Steve Jones - The Language of the Genes

Those African farmers and their European counterparts no doubt experienced social unrest as they gave up hunting to move to a more productive but perhaps less enjoyable way of life. However, any romantic view of a harmonious past when contented foragers shared their food is a hunger for a nonexistent Golden Age. Virgil, in the Georgics, mourns for a time when 'No fences parted fields, nor marks nor bounds,/ Divided acres of litigious grounds.' His plaints over a happier past may have been shared by the early farmers as they mourned the glorious times when they hunted food rather than growing it. Whatever the truth, the origin of agriculture marked the end of an economic system based on individual effort which lasted for nine tenths of history. With farming, Eden had been left forever; and politics began.

Adam and Eve's children were a worry to their parents. Their eldest, Cain, is best known for having killed his brother Abel. He has another distinction. Just one generation after the expulsion from Eden he became the first capitalist. As the Old Testament says, he was the earliest to 'set bounds to fields'. By so doing he erected barriers among the peoples of the world. Frontiers have driven society, history, and genes ever since.

No doubt the idea which came to Cain struck the first farmers as well. Ownership of land was born with agriculture. The process can be seen today as hunter-gatherers give up the old social order. The Kipsigis of Kenya moved to a settled existence as maize farmers in the first years of the twentieth century. Great inequalities soon appeared. When harvests were bad the poor starved while the rich grew fat. Competition among males to gain a mate increased and there was a new campaign in the battle of the sexes. Those who owned productive land had far more children than did those with none. The farming genesis was when class began. From Mycenae to ancient Chile there emerged a difference in height and health between the rich, interred with their ornaments, and the rural poor, buried in penury.

The first farmers soon argued about who was to grow what and where. It did not take long for property to pass into fewer hands and for society to evolve into the system of competing tribes that persists today. Any barrier, be it a mountain, a frontier, or an inability to understand, which stops peoples from meeting and mating will cause them to diverge. All over the world, genetic changes mark the divisions — the bounds to fields — between ancient societies.

Even so, politics is a new clement in the evolutionary equation. Genetics suggests that what we see as history, the struggles between nations, is a recent event. From the Old Testament to Meirt Kampf, historians have seen conquest as the key to the peoples of the world. In the turbulent years after the First World War, the League of Nations tried to define just what a 'nation' might be. The best they could come up with was 'a society possessing the means of making war'. Over the past millennium, most great nations have spent half their time at war; but marauding states have shaped biological history only in the past few thousand years. Before then, people and their genes moved by gradual diffusion or by migration into an empty land, rather than by the defeat of one social entity by another.

In many parts of the world the earliest farms, and the first settled societies, were by rivers in an arid landscape. Such rivers (the Nile most of all) often flood, to leave fertile silt as they recede. Modern tribal farmers who use the land left bare by the departing waters of the Senegal River obtain a return on labour of fifteen thousand per cent: for every calorie of effort they put in they get a hundred and fifty back as food. This compares with a return of around fifty to one for the most efficient modern fields.

The return on the flood plain is enormous but, like the stock market, unpredictable. For the locals, life, as on Wall Street, could be bumpy. The flooding of the Nile has been noted since AD641. The records reveal a hundredfold difference in the area of land submerged from year to year. Some years are excellent but others are dry and disastrous. In today's Senegal, with its equally capricious rivers, this has produced a rigid pecking order. Some families always have access to the floodlands even when the area inundated is small. Others are allowed to grow crops only when the river has risen high and covered large tracts of ground. In dry years they have to find food elsewhere, and in earlier times that meant a return to hunting. Perhaps the earliest settled communities developed, not to increase efficiency but to manage risk. A wild free-for-all for the best land in a bad year would have been dangerous and expensive. Society evolved as a way of coping with uncertainty.

Ten thousand years ago the Natufians, the descendants of the cultivators of the Jordan Valley, had built villages with timber houses. Within two millennia Mesopotamia contained much larger settlements. It took but a few centuries for civilisation to advance to such an extent that such places were surrounded by walls, ditches and watchtowers. Warfare had begun to play the part which it has retained ever since. Farmers were forced from their hamlets by land degradation and the pressure of numbers. In Mesopotamia they moved into the hot and dry plains away from the Tigris and Euphrates rivers. Soon, the earliest city-states began, perhaps because of the need to organise which began with the irrigation. For the first time humanity was divided by political rather than physical barriers. The genes of today show that, since then, bigotry has been as effective an obstacle as has geography.

Capitalism was helped by technology. The bones of six-thousand-year-old horses at Sredny Stog in the Ukraine have broken teeth, as if they were controlled by bits. A horse increases mobility and helps people to work together to steal from others. Its power is seen in the success of a few dozen Spaniards in the conquest of the Inca and Aztec Empires and of the Mongols in taking over Hungary. Soon after the appearance of horsemen the civilisations of East-ern Europe built defensive walls around their towns. Within a few years their societies had collapsed.

By 3600 BC Mesopotamia contained great cities. Uruk had ten thousand people and within a millennium that number had increased fivefold. Its growth was due in part to warfare. Scores of villages were abandoned by their people, who moved to the new cities. The Sumerian city states, the first organised political entities, were the source of writing and of wheeled transport. They hud a priesthood and an aristocratic caste, and a dispossessed mass. Their decline was hastened by mismanagement. With irrigation, the soil became salty and in the last years of Suineria crop production dropped to a third of its peak. These, the first nations, were overcome by one of the first empires, that of the Akkadians, who invaded from the north.

Other cities came to an end because of bad planning. The ruins of Petra, in Jordan, are today surrounded by miles of arid desert. The evidence of its decline is preserved in an unusual way. Hyraxes (small mammals about the size of a guinea pig) live in communal mounds. They have the singular habit of cementing their homes together with urine, which dries to form an unpleasant but effective glue. It also preserves the seeds upon which their ancestors fed. At its height, Petra was surrounded by forests of cedar and pine. These were burned. Grassland followed and this was much farmed. Within a few centuries, the desert had taken over. No doubt, the inhabitants of Petra in its last days fled the city, taking their genes with them.

No one has studied the patterns of genes in today's Iraqis or Jordanians (some of whom may be direct descendants of the people of Petra). When they do, the genetic relics of the first cities may be revealed. However, other forgotten societies — and the divisions between them — have left biological traces which persist to the present time.