Monday, April 23, 2007

Mass Extinction Cyclicity...Again


The rise and fall of species on Earth might be driven in part by the undulating motions of our solar system as it travels through the disk of the Milky Way, scientists say.

Two years ago, scientists at the University of California, Berkeley found the marine fossil record shows that biodiversity—the number of different species alive on the planet—increases and decreases on a 62-million-year cycle. At least two of the Earth’s great mass extinctions—the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago—correspond with peaks of this cycle, which can’t be explained by evolutionary theory.

Now, a team of researchers at the University of Kansas (KU) have come up with an out-of-this-world explanation. Their idea hinges upon the fact that, appearances aside, stars are not fixed in space. They move around, sometimes rushing headlong through galaxies, or approaching close enough to one another for brief cosmic trysts.

In particular, our Sun moves toward and away from the Milky Way’s center, and also up and down through the galactic plane. One complete up-and-down cycle takes 64 million years— suspiciously similar to Earth’s biodiversity cycle.


...with an extraterrestrial cause no less!

Didn't we do this already with Raup and the Nemesis Affair?

This stuff is really susceptible to statistical artifacts, folks, since the fossil record is known to be very biased: it favours animals that live in places that are easily fossilizable and it all depends on whether or not the strata are easily accessed to be studied.

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