"Race" is not a clearly defined word. "Species" is different. There really is an agreed way to decide whether two animals belong in the same species: can they interbreed? The interbreeding criterion gives the species a unique status in the hierarchy of taxonomic levels. Above the species level, a genus is just a group of species whose members are pretty similar to each other. No objective criterion exists to determine how similar they have to be, and the same is true of all the higher levels: family, order, class, phylum and the various "sub-" or "super-" names that intervene between them. Below the species level, "race" and "sub-species" are used interchangeably and, again, no objective criterion exists that would enable us to decide whether two people should be considered part of the same race or not, nor to decide how many races there are. And of course there is the added complication, absent above the species level, that races interbreed, so there are lots of people of mixed race.
The interbreeding criterion works pretty well, and it delivers an unequivocal verdict on humans and their supposed races. All living human races interbreed with one another. We are all members of the same species, and no reputable biologist would say any different. But let me call your attention to an interesting, perhaps even slightly disturbing, fact. While we happily interbreed with each other, producing a continuous spectrum of inter-races, we are reluctant to give up our divisive racial language. Wouldn't you expect that if all intermediates are on constant display, the urge to classify people as one or the other of two extremes would wither away, smothered by the absurdity of the attempt, which is continually manifested everywhere we look? But this is not what happens, and perhaps that very fact is revealing.
People who are universally agreed by all Americans to be "black" may draw less than one eighth of their ancestry from Africa, and often have a light skin colour well within the normal range for people universally agreed to be "white." In the picture on the next page of four American politicians, two are described in all newspapers as black, the other two as white. Wouldn't a Martian, unschooled in our conventions but able to see skin shades, be more likely to split them three against one? But in our culture, almost everybody will immediately "see" Colin Powell as "black," even in this particular photograph which happens to show him with possibly lighter skin than both George W Bush and Donald Rumsfeld.
Now look at Powell standing next to a genuinely black man, Daniel arap Moi, former president of Kenya. The text accompanying the photograph, in the web magazine Salon from May 2001, made much of Powell's "near-Messianic treatment in Africa… because he is black." Why do people so readily swallow the apparent contradiction - and there are many similar examples - between the verbal statement, "he is black," and the picture it accompanies?
What is going on here? Various things. First, we are curiously eager to embrace racial classification, even when talking about individuals whose mixed parentage seems to make a nonsense of it, and even where it is irrelevant to anything that matters. Second, we tend not to describe people as of mixed race. Instead, we plump for one race or the other. Some American citizens are of pure African descent and some are of pure European descent (leaving aside the fact that, in the longer term, we are all of African descent). Maybe it is convenient for some purposes to call these people black and white respectively, and I am not proposing any principled objection to these names. But many people - probably more than most of us realise - have both black and white ancestors. If we are going to use colour terminology, many of us are presumably somewhere in between. Yet society insists on calling us one or the other. It is an example of what, in the "Salamander's Tale" chapter of my new book, I have called the "tyranny of the discontinuous mind." Americans are regularly asked to fill in forms in which they have to tick one of five boxes: Caucasian (whatever that means - it certainly doesn't mean from the Caucasus), African-American, Hispanic (whatever that means - it certainly does not mean, as the word seems to suggest, Spanish), Native American or Other. There are no boxes labelled "half and half." But the very idea of ticking boxes in this way is incompatible with the truth, which is that many, if not most, people are a complex mix of the offered categories and others. My inclination is irritably to refuse to tick any boxes, or to add my own box labelled "human."
Third, in the particular case of "African-Americans," there is something culturally equivalent to genetic dominance in our use of language. When Mendel crossed wrinkled peas with smooth peas, all the first generation progeny were smooth. Smooth is "dominant," wrinkled is "recessive." The first generation progeny all had one smooth allele and one wrinkled, yet the peas themselves were indistinguishable from peas with no wrinkled genes. When a white man marries a black woman, the progeny are intermediate in colour and in most other characteristics. This is unlike the situation with peas. But we all know what society will call such children: "black." Blackness is not a true genetic dominant like smoothness in peas. But social perception of blackness behaves like a dominant. It is a cultural or memetic dominant. The anthropologist Lionel Tiger attributes this to a racist "contamination metaphor" within white culture. And no doubt there is also a strong and understandable desire on the part of the descendants of slaves to identify with their African roots.
Fourth, there is high interobserver agreement in our racial categorisations. A man such as Colin Powell, of mixed race and intermediate physical characteristics, is not described as white by some observers and black by others. A small minority will describe him as mixed. All others will without fail describe Powell as black - and the same goes for anybody who shows the slightest trace of African ancestry, even if their percentage of European ancestors is overwhelming. Nobody describes Colin Powell as white.
There is a useful technique in science called "interobserver correlation." It is a measure that is often used to establish that there really is a reliable basis for a judgement, even if nobody can pin down what that basis is. The rationale, in the present case, is this. We may not know how people decide whether somebody is "black" or "white," but there must be some sort of reliable criterion lurking there because any two randomly chosen judges will come to the same decision. The fact that the interobserver correlation remains high, even over a huge spectrum of inter-races, is testimony to something deep-seated in human psychology. (It is reminiscent of the anthropologists' finding about perception of hue. Physicists tell us that the rainbow is a simple continuum of wavelength. It is biology and/or psychology, not physics, that singles out particular landmark wavelengths along the physical spectrum for naming. Blue has a name. Green has a name. Blue-green does not. The interesting finding of anthropologists' experiments is that there is substantial agreement over such namings across different cultures. We seem to have the same kind of agreement over judgements of race. It may prove to be even stronger and clearer than for the rainbow.)
Whatever we may think as observers of superficial appearances, the human species today is, to a geneticist, especially uniform. Taking such genetic variation as the human population does possess, we can measure the fraction that is associated with the regional groupings that we call races. And it turns out to be a small percentage of the total: between 6 and 15 per cent, depending on how you measure it - much smaller than in many other species where races have been distinguished. Geneticists conclude, therefore, that race is not a very important aspect of a person. There are other ways to say this. If all humans were wiped out except for one local race, the great majority of the genetic variation in the human species would be preserved. This is not obvious and may be surprising to some people. If racial statements were as informative as most Victorians used to think, for example, you would need to preserve a spread of all the different races in order to preserve most of the variation in the human species. Yet this is not the case.
It certainly would have surprised Victorian biologists who, with few exceptions, saw humanity through race-tinted spectacles. Their attitudes persisted into the 20th century. Hitler was unusual in gaining the power to turn racialist ideas into state policy. Many others had similar thoughts but lacked the power. HG Wells's vision of his New Republic (Anticipations, 1901) is a salutary reminder of how a leading British intellectual, regarded in his time as progressive, could say horrifying things only a century ago and scarcely be noticed doing so: "And how will the New Republic treat the inferior races? How will it deal with the black?… the yellow man?… the Jew?… those swarms of black, and brown, and dirty-white, and yellow people, who do not come into the new needs of efficiency? Well, the world is a world, and not a charitable institution, and I take it they will have to go… And the ethical system of these men of the New Republic, the ethical system which will dominate the world state, will be shaped primarily to favour the procreation of what is fine and efficient and beautiful in humanity - beautiful and strong bodies, clear and powerful minds… And the method that nature has followed hitherto in the shaping of the world, whereby weakness was prevented from propagating weakness… is death… The men of the New Republic… will have an ideal that will make the killing worth the while."
I suppose we should take comfort from the change that has come over our attitudes during the intervening century. Perhaps, in a negative sense, Hitler can take some credit for this, since nobody wants to be caught saying anything that he said. But what, I wonder, will our successors of the 22nd century be quoting, in horror, from us? Something to do with our treatment of other species, perhaps?
But that was an aside. We were dealing with the unusually high level of genetic uniformity in the human species, despite superficial appearances. If you take blood and compare protein molecules, or if you sequence genes themselves, you will find that there is less difference between any two humans living anywhere in the world than there is between two African chimpanzees. We can explain this human uniformity by guessing that our ancestors, but not those of the chimpanzees, passed through a genetic bottleneck, perhaps within the last 100,000 years. The population was reduced to a small number, came close to going extinct, but pulled through. Like the children of Noah in the myth, we are all descended from this small population, and that is why we are so genetically uniform.
Some people find the evidence of biochemical genetics unsatisfying because it seems not to square with their everyday experience. We don't "look" uniform. Norwegians, Japanese and Zulus really do look rather dramatically different from one another. With the best will in the world, it is intuitively hard to believe what is in fact the truth: that they are "really" more alike than three chimpanzees who look, to our eyes, much more similar. This is, of course, a politically sensitive matter, a point I heard being amusingly lampooned by a west African medical researcher at a gathering of about 20 scientists. At the beginning of the conference, the chairman asked each of us around the table to introduce ourselves. The African, who was the only black person there, happened to be wearing a red tie. He finished his self-introduction by saying, "You can easily remember me. I am the one with the red tie." He was genially mocking the way people bend over backwards to pretend not to notice racial differences. Nevertheless, we can't write off the genetic evidence which suggests that, all appearances to the contrary, we really are an unusually uniform species. What is the resolution to the apparent conflict between appearance and measured reality?
It is genuinely true that, if you measure the total variation in the human species and then partition it into a between-race component and a within-race component, the between-race component is a very small fraction of the total. Only a small admixture of extra variation distinguishes races from each other. That is all correct. What is not correct is the inference that race is therefore a meaningless concept. This point has been clearly made by the distinguished Cambridge geneticist AWF Edwards in a recent paper called "Human genetic diversity: Lewontin's fallacy." RC Lewontin is an equally distinguished Cambridge (Mass) geneticist, known for the strength of his political convictions and his weakness for dragging them into science at every opportunity. Lewontin's view of race has become near-universal orthodoxy in scientific circles. He wrote, in a famous paper of 1972: "It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals."
This is exactly the point I accepted above, not surprisingly, since what I wrote was largely based on Lewontin. But see how Lewontin goes on: "Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance."
We can all happily agree that human racial classification is of no social value and is positively destructive of social and human relations. That is one reason why I object to ticking boxes in forms and why I object to positive discrimination in job selection. But that doesn't mean that race is of "virtually no genetic or taxonomic significance." This is Edwards's point, and he reasons as follows. However small the racial partition of the total variation may be, if such racial characteristics as there are are highly correlated with other racial characteristics, they are by definition informative, and therefore of taxonomic significance.
"Informative" means something quite precise. An informative statement is one that tells you something you didn't know before. The information content of a statement is measured as reduction in prior uncertainty. If I tell you that Evelyn is male, you immediately know a whole lot of things about him. Your prior uncertainty about the shape of his genitals is reduced. You now know facts you didn't know before about his chromosomes, his hormones and other aspects of his biochemistry, and there is a quantitative reduction in your prior uncertainty about the depth of his voice, and the distribution of his facial hair and of his body fat and musculature. Contrary to Victorian prejudices, your prior uncertainty about Evelyn's general intelligence, or ability to learn, remains unchanged by the news about his sex. Your prior uncertainty about his ability to lift weights or excel at most sports is quantitatively reduced, but only quantitatively. Plenty of females can beat plenty of males at any sport, although the best males can normally beat the best females. Your ability to bet on Evelyn's running speed, say, or the power of his tennis serve, has been slightly raised by my telling you his sex, but it has not reached certainty.
Now to the question of race. If I tell you Suzy is Chinese, how much is your prior uncertainty reduced? You now are pretty certain that her hair is straight and black (or was black), that her eyes have an epicanthic fold, and one or two other things about her. If I tell you Colin is "black," this does not, as we have seen, tell you he is black. Nevertheless, it is not uninformative. The high interobserver correlation suggests that there is a constellation of characteristics that most people recognise, such that the statement "Colin is black" really does reduce prior uncertainty about Colin. It works the other way around to some extent. If I tell you Carl is an Olympic sprinting champion, your prior uncertainty about his "race" is, as a matter of statistical fact, reduced. Indeed, you can have a fairly confident bet that he is "black."
We got into this discussion through wondering whether the concept of race was, or had ever been, an information-rich way to classify people. How might we apply the criterion of interobserver correlation to judging the question? Well, suppose we took full-face photographs of 20 randomly chosen natives of each of the following countries: Japan, Uganda, Iceland, Sri Lanka, Papua New Guinea and Egypt. If we presented 120 people with all 120 photographs, my guess is that every single one of them would achieve 100 per cent success in sorting them into six different categories. What is more, if we told them the names of the six countries involved, all 120 subjects, if they were reasonably well educated, would correctly assign all 120 photographs to the correct countries. I haven't done the experiment, but I am confident that you will agree with me on what the result would be. It may seem unscientific of me not to bother to do the experiment. But my confidence that you, being human, will agree without doing the experiment is the very point I am trying to make. If the experiment were to be done, I do not think Lewontin would expect any other result than the one I have predicted. Yet an opposite prediction would seem to follow from his statement that racial classification has virtually no taxonomic or genetic significance.
In short, I think Edwards is right and Lewontin wrong. Nevertheless, I strongly support Lewontin's statement that racial classification can be actively destructive of social and human relations - especially when people use racial classification as a way of treating people differently, whether through negative or positive discrimination. To tie a racial label to somebody is informative in the sense that it tells you more than one thing about them. It might reduce your uncertainty about the colour of their hair, the colour of their skin, the straightness of their hair, the shape of their eye, the shape of their nose and how tall they are. But there is no reason to suppose that it tells you anything about how well qualified they are for a job. And even in the unlikely event that it did reduce your uncertainty about their likely suitability for some particular job, it would still be wicked to use racial labels as a basis for discrimination when hiring somebody. Choose on the basis of ability, and if, having done so, you end up with an all-black sprinting team, so be it. You have not practised racial discrimination in arriving at this conclusion.
A great conductor, when auditioning instrumentalists for his orchestra, always had them perform behind a screen. They were told not to speak, and they even had to remove their shoes for fear the sound of high heels would betray the sex of the performer. Even if it were statistically the case that women tend to make better harpists, say, than men, this does not mean that you should actively discriminate against men when you choose a harpist. Discriminating against individuals purely on the basis of a group to which they belong is, I am inclined to think, always wrong. There is near-universal agreement today that the apartheid laws of South Africa were evil. Positive discrimination in favour of "minority" students on American campuses can fairly be attacked on the same grounds as apartheid. Both treat people as representative of groups rather than as individuals in their own right. Positive discrimination is sometimes advocated as redressing centuries of injustice. But how can it be just to pay back a single individual today for the wrongs done by long dead members of a plural group to which he belongs? People are individuals; they are individually different, far more different from other members of their group than their groups are from each other. In this, Lewontin is clearly right.
Interobserver agreement suggests that racial classification is not totally uninformative, but what does it inform about? About things like eye shape and hair curliness. For some reason it seems to be the superficial, external, trivial characteristics that are correlated with race - perhaps especially facial characteristics. But why are human races so different in just these superficially conspicuous characteristics? Or is it just that we, as observers, are predisposed to notice them? Why do other species look comparatively uniform whereas humans show differences that, were we to encounter them elsewhere in the animal kingdom, might make us suspect we were dealing with a number of separate species?
The most politically acceptable explanation is that the members of any species have a heightened sensitivity to differences among their own kind. On this view, it is just that we notice human differences more readily than differences within other species. Chimpanzees whom we find almost identical look just as different, in chimpanzee eyes, as a Kikuyu looks different to a Dutchman in our eyes. Expecting to confirm this kind of theory at the within-race level, the American psychologist HL Teuber, an expert on the brain mechanisms of facial recognition, asked a Chinese student to study the question, "Why do westerners think Chinese people look more alike than westerners?" After three years of intensive research, the Chinese student reported his conclusion: "Chinese people really do look more alike than westerners!" Teuber told the story with much wiggling of eyebrows, a sure sign with him that a joke was on the way, so I don't know what the truth of the matter is. But I have no difficulty in believing it, and I certainly don't think it should upset anyone.
Our recent worldwide diaspora out of Africa has taken us to an extraordinarily wide variety of habitats, climates and ways of life. It is plausible that the different conditions have exerted strong selection pressures, particularly on externally visible parts, such as the skin, which bear the brunt of the sun and the cold. It is hard to think of any other species that thrives so well from the tropics to the Arctic, from sea level to the high Andes, from parched deserts to dripping jungles. Such different conditions would be bound to exert different natural selection pressures, and it would be surprising if local populations did not diverge as a result. Hunters in the deep forests of Africa, South America and southeast Asia have all become small, almost certainly because height is a handicap in dense vegetation. Peoples of high latitude, who, it has been surmised, need all the sun they can get to make vitamin D, tend to have lighter skins than those who face the opposite problem - the carcinogenic rays of the tropical sun. It is plausible that such regional selection would especially affect superficial characteristics like skin colour, while leaving most of the genome intact and uniform.
In theory, that could be the full explanation for our superficial and visible variety, covering deep similarity. But it doesn't seem enough to me. At the very least, I think it might be helped along by an additional suggestion, which I offer tentatively. We are indeed a very uniform species if you count the totality of genes, or if you take a truly random sample of genes, but perhaps there are special reasons for a disproportionate amount of variation in those very genes that make it easy for us to notice variation, and to distinguish our own kind from others. These would include the genes responsible for externally visible "labels" like skin colour. I want to suggest that this heightened discriminability has evolved by sexual selection, specifically in humans because we are such a culture-bound species. Because our mating decisions are so heavily influenced by cultural tradition, and because our cultures, and sometimes our religions, encourage us to discriminate against outsiders, especially in choosing mates, those superficial differences that helped our ancestors to prefer insiders over outsiders have been enhanced out of all proportion to the real genetic differences between us. No less a thinker than Jared Diamond has supported a similar idea in The Rise and Fall of the Third Chimpanzee. And Darwin himself more generally invoked sexual selection in explanation of racial differences.
I want to consider two versions of this theory: a strong and a weak one. The truth could be any combination of the two. The strong theory suggests that skin colour, and other conspicuous genetic badges, evolved actively as discriminators in choosing mates. The weak theory, which can be thought of as leading into the strong version, places cultural differences, such as language and religion, in the same role as geographical separation in the incipient stages of speciation. Once cultural differences have achieved an initial separation the groups would subsequently evolve apart genetically, as if geographically separated. An ancestral population can split into two genetically distinct populations only if given a head start by an initial accidental separation, usually assumed to be geographical. A barrier such as a mountain range reduces gene flow between two populated valleys. So the gene pools in the two valleys are free to drift apart. The separation will normally be abetted by different selection pressures; one valley may be wetter than its neighbour, for instance. But the initial accidental separation, which I have assumed to be geographical, is necessary.
There is controversy here. Some people think the initial separation has to be geographical, while others, especially entomologists, emphasise so-called sympatric speciation, meaning that the initial separation, whatever it is, is not geographical. Many herbivorous insects eat only one species of plant. They meet their mates and lay their eggs on the preferred plants. Their larvae then apparently "imprint" on the plant that they grow up eating, and they choose, when adult, the same species of plant to lay their own eggs. So if an adult female made a mistake and laid her eggs on the wrong plant, her daughter would imprint on that wrong plant and would, when the time came, lay her eggs on plants of the same wrong species. Her larvae then would imprint on the same wrong plant, hang around the wrong plant when adult, mate with others hanging around the wrong plant and eventually lay their eggs on the wrong plant.
In the case of these insects, you can see that, in a single generation, gene flow with the parental type could be abruptly cut off. A new species is theoretically free to come into being without the need for geographical isolation. Or, another way of putting it, the difference between two kinds of food plant is, for these insects, equivalent to a mountain range or a river for other animals. I am suggesting that human culture - with its tendency to distinguish between in-groups and out-groups - also provides a special way in which gene flow can find itself blocked, which is somewhat analogous to the insect scenario I have just outlined above.
In the insect case, plant preferences are handed down from parent to offspring by the twin circumstances of larvae fixating on their food plant, and adults mating and laying eggs on the same food plants. In effect, lineages establish "traditions" that travel longitudinally down generations. Human traditions are similar, if more elaborate. Examples are languages, religions and social manners or conventions. Children usually adopt the language and the religion of their parents although, just as with the insects and the food plants, there are enough "mistakes" to make life interesting. Again, as with the insects mating in the vicinity of their preferred food plants, people tend to mate with others speaking the same language and praying to the same gods. So different languages and religions can play the role of food plants, or of mountain ranges in traditional geographical speciation. Different languages, religions and social customs can serve as barriers to gene flow. From here, according to the weak form of our theory, random genetic differences simply accumulate on opposite sides of a language or religion barrier, just as they might on opposite sides of a mountain range. Subsequently, according to the strong version of the theory, the genetic differences that build up are reinforced as people use conspicuous differences in appearance as additional labels of discrimination in mate choice, supplementing the cultural barriers that provided the original separation.
Learned differences in language, religion and social customs notoriously provide labels for prejudice and discrimination. So, even more obviously, do genetic differences in colour. Could the first category have been implicated in the evolution of the second?