Researchers at New York Medical College may have discovered a key genetic reason for the extinction of the dinosaurs. It turns out that modern birds (which are directly descended from dinos) lack a gene for manufacturing adipose tissue--the "brown fat" that bears use to hibernate during the winter, and that helps keep baby mammals (including humans) warm.

How would this have affected your average dinosaur? Well, during the Cretaceous period, the climate was comfortably warm and muggy. But after the K/T asteroid slammed into earth 65 million years ago, the resulting global cooling would have made the average T. Rex keenly miss his heat-generating adipose tissue--and dinosaurs would have died out faster than mammals.