As some bands grew in number, they had to roam farther from their usual hunting- and-gathering grounds to find enough food. Each new generation expanded the band's migration pattern. Some experts believe that just two or three miles (3.2 to 4.8 km) were added every 20 years the average length of an early person's life.
By this slow process, humans began to spread throughout the world. It probably took hundreds of generations thousands of years to do this!
For a long time, Homo sapiens lived only in Africa. Gradually, some bands began moving farther north as they hunted and gathered. In time, bands had traveled across the dry grasslands of the Sahara, into the Nile Valley, and then into southwestern Asia. This movement of people set the stage for the settlement of the entire world. Between 12,000 and 100,000 years ago, the descendants of the earliest African bands spread to Asia, Europe, Australia, and finally to the Americas.
Much of this settlement was made possible by the last Ice Age. An Ice Age is a long period of bitter cold. In the distant past, the Earth had several Ice Ages. The last Ice Age began about 115,000 years ago and ended about 10,000 years ago.
During each Ice Age, huge sheets of ice called glaciers covered parts of the Earth's surface. Because much of the ocean was ice, sea level was nearly 300 feet (90 m) lower than it is today. This meant that there was more dry land than there is now. Land bridges connected some islands and continents. Early people were able to use the land bridges to travel between places that are now divided by water.
Some archaeologists believe that early hunters and gatherers first set foot in southwestern Asia about 100,000 years ago.
There they found herds of gazelle and deer. Following these herds, generation after generation of early people spread out in many directions.
By about 65,000 years ago, hunters and gatherers had traveled all the way east in Asia to the land now known as China. Later generations followed land bridges to what is now Indonesia. From there, men, women, and children paddled log rafts across the open ocean to Australia. People probably reached this continent by 50,000 years ago.
Early people also moved in other directions. About 40,000 years ago some groups of people spread from southwestern Asia into Europe. Others migrated to the northeast, following herds of wild animals. They reached what is now Siberia in Russia about 35,000 years ago. There they faced a harsh environment as they adapted to life in the tundra, or large treeless plains found in Arctic regions. Archaeologist Goran Burenhult describes early life in Siberia's tundra this way:
The hunters who inhabited these immense, frozen, and treeless expanses had to cover vast territories in pursuit of game and other food. There were few caves and rock shelters for protection, so they had to build huts that could withstand the severe cold.
The bitter cold of the tundra made life difficult for the early people of Siberia.
They needed to keep fires burning almost all the time to stay warm. Also, their clothes had to fit snugly to prevent them from freezing. The huts they built were made of sod a layer of soil with grass growing from it and mammoth bones. Mammoths were large, hairy elephants with long tusks. Early people used mammoth bones not only for building but also for fuel and tools. Other parts of the mammoth gave the early Siberians food to eat and hides for clothing.
The migration of early people did not stop in Siberia. Bands moved east from Siberia over a land bridge that crossed the Bering Strait, a shallow sea between Asia and North America. Between 12,000 and 40,000 years ago, early people moved into North America. Eventually some hunter- gatherers reached South America.
What effect did the movement of early people have on the world?
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