The Worst of Times: K-T Still Mysterious

October 19, 2007

There's a very simple rule about evolution that's often forgotten or perhaps ignored because it's so darned depressing: For anything to evolve, a whole lot of species have to go extinct. In the school of evolutionary hard knocks, extinction is a failing grade. You can't  move onto the next grade -- you're out, fossil fodder, you're (pre-)history dude. Adapt or die. Those are the only choices. Nowhere is  this cheery bottleneck of life more glaring than in the mass extinction events that pepper Earth's history. These are, to carry the school analogy to an extreme, the SAT's of evolution. The most famous of these is the Cretaceous-Tertiary boundary, 65 million years ago. It was the death-fest which ended the reign of dinosaurs, of course. For almost 30 years now folks have been pretty content with the idea that a meteor impact caused that die off. But did it? I was reluctant to accept the meteor idea back in the 80s. Seemed a little too sexy and there was a lot of political noise at the time about "nuclear winters", which seemed to piggy back on, and then reinforce the meteor impact mass extinction idea. So it has been with some interest that I've followed the work of Princeton's Gerta Keller and others who believe they have evidence of the Chicxulub meteor striking too early. They say something else did the global murdering. The leading alternative, to date, is the Deccan Traps of India. These are gigantic flood basalts which erupted and flowed across India at the same time dinos died out. The evidence for the Deccan Traps role in the K-T mass extinction is mounting. Will Chicxulub be dethroned? Probably not this year. But stay tuned for the latest in this debate which will likely raise voices and eyebrows at the Geological Society of America meeting, which starts Oct. 28.