Mutants (38 page)

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.

Sadly, Camper’s iconography spoke louder than his words, and his diagram with its implicit demonstration of a hierarchy from ape to Apollo (with Africans rather closer to apes than to gods) became a staple of nineteenth-century anthropology. There is no need to recap and critique the craniometric studies carried out in the nineteenth and early twentieth centuries that sought to demonstrate that one subset of humanity was more or less intelligent than another – others have done so with a thoroughness that their scientific influence scarcely merits. But it is
worth noting that modern physical anthropologists remain keen on describing skull shape, though nowadays they tend to do so with 3-d laser scanners and multivariate statistics. They find, perhaps unsurprisingly, that for all the variety within populations, people from different parts of the world have different-shaped heads.

Much as Camper claimed, the jaws of sub-Saharan Africans
do
protrude, on average, further from their foreheads than do the jaws of Europeans – an attribute known as ‘prognathism’. Melanesians and Australian Aborigines are also more prognathic than Europeans.
Contra
Camper, however, this does not make African (or Aborigine) skulls more like ape skulls than European ones. The facial angle is a rather crude way of capturing an exceedingly complex aspect of skull shape. It does not discriminate between different ways of being prognathic. A chimpanzee has a high facial angle because its whole face and forehead slope; Africans and Aborigines have slightly higher facial angles than Europeans because of a jut in the jaw alone. Besides, Europeans do not even have the flattest faces. That honour – if honour it is – must go to the Inuit of northern Canada.

Human skulls are wonderfully diverse. The Inuit are also notable for the largeness of their eye orbits and the massiveness of their cheekbones. Compared to everyone else, the Khoisans of southern Africa have bulging foreheads (frontal bossing); Australian Aborigines have massive brows (supra-orbital ridges); some sub-Saharan Africans have widely set eyes (large inter-orbital distances); Andaman Islanders (negritos) have small, round skulls – the list of differences could be extended
indefinitely. Few of these differences are absolute. Just as most of the variance in gene frequency is found within, rather than among, populations (nations, continents), so too is most of the variance in skull shape. And the differences among populations are all subtle. Australian Aborigines and Inuit differ in prognathism by only 6 per cent. Small differences, then, but differences that, given the attention we devote to each other’s faces, strike us immediately.

V
ARIATION IN HUMAN SKULLS
: L
EFT TO
R
IGHT
: A
USTRALIAN
A
BORIGINE
, C
HINESE
, E
UROPEAN AND
K
HOISAN
. F
ROM
A
RMAND DE
, Q
UATREFAGES
18822
Crania ethnica: les cranes des races humaines.

My claim that we will soon be able to identify the genes responsible for all this diversity in skull shape suggests an important question: namely, do such genes exist? In 1912 the American anthropologist Franz Boas set out to demonstrate that they do not. A humane and tolerant man, he was an implacable opponent of those who sought to make invidious distinctions between humanity based on the shapes of their skulls. The following
passage, taken from a serious anthropological article written in 1905 by a German dentist called Rose, gives a flavour of what he was up against: ‘The long heads of German descent represent the bearers of higher spiritual life, the occupants of dominant positions, to which they are destined by nature, the innate defenders of the fatherland and the social order. Their whole character predetermines them to aristocracy.’ And so on, to the detriment of the more democratically minded and un-German ‘round heads’.

The ‘long’ and ‘round’ heads refer to the value of the ‘cephalic index’, the ratio of skull breadth to width (expressed as a percentage, long heads or dolichocephalics have a cephalic index below seventy-five, while round heads or brachycephalics have a cephalic index above eighty; mesocephalics are somewhere in between). Noting that the immigrants who arrived at Ellis Island – Bohemians, Slovakians, Hungarians, Italians, Scots and Eastern European Jews – varied somewhat in their cephalic indexes, Boas asked whether these differences were due to genetic (to use his terminology, ‘racial’) or environmental causes. He reasoned, soundly, that if the skulls of the American-born
children of all these various groups were more similar to each other than those of European-born children, then environment rather than ancestry must be the cause of the differences. Boas measured some thirteen thousand heads – a vast undertaking that left him, in the absence of computers, overwhelmed by numbers. Nevertheless, he managed to produce a graph that seemed to show that the cephalic indices of the US-born children of Sicilians and Eastern European Jews (both rather dolichocephalic to begin with) were, indeed, converging. It was a case of new heads for the New World.

Boas’s study dealt a near-fatal blow to craniometry. Over the last ninety years it has been cited innumerable times – not least by the late Stephen Jay Gould – as proof that skull shape is ‘plastic’, that is, caused by non-genetic differences. Boas, however, was wrong. His data have recently been comprehensively re-analysed using modern statistical techniques. The skulls of American-born children do indeed differ from those of their parents, but they do so inconsistently. Indeed, had Boas chosen to compare the children of Scots and Hungarians, rather than those of Sicilians and Eastern European Jews, he could have shown that America causes skulls to diverge rather than converge in shape. But he was wrong in a deeper sense than this. Re-analysis of his data also shows that the changes in skull shape caused by American birth, whatever their direction, are trivial compared to the differences that remain and that are due to ancestry and family – or, to put it more succinctly, to genes. Indeed, looking beyond European immigrants, this is hardly surprising. Forensic anthropologists in the United States and Britain are quite adept at telling
whether a given skull, perhaps evidence of some foul deed, once belonged to someone of African or European ancestry. That they can do so after decades, even centuries, of co-existence, not to mention generous amounts of admixture, suggests that our differences are not, as is often said, merely skin deep, but extend to our skulls – if not to what they contain.

So, genetic differences exist among all sorts of people. Should we try to find out what they are? Many scientists think not. Some find it enough to dismiss such physical diversity as exists among human populations as ‘uninteresting’ – not worthy of study. Others concede that it may be interesting, but that it should not be studied, since even to contemplate doing so is to engender social injustice. They fear a revival of not merely racial, but racist, science.

For my part, I should love to know the genes responsible for human diversity; the genes for the differences – be those differences between men and women who live in the same village or those who have never trodden on each other’s continents. In part this is simply for the pleasure of knowing. This the pleasure that comes from looking at Gabriel Dante Rossetti’s painting
La Ghirlandata
and knowing that his model, Alexa Wilding, had two loss-of-function MC1R mutations that gave her such glorious red hair. This pleasure of knowing is partly that which all science gives, but to which is added the pleasure that comes from understanding the reason for something that has been hitherto at once familiar but completely mysterious.

The view that human diversity is dull seems to me excessively Olympian. After all, if population geneticists have ignored
human variety, they have for decades lavished their (seemingly inexhaustible) energies studying variety in the colours of garden-snail shells and the number of bristles that decorate the backs of fruit flies – problems that are intellectually much like those presented by human variation.

The claim that human genetics is morally dangerous is a more serious one. One can certainly, given the history of racial science, see where such a claim originates. Nevertheless it is misplaced. Reasonable people
know
that the differences among humans are so slight that they cannot be used to undermine any conceivable commitment to social justice. ‘Human equality,’ to borrow a slogan of Stephen Jay Gould’s, ‘is a contingent fact of human history.’ What is true, however, is that as long as the cause of human variety remains unknown – as long as the 7 per cent of genetic variance that distinguishes people from different parts of the world remains obscure – there will always be those who will use that obscurity to promote theories with socially unjust consequences. Injustice can sometimes be the consequence of new knowledge, but more often – far more often – it slips in through the cracks of our ignorance.

Perhaps the most compelling reason that we should once again turn our attention fully to the study of human physical diversity is that it is disappearing. In South-East Asia the negritos, those enigmatic pygmy-like people, are in decline. They are hunter-gatherers. Overrun by Austronesian-speaking farmers in the Neolithic, they mostly persist on remote islands. Now, modernity threatens. On Lesser Andaman, the remaining Onge live in reservations. On Greater Andaman, a few hundred
Jarawas survive by virtue of having fended off the curious with bows and arrows (in the last fifty years they have killed or injured more than a hundred people), but they too have now emerged from the forest, attracted by baubles offered by Indian officials. It is feared that they will soon succumb to tuberculosis, measles and culture shock as their predecessors have.

They are only the latest casualties of Austronesian and European (not to mention Chinese, Bantu and Harappan) expansion. In 1520 Ferdinand Magellan, arriving at the straits that today bear his name, reported the existence of a race of giants that lived in the interior of Tierra del Fuego. He called them the
Pataghoni
, after a giant in a Spanish tale of chivalry. Subsequent travellers embroidered the account; by 1767 these giants, a wild and brutal people, had grown to about three metres (ten feet) tall. Today, the giants of Tierra del Fuego are as forgotten and fantastical as Pliny’s Arimaspeans. And yet the
Pataghoni
existed. They called themselves the Selk’nam or Ona, and they had an average adult-male height of 178; centimetres (five feet ten inches) – giant, then, but only to sixteenth-century Spanish sailors. But if their stature was not that remarkable, their skulls certainly are. They have a strength and thickness, a robustness, which other human skulls don’t, and this is true of their skeletons as a whole. Some photographs of the Selk’nam exist. They depict a handsome and physically powerful people who wore cloaks made from the pelts of the guanacos that they hunted on foot using bows as tall as themselves. Argentine sheep ranchers killed the Selk’nam off in a genocidal slaughter, and the last one died some time around 1920.