Dinosaurs' Demise Didn't Trigger Mammals' Rise

Instead, mammals flourished during later period of global warming, study finds

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WEDNESDAY, March 28, 2007 (HealthDay News) -- The extinction of the dinosaurs did not directly result in the rise of modern mammals, according to a study by researchers who spent more than a decade tracing the history of all 4,500 types of mammals through fossil records and molecular analyses.

The study, published Wednesday in the journal Nature, contradicts the widely-held theory that the "mass extinction event" that wiped out the dinosaurs 65 million years ago also set in motion the rapid rise of modern mammals.

While dinosaurs ruled the Earth, there were few mammal species. After the mass extinction event, there was a busy period of mammal diversification and evolution. However, most of those earlier mammal groups have since died out or declined in diversity, the study found.

The ancestors of modern mammals actually began to proliferate during a period of sudden temperature increase on the planet, which occurred about 10 million years after the dinosaurs vanished.

"Our research has shown that for the first 10 or 15 million years after the dinosaurs were wiped out, present day mammals kept a very low profile, while these other types of mammals were running the show. It looks like a later bout of 'global warming' may have kick-started today's diversity -- not the death of dinosaurs," Andy Purvis, a professor in the division of biology at Imperial College London in the United Kingdom, said in a prepared statement.

"This discovery rewrites our understanding of how we came to evolve on this planet, and the study as a whole gives a much clearer picture than ever before as to our place in nature," Purvis said.

More information

The University of California Museum of Paleontology has more about mammals.

SOURCE: Imperial College London, news release, March 28, 2007


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