Sunday, August 19, 2007

Does temperature affect evolution?

Where does evolution occur in a temperate area or in a hot area?
It turns out that new species originate more frequently in temperate regions than in the tropics. Steamy and wet they may be, but tropical hotspots of biodiversity are not the hottest as far as evolution is concerned. Scientists looked at pairs of "sister" species - pairs that evolved from an immediate common ancestor - and estimated how long ago the sisters diverged from each other.

In hot areas
Near the equator, sister species split on average about 3.4 million years ago, whereas those in temperate regions split roughly 1.7 million years ago. It is true that tropical zones do host a greater species diversity, but that's because fewer species have gone extinct there.

In cold areas
In very high latitudes - above the Arctic Circle - the sister species split even more recently, with none of those reviewed separating more than a million years ago.

Dramatic climatic changes in temperate regions over the past hundreds of thousands of years may have driven evolution harder.

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