Wednesday, December 26, 2012

Environmental Dynamics ~ an essential force in evolution (e! Science News)

Fluctuating environment may have driven human evolution

Published: Wednesday, December 26, 2012 - 09:32 in Earth & Climate

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The researchers examined lake sediments from Olduvai Gorge in northern Tanzania, looking for biomarkers -- fossil molecules -- from ancient trees and grasses.
Credit: Gail Ashley
A series of rapid environmental changes in East Africa roughly 2 million years ago may be responsible for driving human evolution, according to researchers at Penn State and Rutgers University. "The landscape early humans were inhabiting transitioned rapidly back and forth between a closed woodland and an open grassland about five to six times during a period of 200,000 years," said Clayton Magill, graduate student in geosciences at Penn State. "These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years."
According to Katherine Freeman, professor of geosciences, Penn State, the current leading hypothesis suggests that evolutionary changes among humans during the period the team investigated were related to a long, steady environmental change or even one big change in climate.
"There is a view this time in Africa was the 'Great Drying,' when theenvironment slowly dried out over 3 million years," she said. "But our data show that it was not a grand progression towards dry; the environment was highly variable."

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