A new study by University of Arizona researchers bolsters the case that fossilized footprints in White Sands, New Mexico, are ...

Iridium is relatively rare in Earth's crust but is more abundant in stony meteorites, which led the Alvarezs to conclude that the mass extinction was caused by an extraterrestrial object.

The notion of bringing vanished species back to life—some call it de-extinction—has hovered at the boundary between reality and science fiction for more than two decades, ever since novelist ...