Day By Day

Tuesday, April 28, 2009

Death of the Dinosaur Killer

In a recent post paleoanthropologist John Hawks warned against uncritically accepting "umbrella hypotheses" -- those elegant contrivances that would account for a wide range of phenomena by reference to a single, simple explanatory mechanism. He notes that paleoanthropology has historically been susceptible to such monocausal explanations. Examples would include the "savannah thesis" the "killer ape" thesis, the "aquatic ape" thesis, and many more.

Read his article here.

Such explanations are seductive because they are elegant and easy to comprehend and they form the basis for numerous popularized science and history texts and innumerable journalistic accounts. But the world is seldom so simple as these hypotheses suggest and despite their popularity they usually lack staying power because contrary evidence rapidly accumulates to undermine them.

One such elegant hypothesis has been the asteroid impact theory that was held to explain a number of geological features as well as discontinuities in the evolutionary record. Most provocatively, an asteroid impact was supposed to account for the extinction of the dinosaurs.

Well, new research seems to suggest otherwise. Bloomberg reports:
The demise of the dinosaurs probably occurred 300,000 years after a giant meteor struck what is now Mexico, scientists said, casting doubt on a popular theory that the impact triggered a mass extinction.

The Chicxulub crater, which is about 180 kilometers (112 miles) across, was formed on the Yucatan peninsula when an extra-terrestrial object struck Earth 65 million years ago. Since its discovery in 1978, the crater has been cited as evidence that the impact’s aftermath led to the extinction of about 65 percent of all species including the dinosaurs.

New clues at other sites in Mexico showed that the extinction must have occurred 300,000 years after the Chicxulub impact and that even larger asteroids may not be the purveyors of doom they’re thought to be, according to a paper published in the Journal of the Geological Society by researchers from Princeton, New Jersey, and Lausanne, Switzerland.

Read the whole thing here.

And another scientific consensus bites the dust.

Oh well, the impact theory had a good run, about a quarter of a century, and it inspired a lot of books and TV shows that made a lot of money for a lot of people and in modern science, that's ultimately the name of the game.