkins: Yes. >> That they [inaudible]. But that instead of looking for differences, they were actually looking for like a [inaudible] was the perfect healthiest. >> Adam Wilkins: So, this idea is what I believe, and there's a lot of supporting evidence for it. That a symmetrical face is really, highly symmetrical faces are more attractive to members of the opposite sex, than more visibly asymmetric faces. So, there is a fair amount of scientific data supporting this. I'm not sure I'm equipped to say anything more than that. But that comes into it. Does that help answer your question? Or? >> Well, I just sort of [inaudible] that [inaudible]. >> Adam Wilkins: It's a slightly different. Yeah. >> Selections. >> Adam Wilkins: Yeah. Yeah. Yeah. I think the idea, in general, is that more symmetric faces indicate kind of a better construction of the person as a whole. And I think we all know that we find more symmetrical faces inherently more attractive than more visibly asymmetric ones. And that must affect the likelihood with which one can mate with others. ^M00:56:09 ^M00:56:13 Yes. >> Did I hear you say? Did I correctly hear you say that thought processes helped to shape the brain? And if so, how did they do that? >> Adam Wilkins: Well, I'm not sure I said exactly that. But thought processes certainly affect our behavior. And our behaviors then, our, in the sense of animals. And an animal's behavior will affect how well it survives. And hence, you know, whether it's likely to have more progeny or not. Does that help out? >> [inaudible] actually affect the physical structure? >> Adam Wilkins: So, it's indirect, okay. So, there's a selection for neural superstructure that permits or promotes certain kinds of behaviors. Which in turn, are either more favorable or less for promoting the survival of the animal. So, it's an indirect way of affecting the likelihood of selection for an animal with those properties. Yes. >> I understand that humans evolved in small groups of maybe 100 or so. >> Adam Wilkins: Yes. >> Individuals. >> Adam Wilkins: Yes. >> And so, it seems to me, listening to your discussion, that we only need to distinguish about 100 different facial arrangements, something like that. According to the evolutionary analysis. And so, in the modern world where you're living in cities of millions, you have to have social evolution to contribute to the distinctiveness of all the individuals. And my thinking, as you're talking, is that you've also explained the evolution of all kinds of social phenomena, like [inaudible] for instance. I don't know what [inaudible]. >> Adam Wilkins: Yes. So, we are used to a world of cities and towns and large numbers of people. Most of the evolution I've discussed occurred when the groups of humans were much smaller. But there's undoubtedly, evolutionary selection going on, today, in these very large mixed groups. I mean, what we have, today, is really unprecedented in the evolution of our species, or indeed, any species. This going from small interactive groups to potentially huge ones. So, does that pertain to what you're saying? I'm. >> I wasn't thinking of that, but that's okay. Because I can see that [inaudible]. >> Tomoko Steen: You can [inaudible]. >> Adam Wilkins: Yeah. But. >> Judging from your facial features. ^M00:59:06 [ Laughter ] ^M00:59:08 >> Yes. >> Tomoko Steen: Please join me to thank today's speaker, again. Thank you, very much. ^M00:59:14 [ Applause ] ^M00:59:16 >> This has been a presentation of the Library of Congress. Visit us at loc.gov.