Darwin's Island Part 9

In that great global coalescence, h.o.m.o sapiens h.o.m.o sapiens has evolved in just the same way as have other weeds. In other ways, man is quite unique: for he is the only animal that has escaped - or almost so - from the reach of evolution's pitiless laws of life and death. Natural selection has long been at work on our species, even if our ingenuity has mitigated its power, with far less response in our own line than in that of the chimpanzee. Now, in the nation in which the idea was invented - and, more and more, in the world as a whole - the process has slowed down and may soon stop. has evolved in just the same way as have other weeds. In other ways, man is quite unique: for he is the only animal that has escaped - or almost so - from the reach of evolution's pitiless laws of life and death. Natural selection has long been at work on our species, even if our ingenuity has mitigated its power, with far less response in our own line than in that of the chimpanzee. Now, in the nation in which the idea was invented - and, more and more, in the world as a whole - the process has slowed down and may soon stop.

I depress my first-year students with the statement that two out of three of them will die for reasons connected to the genes they carry (a vague claim, but good enough for undergraduates). Then I try to cheer them up by pointing out that had I given the lecture in Shakespeare's time, two out of three of them would, at the age of eighteen or so, be dead already. Even in the year of Darwin's birth, about half of all British newborns died before they reached their majority. Life in these islands has seen a real change for the better. An English baby born in the year of the millennium had a 99 per cent chance of surviving until 2021 and that figure continues to improve. j.a.pan does even better, and the United States rather worse, but most of the developed world has seen a revolution in the prospects of the young. In most countries, even those as poor as Ecuador, the death rate of children is less than, or no more than twice as high as, the British figure. Africa is, alas, a real exception. The death rate for under-fives is one in four in Sierra Leone and is almost as high in Angola and Liberia, while Swaziland has an overall life expectancy of just forty years, half that of j.a.pan. As a result, differences in childhood mortality still account for most of the globe's variation in life expectancy but, outside the continent where h.o.m.o sapiens h.o.m.o sapiens began, those differences have withered away. began, those differences have withered away.

Natural selection is very interested in the death of young people, for they have not yet pa.s.sed on their genes. It cares far less about the fate of the old - those over forty or so - for their s.e.xual lives are over and their relevance to evolution at an end. As a result, the great agent of change has lost a good part of its fuel. For most of history, the Grim Reaper was the master of man's biological fate. Now, he is taking a rest, and inherited differences in the ability to withstand cold, starvation, vitamin deficiency or disease no longer do much to power the evolutionary machine. Plenty of people still die for those reasons, but they do so when they are elderly and evolution no longer notices them.

The Darwinian examination has two parts. In the developed world, most people pa.s.s the first paper: they stay alive until they are old enough to have children. The second section is just as inexorable but has a wider range of marks, for any candidate for evolutionary success has to find a mate and reproduce. The more children they have, the better the prospects for their genes.

Females are limited in the number of offspring they can produce by the mechanics of pregnancy and child care, while males are free to spread their sperm to a mult.i.tude of partners, even if a certain amount of persuasion is needed first. As a result, males compete for the attention of females, while females must decide which males should be allowed in. s.e.xual selection depends on the same logic as selection on the ability to survive: on inherited differences, not in the chances of life or death, but in the number of young. The rule applies to humans just as it does to birds and flowers.

Both humans and peac.o.c.ks have more variation in male s.e.xual success than in female. Until not long ago, many societies contained a few satisfied libertines, outnumbered by a huge ma.s.s of frustrated men. The powerful have always taken their amatory chances when they arise. Henry VIII was a minor player in the marital stakes. The emperor in the Ch'I dynasty of China maintained a palace with several thousand women available for his amus.e.m.e.nt, while in tribal societies men with high status still have many more mates than do their humble (and often celibate) fellows. Mohammed bin Laden, father of Osama of that ilk, had twenty-two wives and fifty-three children (and in the year of Osama's birth he had six). His best known son had, last time they were counted, five wives and twenty-two children. Given the equal numbers of men and women at birth, plenty of his henchmen will be obliged to die, naturally or otherwise, without issue.

The British Isles have a history of s.e.xual inequality that makes even the antics of the founder of the Church of England look feeble. The evidence is in the Y chromosome, which marks male descent. It comes in a diversity of forms. In the majority of places most men have their own more or less unique model of their most masculine attribute. A fifth of the men of north-west Ireland, in contrast, share a more or less identical version of the Y chromosome - which means that they all trace ancestry from the same male.

In the glorious days of old Erin, s.e.xual inequality was rife. Lord Turlough O'Donnell, who died in 1423, had eighteen sons and fifty-nine grandsons. He was himself a descendant of the High Kings of Ireland, all of whom claimed a certain fifth-century warlord, Niall of the Nine Hostages, a man who once kidnapped St Patrick, as their common ancestor. The Y chromosome of Niall the hostage-taker has, thanks to his own exploits and those of his powerful male descendants, spread to thousands of today's Irishmen. The surnames fit, too, for men of the Gallagher, O'Reilly and Quinn families, all of whom claim descent from the High Kings, are most likely to bear the special Y chromosome. In Ireland, for many centuries, the mightiest male pa.s.sed on his genes, and many of his fellows pa.s.sed their days in glum celibacy and the demand for soldiers or priests occupied their energies instead.

Today's reproductive universe is quite different. Everywhere, the weak and the powerful - the poor and the rich - are s.e.xually closer than they were. For every cla.s.s in society, the average number of children has, thanks to technology, gone down. Natural selection cares naught for that, for the important figure is not the number of progeny, but the variation in how many children people have. That figure has shrunk. Five centuries ago in Florence, the upper crust had twice as many offspring as did the peasantry but now the Florentine poor have more than the rich and Britain is much the same (which worries the Daily Mail Daily Mail). The gulf has closed through restraint by the affluent rather than excess by the poor. A furtive exchange of information about birth control meant that rich families soon became smaller while those of the poor declined more slowly. Schools, too, are a powerful contraceptive. Everywhere, people with degrees have fewer children than those who drop out. As education spreads, the fertility imbalances will become smaller yet.

Inequality, in survival or in s.e.x, is an ore refined by natural selection to adapt existence to changing conditions. The differences in people's ability to stay alive and to have children can be combined in a single measure that shows just how much of that raw material is still available. Across the world the figure - the 'opportunity for selection' - is in steep decline. India tells the tale within a single country. The nation encompa.s.ses a range of cultures from tribal hill-peoples to affluent urbanites, together with vast numbers of peasant farmers whose lives are rather like those of Europeans a few centuries ago. The figures of life, death and birth when put together show that natural selection has lost nine-tenths of its power in India's middle cla.s.s when compared with the people of the tribes. The same is true when we compare the modern world with that of the Middle Ages and - to a lesser degree - even with that of the Victorians.

As Charles Darwin himself insisted, evolution is not a predictive science. Natural selection has no inbuilt tendency to improve matters (or, for that matter, to make them worse). For h.o.m.o sapiens, h.o.m.o sapiens, some nasty surprises no doubt lurk around the corner. Some day, evolution will take its revenge and we may fail in the struggle for existence against ourselves, the biggest ecological challenge of all. some nasty surprises no doubt lurk around the corner. Some day, evolution will take its revenge and we may fail in the struggle for existence against ourselves, the biggest ecological challenge of all.

Whatever the future holds, the bicentennial of his birth marks a new era in the biology of our planet. The changes are not limited to the rain forest, or the coral reefs, or the teeming tropics, but are hard at work on Darwin's own island and on the people who live there. From Shrewsbury to the Galapagos and from worms to barnacles to human beings, there has been a triumph of the average. The Earth is, as a result, a far less interesting place than it was when HMS Beagle Beagle set sail. Whether it becomes even less so - and whether it survives at all - depends on the talents of the only creature ever to step beyond the limits of Darwinian evolution. set sail. Whether it becomes even less so - and whether it survives at all - depends on the talents of the only creature ever to step beyond the limits of Darwinian evolution.

Also by Steve Jones

The Language of the Genes

In the Blood

Almost Like a Whale

Y: The Descent of Men

The Single Helix

Coral: A Pessimist in Paradise