They studied rodent fossil records in central Spain dating back 22 million years and found that the rise and fall of mammal species was linked to changes in the Earth's behavior which caused cooling periods.The scientists say the cycles are associated with lower temperatures, changes in precipitation habitats, vegetation and food availability. Learn more at Reuters.
"Extinctions in rodent species occur in pulses which are spaced by intervals controlled by astronomical variations and their effects on climate change," Dr Jan van Dam, of the Utrecht University in the Netherlands, said.
The researchers found two cycles corresponding to the disappearance of rodent species. One lasts 2.4 million years and is linked to variations in the Earth's orbit. The other is a 1.2 million year cycle relating to shifts in the tilt on the Earth on its axis.
Earth wobbles cause mammal extinctions?
Posted on Sunday, Oct 15 2006 @ 09:57 CEST by Thomas De Maesschalck
Dutch scientists claim wobbles in the Earth's orbit and tilt are associated with extinctions of rodent and mammalian species.