Scientists have found that on average mammal species enjoy only 2.5 million years of life before being wiped out because of the Earth's "wobble."
They say when the tilt and orbit reach key points it can spark dramatic global cooling - and the last time this happened was 2.6 million years ago.
This suggests we are overdue a wave of extinction.
However, before you panic, scientists say our planet has changed beyond all recognition in the last 3 million years.
The new research published in the journal Nature (must keep) however sheds new light on just why individual mammal species seem to come and go with mysterious regularity.
The study, conducted by researchers at Utrecht University in the Netherlands, involved looking at 22 million years of data on rodent species to see which ones appeared and died out at key points.
They then studied the pattern of the Earth's wobble, which is caused by two factors, our orbit around the sun and the tilt of the planet.
Both of these can be slightly altered by the gravitational pull of other planets, in the case of the tilt it can adjust by as much as two degrees, and the orbit can vary from a circle to an ellipse.
Lead researcher Dr Jan van Dam said when the tilt reaches a certain point and the orbit is almost a perfect circle it can trigger ice sheet expansion.
This could then lead to colder summers, changes in humidity and significant climate cooling.
He found a clear pattern between the Earth's wobble and mammal species dying out.
There were two distinct cycles of species turnover, one with peaks every 2. 5 million years and the other every million years.
Dr van Dam said the last peak was 2. 6 million years ago.
Thursday, October 12, 2006
WOBBLE ON THIS
The Daily Mail makes Thursday ever so much gloomier with this little ray of sunshine. Doomsayers, rejoice:
Van Dam him.