Wednesday, March 14, 2007

Evolution and the Pleistocene

The Pleistocene Epoch, commonly referred to as the Ice Age, was just the latest of many glacial periods in our planet's history. Stretching from 2 million years ago to 10 thousand years ago, this Epoch was characterized by four glacial advances and three warm, interglacial periods; some climatologists believe that the Holocene, the Period in which we live, is just another respite from the cold.

The unstable climate of the Pleistocene likely had a dramatic influence on evolution over the past 2 million years, forcing rapid adaptations and favoring intelligent creatures. Homo erectus appeared in Africa at the dawn of the Pleistocene and reached southeast Asia within 100 thousand years; not equipped to deal with the cold, he stayed south of the periglacial region, migrating along the southern coast of Asia. Neandertals diverged from the human lineage some 200,000 years ago, moving northward into western Asia and Europe. Humans did not appear until 125,000 years ago but, by the end of the Pleistocene, had spread to every continent except Antarctica. Low sea levels, resulting from glaciation, facilitated their dispersal.