Right Wing Nut House

Approximately 65 million years ago, (give or take 3 million years) a fairly large meteor (or possibly a smaller comet) hit the earth in the area of the Yucatan penninsula. Most scientists agree that this event was the proximate cause for the extinction of most dinosaurs.

Turns out that this was not an isolated incident in earth’s history.

With surprising and mysterious regularity, life on Earth has flourished and vanished in cycles of mass extinction every 62 million years, say two UC Berkeley scientists who discovered the pattern after a painstaking computer study of fossil records going back for more than 500 million years.

Their findings are certain to generate a renewed burst of speculation among scientists who study the history and evolution of life. Each period of abundant life and each mass extinction has itself covered at least a few million years — and the trend of biodiversity has been rising steadily ever since the last mass extinction, when dinosaurs and millions of other life forms went extinct about 65 million years ago.

There’s nothing really new as far as the theory goes. Scientists have noticed this before. What makes this study so compelling is that it’s so exhaustive.

The Berkeley researchers are physicists, not biologists or geologists or paleontologists, but they have analyzed the most exhaustive compendium of fossil records that exists — data that cover the first and last known appearances of no fewer than 36,380 separate marine genera, including millions of species that once thrived in the world’s seas, later virtually disappeared, and in many cases returned.

But the cycles are so clear that the evidence “simply jumps out of the data,” said James Kirchner, a professor of earth and planetary sciences on the Berkeley campus who was not involved in the research but who has written a commentary on the report that is also appearing in Nature today

The evidence of strange extinction cycles that first drew Rohde’s attention emerged from an elaborate computer database he developed from the largest compendium of fossil data ever created. It was a 560-page list of marine organisms developed 14 years ago by the late J. John Sepkoski Jr., a famed paleobiologist at the University of Chicago who died at the age of 50 nearly five years ago.

For more than 20 years there’s been some fantastic speculation as to what the heck is going on that would cause regular extinctions. For a while, some scientists were enamored of a theory involving a rouge planet dubbed “Nemisis” who every 65 million years swings into the Oort cloud out beyond Pluto where billions of comets slowly orbit the sun. As Nemisis passes through the Oort cloud, thousands of comets are disturbed and start dropping towards the inner solar system and the sun. Inevitably, several will hit the earth causing massive die-offs.

Then there’s this hypothesis from one of the authors of the study:

Muller’s favorite explanation, he said informally, is that the solar system passes through an exceptionally massive arm of our own spiral Milky Way galaxy every 62 million years, and that that increase in galactic gravity might set off a hugely destructive comet shower that would drive cycles of mass extinction on Earth.

Our Milky Way galaxy spins like a massive pinwheel in space so that passing through one of the arms of our own galaxy could be a possibilty.

Alas, not very likely…But wouldn’t you love to be alive and look up to see tens of thousands of stars rather than the measely 2000-3000 you can see with the naked eye today?

What this also does is raise some interesting questions for the SETI folks (Search for Extraterrestial Intelligence). One of the reasons it’s thought that advanced intelligent life is so rare is that earth may be exceptional for its very long, very stable geologic and cosmological eras. And we’ve been lucky so far in that no “planet killer” sized meteors have hit here probably since the moon was formed about 4 billion years ago. That means that the slow processes involved in the evolution of life has had a chance here.

Other planets capable of sustaining life may not be so lucky.