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Extinction may be linked to Earth's tilt and orbital variations
mongabay.com
October 11, 2006
A new study suggests that variations in Earth's orbit and tilt may be linked to extinctions of mammal species.
Examining the fossilized teeth of rodents over a 22 million year period, researchers lead by Jan van Dam of Utrecht University in the Netherlands found that the disappearance of mammal species -- which survive an average of 2.5 million years before going exinct -- cluster around specific cycles at one million and 2.4 million years. The one million year cycle correponds to wobbles in Earth's orbit, while the 970,000-year cycle is tied to shifts of the Earth on its axis. The cycles are assocation with lower temperatures and changes in precipitation.
Currently Earth is in a period of axial tilt and an elliptical orbit -- which usually correlate to stable mammal biodiversity -- but high concetrations of greenhouse gases make it difficult to predict what's in store for Earth's mammal species.
The study is published in the October 12 issue of the journal Nature.
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