Re: why the dinosaurs became extinct

Of course there are possible reasons, besides an asteroid impact, for the extinction of the dinosaurs. "Asteroid impact" is just a drastic version of the explanation which says that dinosaurs died out because of climatic change: the earth got too cold for them.

Flamboyant paleontologist Robert Bakker, on the other hand, doesn't buy climate change as an explanation: dinosaurs lived in all sorts of climates and were mighty robust animals. Instead, he points out that at the end of the Cretaceous, land bridges opened up between Asia and North America, as well as other places. Bakker thinks that subsequent migrations spread diseases to which other animals were not resistant (in the same way that Native American peoples were nearly wiped out by smallpox, to which the European invaders were resistant). However, this fails to explain the disappearance of a multitude of sea-living species.

We will probably never know the real answer, though we do know that there was at least one sizeable impact at about the right time: the Chixalub (sp?) crater in Mexico is over 100 miles across, and has been dated to 65 million years ago. My amateur opinion is climate change, assisted by asteroid impact.

Dan Berger
MadSci Admin