Evidence Suggests Climatic Changes Spurred Evolution

Article excerpt

Off the coast of Africa, a Columbia University expert has discovered the first detailed evidence of ancient climatic changes that may have spurred human evolution.

No one knows for certain what forced humanity's remote ape-like ancestors to forsake the trees they called home, why some prehuman species surpassed others, or why primitive human ancestors migrated out of their African homeland. There are, experts say, as many theories as there are fossils.

But new research suggests that weather may be at the root of the human family tree.

An analysis of ocean sediments made public earlier in October shows that in the past 3 million years the cradle of humankind in East Africa was rocked three times by abrupt cycles of colder, drier climate. Each cycle of change coincided with the demise of some prehuman species and the development of those who became the forebears of modern humanity.

The finding by climate authority Peter deMenocal at Columbia's Lamont-Doherty Earth Observatory is a "wonderful development" that buttresses a controversial theory of the intimate connection between the African climate and human origins, several experts said.

Frank Brown, dean of earth sciences at the University of Utah, called the discovery "tremendously important." The research was published in the journal Science.

The core samples document dramatic climatic changes in East and West Africa starting about 2.8 million years ago, when the ancient human family tree apparently split into two branches. The core samples show a second equally abrupt change about 1.7 million years ago, at the time that humanity's most immediate direct ancestor first appeared, according to fossil records. …

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