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Maybe It Wasn't The Meteor, After All
An anonymous reader writes "In one new argument, David Penny of Massey University in New Zealand and Matt Phillips from the University of Oxford contend the fossil record and the evolution of animals through modern times suggest the demise of dinosaurs began several million years before the catastrophic asteroid collision.
'"We agree completely with the geophysicists that an extraterrestrial impact marks the end of the Cretaceous," said Penny, in a statement reported in newspapers and on the Internet this week. "But after 25 years [scientists] have still not provided a single piece of evidence that this was the primary reason for the decline of the dinosaurs and pterosaurs."'"
People much smarter than you already determined that the K-T boundary is uniformly deposited (in terms of time) across the earth, no matter which craton you examine, and it occurs at the same point in time as a significant biomass die-off.
This indicates that a extreme amount of dust and ash must've been airborne for many years, blocking much of the sunlight that would normally enable plant life to flourish. While it is entirely feasible that dinosaurs were in decline prior to this time, the event that killed them is the same one that ultimately created the K-T.
Yeah, right.
Well, it was a lot younger in terms of the raw number of years, but still 99% of it's present age. It's been around for a long time.
I should preface this by admitting that I'm not a palentologist or a geologist, but this sounds like a sketchy argument. It is (as the article points out in the middle) difficult to pin down the date of an extinction from the fossil record. Since only a small fraction of the dead organisms are preserved, you will generally see the last fossil of a given species some time before the actuall extinction event, even if the extinction is basically instantaneous. (i.e. -- a steady population to the moment of extinction, then zero population.) We had a colloquium speaker here in my (Astronomy) department a couple of years ago who explained how this works in pretty convincing detail. So you'll always see what looks like a decline in the biodiversity before an extinction event. Exactly how to deconvolve the effects of the spotty fossilization and the actual event itself is a bit tricky. So I approach the claims for the gradual decline with a lot of caution.
Which isn't to say that it's impossible. But given the trickiness of the data analysis and the odd coincidence of the asteroid impact just then, I'm skeptical.