Evolving Premises

NEW YORK (AP) — The big dinosaur extinction of 65 million years ago didn't produce a flurry of new species in the ancestry of modern mammals after all, says a huge study that challenges a long-standing theory. Scientists who constructed a massive evolutionary family tree for mammals found no sign of such a burst of new species at that time among the ancestors of present-day animals. Only mammals with no modern-day descendants showed that effect. "I was flabbergasted," said study co-author Ross MacPhee, curator of vertebrate zoology at the American Museum of Natural History in New York.

At the time of the dinosaur demise, mammals were small, ranging in size between shrews and cats. The long-held view has been that once the dinosaurs were gone, mammals were suddenly free to exploit new food sources and habitats, and as a result they produced a burst of new species. The new study says that happened to some extent, but that the new species led to evolutionary dead ends. In contrast, no such burst was found for the ancestors of modern-day mammals like rodents, cats, horses, elephants and people.

• JJ Commentary: And so it goes with evolutionary theory. New data doesn’t fit? Fine, revise the premises – over and over again. Never mind questioning the original premise.