This is the story of people and the landscapes in which they lived—the actors and the stage—a story created largely without the benefit of a script and pieced together from fragments of disparate evidence brought to light by a formidable range of specialists. It is a narrative set in Eurasia covering some ten thousand years of human endeavour.

If we begin with the proposition that ‘history’ is the result of human action constrained and empowered by environment, then it follows that we need to understand something of the human animal and the imperatives hard-wired into the beast’s genetics, and we need to comprehend the landscape in all its ever-changing variety.

All living matter is governed by two desires: to feed itself and to reproduce its species. Humans share these desires but are more complex beings, differing from all other species in their intense acquisitiveness. This innate desire to acquire manifests itself in two forms: the passion to take ownership of commodities and the need to gather knowledge and information—to know. It is this inquisitiveness that has, over the millennia, drawn humans to explore every ecological niche on earth and to occupy most of them. It is, arguably, the one instinct that separates us from the rest of the animal kingdom.

To want to know what is ‘beyond’ is a natural human response. It must have been one of the prime incentives that drove the Lapita people to explore and settle the Pacific islands in the late second millennium bc, travelling across 6,500 kilometres of open ocean. It also lay behind Greek journeys into the Atlantic so vividly brought to mind by the third-century BC Greek writer Eratosthenes, who described how one could, in theory, sail from Iberia along the parallel to reach India. Strabo, who quoted him, reflected that ‘Those who have tried to circumnavigate the ocean and then turned back say that the voyage beyond the limit reached was prevented not through opposition or any constraint but through destitution and loneliness, the sea nevertheless permitting further passage.’

How many adventurers set out on the journey and how many returned? This sense of the ever-fascinating ‘beyond’ is brilliantly captured in classical Chinese painting with its successive horizons, each becoming paler with distance, enticing the viewer further into the landscape.

Inquisitiveness leading to travel may satisfy personal curiosity, but in many societies a voyage endowed the adventurer with renown. To return after a long journey with esoteric knowledge or exotic goods set the traveller apart: he held a power that other men did not, and story-telling about distant parts became an art. This was the very stuff of the heroic societies reflected in the works of Homer. When the unknown traveller Telemachus and his entourage arrived at the palace of Nestor, he was accepted, bathed, and fed without question, and only when the rules of hospitality had been observed could Nestor ask: ‘Who are you, sirs? From what part have you sailed over the highways of the sea? Is yours a trading venture; or are you cruising the main on chance, like roving pirates who risk their lives to ruin other people?’

Another incentive to travel was to acquire rare raw materials, the ownership of which gave enhanced status, partly for the inherent qualities of the goods and partly because they came from the world ‘beyond.’ Mesopotamian societies were passionate about the deep, rich blue of lapis lazuli quarried in the mountains of Afghanistan and the blood-red carnelian from India, while for the Chinese it was the subtle greens of jade from the fringes of the Taklamakan desert and elsewhere that made the stone desirable from the Neolithic period to the present day. Other commodities that feature large in our story include copper, horses, silks, and spices, all of which were rare, difficult to access, and therefore even more desirable. The essence of the matter was brilliantly summed up by the French historian Fernand Braudel when he wrote: ‘So we find that our sea was, from the very dawn of its protohistory, a witness to those imbalances productive of change which would set the rhythm of its entire life.’ Braudel was writing specifically about the Mediterranean, but he was reflecting on the fact that resources worldwide are very unevenly distributed and their redistribution sets up pervading rhythms that can reverberate across time. Recognizing these rhythms, usually characterized under the mundane terms ‘trade’ and ‘exchange,’ is a crucial part of the work of an archaeologist.

Prime Movers

A huge variety of factors drive social and economic development, but two in particular are rightly given prominence by archaeologists: demography and climate change.

All life forms have an innate compulsion to reproduce, and were they to do so unrestrained their populations would grow exponentially. It is only the environment they inhabit that imposes constraint because of its finite holding capacity. The relationship of human communities to the holding capacity of their territory is a highly complex matter and one difficult to approach archaeologically, but certain generalizations can be offered. If the population rises to unsustainable levels, there are various technological and social mechanisms that can be introduced. New methods of food production could be developed. For example, the cultivation of cereals and the domestication of animals could, in ideal circumstances, lead to greater and more assured yields. At a later stage productivity could be increased by intensification, such as by irrigation of the kind introduced in the valleys of the Tigris and Euphrates and the Yangtze. Animals could also be selectively bred to become more efficient meat or milk producers, and new methods of herding, using horses, could open up new pastures.

There are also social mechanisms available to relieve population pressure. Birth rate could be reduced by taboos of various kinds like advancing the age acceptable for marriage or, in extreme cases, requiring the sacrifice of the firstborn. Senilicide— removing the unproductive elderly—is another effective method for lessening the pressure on food resources. So, too, is warfare, which appears to be endemic to most societies and, if kept at a moderate level, can help to redress imbalances caused by a growing population. Equally common is outward migration, which may take many forms. At a modest level it may be little more than the social expectation that young men will move away from the home territory to establish new enclaves beyond. Mechanisms of this kind could account for the speed with which the practice of farming spread through the European peninsula in the sixth and fifth millennia. Similar imperatives lay behind the sending out of colonial expeditions by the Greek and Phoenician city states in the first half of the first millennium BC. Population pressure is said by the Roman author Livy to have been the reason why tens of thousands of Celts moved from a west central European homeland to the Italian peninsula and to the Carpathian basin and beyond in the fifth and fourth centuries BC. Population pressures may well have been one of the causal factors behind the westward advances of many steppe populations, from the Scythians in the eighth to the sixth century BC to the Mongols in the thirteenth century AD.

The other ‘prime mover’ that undoubtedly had a significant effect on human mobility was climatic change. The overall picture is of a gradual improvement of the climate from the end of the Last Glacial Maximum about 13,000 BC until 7000 BC, when the climate began to approximate to what it is today, but there was a final last return of icy conditions in the Younger Dryas phase, 10,800–9600 BC, which rendered many environments, already peopled, difficult for human occupation. Many writers see this as a crucial factor in forcing some communities to experiment with modes of food production, leading to the development of settled farming economies. But even after 7000 BC, when the world climate reached a degree of stability, there were fluctuations of sufficient magnitude to affect the more marginal regions, triggering the need for social and economic readjustments. This is particularly noticeable in the steppe.

While demographic and climatic factors might singly affect social systems causing local readjustments, occurring together they had the potential to exacerbate change on a regional or continental scale. Understanding the narratives of history then requires an understanding of the intricate dynamics between geography, climate, and human agency.