Study Links Extinction Cycles to Changes in Earth's Orbit and Tilt:
If rodents in Spain are any guide, periodic changes in Earth's orbit may account for the apparent regularity with which new species of mammals emerge and then go extinct, scientists are reporting today.
It so happens, the paleontologists say, that variations in the course Earth travels around the Sun and in the tilt of its axis are associated with episodes of global cooling. Their new research on the fossil record shows that the cyclical pattern of these phenomena corresponds to species turnover in rodents and probably other mammal groups as well.
In a report appearing today in the journal Nature, Dutch and Spanish scientists led by Jan A. van Dam of Utrecht University in the Netherlands say the "astronomical hypothesis for species turnover provides a crucial missing piece in the puzzle of mammal species- and genus-level evolution."
In addition, the researchers write, the hypothesis "offers a plausible explanation for the characteristic duration of more or less 2.5 million years of the mean species life span in mammals."
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I had to google around for some different versions of that story before I could figure out what they were talking about. The study seems to be a finding that, before we went into the current ice epoch, Milankovic cycles were responsible for a detectable pattern in background extinctions. I had to read a bout four different reports on the same announcement befor someone described the cycles clearly enough to tell that they meant the Milankovic cycles and not some previously unknown astronomical cycle. I don't think I ever found an article that actually mentioned Milankovic. Poor Milutin, he's still getting denied the respect he deserves.
Milankovic, always second behind Tesla!
If anyone can provide a link to the original paper, it would be an interesting read. There's a big difference between finding oscillatory patterns in speciation and blaming extinctions on "ice ages", so there may be something to this, but it's a very tricky proof. Milankovitch cycles overlap, for one thing, so seperating patterns from random walk would be difficult, especially over long stretches of time which include the impacts of tectonic events.