Darwin's Island (40 page)

The British Isles have a history of sexual 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, sexual 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 passed on his genes, and many of his fellows passed 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 sexually closer than they were. For every class 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
). 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 sex, 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 encompasses 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 class 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
Homo 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.

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
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.