A world renown paleoanthropologist cuts down old notions of our family tree to reveal a host of unknown ancestors: extinct human species
Like most people, I was taught to think of human evolution as a linear chain, with a "missing link" connecting apes and a series of prototype humans in a process of perfection reaching the pinnacle that we occupy today. This is the traditional view of paleoanthropologists, veritable human fossil hunters who try to piece together our history. But the field is now increasingly divided and you are seen as the leader of a new and growing camp. Please explain.
This notion of human evolution as being a linear trudge from primitivism to perfection is totally wrong. I came to paleoanthropology from the study of lemurs [monkey-like primates] in Madagascar where you have a huge diversity of animals. You cannot help asking, "How did these creatures become so diverse?" Yet this question is not asked in paleoanthropology because there is only one species of humans today. Somehow we believe it is normal and natural for us to be alone in the world. Yet in fact, if you look at the fossil record, you find that this is totally unusual--this may be the first time that we have ever had just one species of humans in the world.
We have a history of diversity and competition among human species which began some five million years ago and came to an end with the emergence of modern humans. Two million years ago, for example, there were at least four human species on the same landscape. Maybe they got along by basically ignoring each other or even having peaceful interactions. We don't know.
In any event, we are now the sole surviving twig on a big branching bush produced by this process of evolutionary experimentation. We're not the pinnacle of a ladder that our ancestors laboriously climbed.
How do your views on human evolution differ from traditional Darwinian notions?
According to Darwin, you have legions of organisms that over time evolve themselves into a new species. It's like a fine-tuning process, guided by natural selection, in which the individuals best-adapted to their environment reproduce and pass on their "favourable" characteristics, so that each generation improves upon its predecessor.
So we tend to think of evolution in terms of characteristics, rather than species. For example, we speak of the "evolution of upright walking" or the "evolution of the hand," often without realizing that legs and hands can only be part of the story. The reality is that natural selection is a blind mechanism which can vote up or down only on entire organisms, warts and all. Individual organisms are mindboggingly complex and integrated mechanisms: they succeed or fail as the sum of their parts, not because of a particular characteristic.
It's the same with populations and species. Species are out there competing with others in a real world of limited resources. What's more, the ecologies of which they form a part have an alarming tendency to change abruptly. If your habitat is covered by an ice sheet, it's pretty irrelevant how well you are adapted to the meadows and forests now buried beneath the ice.
Finally in the Darwinian notion you have a slow accumulation of changes over generations leading to the creation of a new species [when individuals of the same lineage can no longer reproduce]. However a population will change morphologically [biologically] with time but this anything. You're doing your best to reconstruct evolutionary history and you know that science in general is a system of provisional knowledge--it's not an authoritarian system of belief where you make "a" discovery and that stays definitive for the rest of time. All that scientists know is that what we believe today is probably not going to be what we believe tomorrow. Science is grounded in doubt.
But some people are more willing to accept this provisional nature than others. You probably have colleagues fuming with your ongoing list of human species.
It's just because they're not used to it. It's hard to convince people to reconsider fossils they thought they have known for over 30 years. But they are more flexible with new fossils because they don't have any received wisdom about species no one knew existed before.
This seems to be the heyday of geneticists. There is a strong feeling that if they can just manage to extract the DNA from human fossils, we will finally get to the bottom of our evolutionary history. Do you think genetic research will transform the field of paleoanthropology?
My feeling is that the two sets of data are still pointing in the same general direction of multiple human species. And that is comforting. But there are paleoanthropologists out there feeling depressed and saying, "Oh God! Our data don't have the resolution that molecules have and we should always believe molecules above morphology." But I don't think that is true. There are no magic bullets. We can widen the field with genetic and isotope studies but we will learn the most by persuading people to look more closely at the existing fossils.
A battle is raging between sociobiologists and cultural anthropologists. Basically, sociobiologists believe that humans all share some kind of essential nature shaped by evolution. Cultural anthropologists, in contrast, vehemently reject universal statements about human nature and focus on local context in explaining our behaviour. Where do you stand?
I'm not certain about what the cultural anthropologists stand for. But the general feeling is that history is driven in some way by cultural factors. Yet I see a lot of randomness and contingency in history.
On the other hand, these evolutionary psychologists [sociobiology applied to our species] are completely misled. For example, say they want to explain something like violence. They will treat it as a separate category and then develop just so stories as to why that particular characteristic emerged in evolution, all the while forgetting that any characteristic is embedded in a very complex organism.
You've raised the issue of violence. Why do you think we have a tendency towards aggression? Why can't one generation learn from the next and avoid conflict?
We are psychologically so complex--or perhaps screwed up--at least partly because of the way in which our brains were built up over the ages, structure on structure. While the old notion of an inherent conflict between older and newer brain structures and functions seems oversimplified, it is self-evident that it is in our controlling organ, the brain, that we must search for the keys to the contradictions that we all exhibit, every day.
Hold on. I thought you just rejected the evolutionary biologists' penchant for looking to biology to explain our behaviour.
In my book Becoming Human, I write that it may seem odd to devote hundreds and hundreds of pages to ways of looking at the fossil record and then conclude that you cannot learn much from it about how people behave today. If you really want to understand what humans are, don't look to the past, look to how people are in the present.
Not only do we look to the past to understand the present but we project the present on interpretations of the past. For example, the Neanderthals are veritable icons, yet they were just one actor on a huge stage. How do you explain this emotional attachment?
Neanderthals were very happy living in Europe for 200,000 years and suddenly modern Homo sapiens show up and BOOM! They're gone. So to make it more palatable, some people have been suggesting, "Well, maybe they were just genetically swamped by hordes of invading modern humans." I don't think that can possibly have been the case. Neanderthals and modern Homo sapiens are just too different to have interbred successfully. But if it makes people feel better about poor old Neanderthal being genetically swamped than physically annihilated, then so be it.
One thing truly sets us apart from every other species: consciousness. Human consciousness has been described as a kind of inner eye, which allows the brain to observe itself at work and therefore permits us to have the complex interpersonal relationships that far exceed those of any other animal. Modern human anatomy goes back over 100,000 years but it wasn't until maybe 40,000 years ago that modem cognition suddenly burst on the scene, as evidenced by the cave art of the CroMagnon, for example, in Europe. What triggered this cognitive explosion?
It is impossible to be sure what this innovation might have been, but the best current bet is that it was the invention of language. For language is not simply the medium by which we express our ideas and experiences to each other. Rather it is fundamental to the thought process itself. It involves categorizing and naming objects and sensations in the outer and inner worlds and making associations between resulting mental symbols. It is impossible for us to conceive of thought (as we know it) in the absence of language, and it is the ability to form mental symbols that is the fount of our creativity, for only once we create such symbols can we recombine them and ask questions like "What if...?"
Why haven't other species developed spoken language?
Many species have very complex vocal, gestural and scent-based systems of communication but even in the great apes, vocalizations seem limited to expressing emotional states. We have managed to separate vocal sounds from emotion, and instead to attach them to symbols that we form in our minds. As far as we know, this is a unique ability that was only relatively recently acquired. In fact, if we were to set the evolutionary clock back only a few hundred thousand years and run the whole process all over again, it's not clear to me that we could necessarily expect to see a linguistic Homo sapiens emerge again. There is just so much randomness in nature.
Do you remember the first time you entered the cave of Lascaux in France? The art inside dates back about 30,000 years ago.
I've never had a more profound or powerful experience. It is such extraordinary art in such an extraordinary environment--the age is only a secondary part of that experience. This symbolic activity appeared so suddenly: art and carving, engraving, notation music, people decorating their bodies and burying each other in elaborate styles and so on.
You've maintained that this kind of symbolic activity was for the most part reserved to Europe. Perhaps it was occurring elsewhere in Africa or Asia but just slipped through the cracks of a sparse fossil record? You could be accused of Eurocentrism.
We have some early hints in Africa of humans transporting exotic materials over long distances, some traces of flint mining and 50,000-year-old ostrich eggshell beads and so on. People may have even been navigating to Australia 60,000 years ago. These are all things that probably required the same kind of cognitive apparatus that produced Lascaux. But the record is tantalizingly poor.
This isn't to suggest that any of this cognition and creativity originated in Europe. Apparently the first CroMagnon brought these capacities with them but from where we don't know. It may well have begun in Africa. But right now, the best record that we have is in Europe. And that's why it attracts so much attention. Hopefully, we'll be learning more from other parts of the world as we make more discoveries.
You've suggested that the art at Lascaux reflected a body of methology, a view of the world and humanity's place in it. Do you think this thirst or quest to understand our origins is a distinctly human trait?
Oh yes. This intense curiosity about our origins, this intense need to know "why" is a profound part of us. I think the bottom line is that the ability and desire to ask these questions are deeply embedded in the human psyche. We are trying to satisfy this curiosity when we study human evolution. Indeed we may not be learning nearly as much about ourselves as we think we are.
For many people, the ultimate question is whether primitive man was more noble or "better off" than civilized man. In your opinion, did a state of grace, so to speak, exist before or after the advent of civilization as we know it?
(Burst of laughter) First, a state of grace is a concept which humans devise while knowing that it doesn't exist. Most of us are in states of disgrace and always shall be.
Second, ethics are all products of the human mind. We cannot derive any concepts of morality or of natural law from contemplating nature. The reason why is that nature is indifferent to individual suffering or success and to call such indifference amoral would be to anthromorphize.
Human evolution has come to a standstill, you say. We haven't really changed since acquiring cognition and we cannot expect any major innovations in the future. What is holding us back?
You've got to have small populations in order to get meaningful genetic innovations. The population is getting larger all the time, individuals are infinitely more mobile now and the prospect of isolation of populations is lower than it ever has been. We can imagine some sci-fi scenarios of isolated space colonies but they would inevitably be sustained by a lifeline from Earth. Or we can imagine genetic engineering. However, artificially produced genotypes could only be sustained by sequestering "engineered" individuals which I doubt and hope would never be deemed permissible. But if it was, these genetic innovations would remain only among these small "laboratory" populations.
So to hope that a bit more evolutionary fine-tuning will solve our problems is foolish optimism. We have to cope with ourselves as we currently cope with the world and the problems that we cause in it. We have reached a pinnacle in the sense that Homo sapiens is truly something unique. Whether you think it is superior or not is up to you. I suspect that if other species were capable of contemplating this question, they would not conclude that we represent a pinnacle.
In the world's richest, most industrialized country, the United States, a debate rages over the teaching of human evolution in highschools. The "creationist" movement wants to impose Biblical scriptures in the classroom. Has this movement hampered your work? The Internet has a long list of sites in which creationists not only attack your work but also pray for your soul.
It's absolutely appalling. This is the only country where this is happening. It's due to a certain group of fundamentalist Protestants who seem to feel that human beings need the word of God in order to behave properly. They're threatened, insecure and looking for a scapegoat.
I get an occasional letter from creationists who are very concerned about my soul and insist that I follow the "true path." But I've never received any threats or felt any restrictions in my work.
For a man who studies dead people, you seem to go out on a limb politically. You cannot avoid the ire of the creationists but you have gone a step further by writing that attempts to limit women's reproductive rights are "the ultimate example of human hubris" at a time when global human population growth is causing ecological havoc. Why go so far?
I just draw conclusions on the basis of what I see around me in the world as a human being, not as a paleoanthropologist. I'm concerned about this emphasis on the quantity of life because it's ultimately going to have a deleterious effect on its quality. There are three times as many people in the world as there were when I was born. But it cannot go on indefinitely...
Specimen: Ian Tattersall
Species: Homo sapiens
Origin: Born in England, raised in East Africa
Status: Curator of Anthropology at the American Museum of Natural History, New York City Personal evolution: Followed in the footsteps of his illustrious predecessorCharles Darwin by studying at Cambridge University's Christ's College of where he majored in anthropology and archaeology. However, he strayed from the path of human evolution as a PhD student by leaping to the study of primates, notably lemurs (small mon keylike creatures) in Madagascar as well as monkeys in Mauritius.
Distinguishing features: Two unusual traits resulted from time spent in the jungle with our primate cousins: first, a critical eye to recognize the diversity of our human ancestors; second, a deep respect for nature which has led to the conclusion that his own species is a monster, whose ravenous appetite and irrational behaviour imperils the world.
Historical significance: Leader of the camp to knock our species off the pedestal of human evolution.