Читать книгу The Times History of the World - Richard Overy - Страница 9

By 10,000 years ago, humans had colonized almost the whole of the habitable world. It was an achievement made in the face of the last of a series of Ice Ages, when vast sheets of ice periodically advanced and retreated. The human species today is the product of this long process of adaptation to the varied conditions of the Ice Ages.

There have been eight Ice Ages in the last 800,000 years, each interspersed with warmer periods from 30,000 to 10,000 years known as interglacials, brief and extreme parts of this cycle. The Ice Ages were periods of exceptional cold away from the equator. Ice sheets advanced across the frozen wastes of the northern hemisphere as temperatures fell by up to 15 degrees centigrade. With so much of the earth’s water locked into the ice sheets, sea levels fell by up to 150m (500ft). As they did so, land bridges appeared, linking many major land areas and present-day islands into larger continental land masses.

Equatorial regions were also affected: as rainfall diminished, half the land area between the tropics became desert. With each advance of the ice, the plants and animals of the northern hemisphere withdrew to warmer latitudes. As the ice retreated, so they moved northwards again. Humans, too, must have migrated with these changing climates. Yet despite the extremes of cold, the human species continued to develop, spreading from its original African homeland to east and southeast Asia and to Europe. Mastery of fire and the invention of clothing were crucial to this achievement, as were new social and communication skills.

ICE AGE HUMANS

The height of the last Ice Age or LGM (last glacial maximum) was reached about 20,000 years ago. As the ice expanded, human populations contracted into a small number of more favourable habitats. Across almost the whole of the Eurasian landmass between the ice to the north and the deserts to the south, from the glacial cul-de-sac of Alaska to southern France, productive grasslands and steppes were created. Rich in seasonal grasses, they sustained large herds of mammoth, bison, horse and reindeer, all of them important food sources for Palaeolithic (the period of the emergence of modern man, about 2.5–3 million years ago to 12,000 BC) hunters.

Much the same sort of habitat seems to have developed in North America. By the time modern humans migrated there about 15,000 years ago, the rolling grasslands were teeming with animal life: giant bison with a six-foot horn spread; towering beaver-like creatures called casteroides; camels; ground sloths; stag moose; two types of musk-oxen; several varieties of large, often lion-sized cats; mastodons; and three types of mammoth. So effectively did the new human population hunt them that by about 10,000 years ago almost all of them were extinct, including the horse, re-introduced to the New World only by Europeans following in the wake of Columbus.

South of the Eurasian mammoth steppe lay an extensive zone of drier conditions. Indeed parts of the Sahara, the Near East and India became almost entirely arid, forcing their populations along permanent watercourses such as the Nile. Similar patterns of settlement are found in Australia, where cemeteries discovered along the Murray River bear marked resemblances to those along the Nile.

Modern humans were late arrivals in western Europe, replacing Neanderthal populations only from about 35,000 years ago. Yet the new communities developed remarkable levels of cultural expression. In southwest France, the Pyrenees and northern Spain, hundreds of caves decorated with paintings of symbols and animals have been discovered, evidence of a rich cultural tradition.

By 12,000 years ago, the last Ice Age was drawing to a close. As temperatures rose, vegetation spread and animals re-colonized the cold northern wastes. With them went hunters and gatherers. By 10,000 BC in Central America and the Near East, people had begun to move beyond their existing resources and to investigate new ways of producing food and manipulating plants and animals in the first experiments in farming.