They also grow cotton, from which they weave a coarse cloth.
The retreat of the ice caps (see Ice Ages) makes northern regions increasingly habitable both for large animals and for the humans who prey on them.
By 8000 years ago hunter-gatherers have moved up the eastern side of the continent into Newfoundland and the prairie provinces of Canada.
These are the very ancient Maya, and the relatively upstart dominant cultures of the time, the Aztecs and the Incas.
The original people of north America live in a wide range of environments.
When the melting ice submerges the bridge, about 10,000 years ago, these northeast Asians become isolated as the aboriginal Americans.
The Siberian hunter-gatherers probably make their way along the north coast of Alaska and down through the valley of the Mackenzie river.They are followed, about three centuries later, by the earliest civilization of south America - the Chavin culture of Peru.These two first American civilizations, in Mexico and Peru, set a pattern which will last for more than 2000 years.Dating from around 1200 BC, it is the achievement of the Olmec people.Their culture is contemporary with Mycenae and the Trojan War, with the spread of the Aryans through northern India and with the Shang dynasty in China.A succession of highly developed cultures, all strongly influenced by the traditions of their predecessors, follows in the same two limited regions of the continent - in central America (also known as Mesoamerica) and in the strip of land between the Andes and the Pacific.