Human beings evolved from ape-like ancestors. The chimpanzee has almost identical genetic make up as humans. However, there is disagreement about the details of the progressive changes and the dynamic causes underlying evolution.

The human family first appeared in Africa about 5-6 million years ago. A second event, the migration out of Africa, occurred close to 2 million years ago. Until 30,000 years ago the fossil skulls found in Africa, Asia and Europe show a lot of anatomical differences. This is taken as evidence of several human species coexisting as a result of adaptive radiation of the primary human African stock. This is the 'out of Africa' hypothesis that says that modern humans evolved in an isolated population about 150,000 years ago with its descendants subsequently moving into the rest of the world. Almost certainly, everyone in the world today is a descendant of just one of these several populations, who in their inexorable spread across the world caused the extinction of species of humans who were like us but were not us. Some 40,000-50,000 years ago, a group of Middle Eastern people developed a type of tool that seems to have precipitated a radical expansion of the human mind and a new way of thinking about the environment, particularly the use of tools for survival. These pre-agricultural people developed the Aurignacian episode of cultural ecology.  They lived perhaps 2,500 generations ago.  The principal technologies were the use of fire and a relatively simple kit of stone flake tools. This tool kit was the product of nearly 2.5 million years of development.

Fewer than 500 generations later Homo sapiens had become something more than merely a large, common primate. It took only an eyeblink of evolutionary time. We, the generations who share the planet today, are facing a challenge to innovate on a level that may be as profound as the achievement of our distant ancestors. But we do not have 500 generations' worth of time to accomplish the task. It has been said that, depending on the degree of misery and biological impoverishment that we are prepared to accept, we have only one or perhaps two generations in which to reinvent a survival kit to sustain a new post-industrial cultural ecology.