ABSTRACT
Fossils in Africa provide the earliest evidence for the splitting off of a human branch of the ape family tree. Based on changes in their teeth and skulls, these fossils show a shift in the ways that these populations used the environment and in their social and feeding behaviors. By about four million years ago, humans were walking upright on two legs (bipedal orthogrady) and seeking a varied diet. By two million years ago, brains were bigger, teeth and jaws tended to be smaller, tools were better, and humans began to control fire. By about one million years ago, humans were all over the Old World. Our species, Homo sapiens, emerged in Africa between 200,000 and 100,000 years ago, and spread throughout the world. This expansion was made possible with better tools, but also better clothing, shelter, food production, and special behaviors and technologies that produced boats and domesticated animals. Culture and language helped these humans to share these innovations with other groups and to pass them on to future generations. As with previous human species, Homo sapiens shared the Earth with two or more other human species for most of its history. It is only in the last few tens of thousands of years that we have emerged as the “one and only” human species on the planet.
