ABSTRACT
Paleoanthropologists are engaged in a great debate over which of two models more accurately describes how humans came to occupy the entire Earth. Both models recognize that there were two great migrations out of Africa; and they agree that the first, between 1 million and 700,000 years ago, took Homo erectus to the limits of Europe and Asia. The first theory, dubbed the "out of Africa" model, asserts that we are all descended from a common ancestor, a species that originated in a single place in eastern Africa about 200,000 years ago. The second model is called the "multiregional model". It holds that humankind's ancestors arose at different places around the world and gradually blended themselves with other species with which they came into contact, producing thereby the mix of traits that we label as "modern human". Thus, local populations of Homo erectus in Europe, Asia, and Australia evolved toward Homo sapiens with a significant gene flow between them.
