I propose to resist the temptation to do any of this. I do not know the future, and my views on the morality of cloning humans, or germ-line engineering, or any other topic, are neither so deeply considered nor so unique as to warrant public exposure – a reticence born not of cowardice, but rather of courtesy, or so I like to think. Instead I will end this book, which has been all about the many things that we know about the construction of the human body, with some thoughts on what we do not know and what we – or at least I – would like to.
I would like to know about variety. Most of this book has been about the rare mutations that damage the body. If I have mentioned variety, I have done so only in passing. By variety I mean the normal variation in human appearance and attributes that we see in healthy people around us. I mean the variety that can be found within the smallest Scottish hamlet, with its brown-, green- and blue-eyed inhabitants. But I also mean the differences in form between populations of people who live near to each other, but are somehow distinct: short pygmies versus taller Bantu farmers, for example. And I also mean the differences in skin colour, hair curliness and eye shape that distinguish – more or less – people who originate from different continents. One of the things, then, that I want to know about is race.
Race has long been under siege. Among scientists, geneticists have led the assault. Their attack has been predicated on two empirical results that have emerged from the study of patterns of genetic variation across the globe. The first was the discovery that most of the variety so abundantly visible in our genomes does not divide humanity along lines that correspond to the races of traditional and folk anthropology. All genes come in different variants, even if most of those variants are ‘silent’ and do not affect the structure of the proteins they encode. Inevitably, some variants are more common in some parts of the world than others. But the ubiquity and rarity of most variant genes across the globe do not correspond to traditional racial boundaries. Racial boundaries are usually held to be sharp; gene variant frequency changes are generally smooth. Changes in variant frequencies are also inconsistent between one gene and another. If there are lines to be drawn through humanity, most genes simply don’t show where they should go.
The second discovery that caused, and causes, geneticists to doubt the existence of races is the ubiquity of genetic variation within even the smallest populations. About ?5 per cent of the global stock of genetic variation can be found within any country or population – Cambodians or Nigerians, say. About another 8 per cent distinguish nations from each other – the Dutch from the Spanish – which leaves only a paltry 7 per cent or so to account for differences between continents or, in the most generous interpretation of the term, ‘races’. To be sure, there are genetic differences between a Dutchman and a Dinka, but not many more than between any two natives of Delft.
These facts about human genetic variation have been known since the 1960s. In each decade since then they have been confirmed, with ever more lavish quantities of data, using ever more sophisticated means of finding and analysing human genetic variation. In the 1960s genetic variation was studied by examining the migration of variant proteins on gels; today it is studied by sequencing entire genomes. Generations of scientists have expounded these results much as I have here – and asserted that, as far as genetics is concerned, races do not exist. They are reifications, social constructs, or else they are the remnants of discredited ideologies.
Most people have remained unconvinced. They have absorbed the message that races are, somehow, not quite what they used to be. Far better, then, to avoid the word and substitute ‘ethnicity’ or some similar term that comfortably conflates cultural and physical variety. For some, the persistence of the idea of race is a sign of racism’s tenacity. I doubt that this is true. Instead I suspect that the reason the lesson of genetics has been so widely ignored is that it seems to contradict the evidence of our eyes. If races don’t exist, then why does a moment’s glance at a stranger’s face serve to identify the continent, perhaps even the country, from which he or his family came?
The answer to this question must lie in that 7 per cent – paltry though it is – of global genetic variation that distinguishes people in different parts of the world. Seven per cent is a small part of global genetic variation, but it is large enough to imply the existence of hundreds, perhaps thousands, of genetic polymorphisms that are common, even ubiquitous, on one continent but rare, or even absent, on another. In recent years some geneticists have begun searching for such variants. The variants are known as AIMs or ‘Ancestry Informative Markers’ – so called because they can indeed tell you roughly where your ancestors came from, and even sort them out if – the case for so many of us – they came from several different places. The search for AIMs, which initially focused on Africans and Europeans but is already being extended, is prompted by the hope of identifying the genetic basis of several diseases, among them type 2 diabetes, the risk of which differs among Africans and Europeans.
Many AIMs have already been found. For some of them, the reasons for their presence on one continent but absence on another is readily apparent. One variant of the FY gene is ubiquitous in Africans but extremely rare among everyone else. The African variant is odd insofar that it prevents the protein that FY encodes from being made. Everyone else makes the protein, though its exact form can vary too. The FY protein is a growth-factor receptor found on blood cells, one that the malaria parasite seems to use as well, and its absence in Africans is almost certainly the result of long-standing natural selection for resistance to the disease. The absence of FY in Africans and its presence everywhere else has been known for decades. Many other differences are now being found – although they are usually not as dramatic as FY’s. No one knows what most AIMS do or why they are there.
Somewhere among all those AIMs, however, will be the genes that give a Han Chinese child the curve in her eyelid and a Solomon Islander his black-, verging on purple-, coloured skin. Among them, too, will be the genes that affect the shape of our skulls. Skull measuring has a long history in anthropology. One of the first really assiduous skull measurers was a Dutchman, Petrus Camper, who in the 1700s invented the ‘facial angle’ – essentially an index of facial flatness. In his most famous diagram, Camper shows a series of heads and skulls – monkey, orangutan, African, European, Greek statue – with ever-declining facial angles. Camper himself was no racist. In his writings he emphasised repeatedly the close relationship between all humans no matter what their origins. ‘Proffer with me,’ he urged in 1764, ‘a fraternal hand to Negroes and recognise them for veritable descendants of the first man, to whom we all look as our common father.’ To which he added that the first man may have been white, brown or black, and that Europeans are really just ‘white Moors’ – and did so at a time when Linnaeus was carving up our species.