From: Ad 

OK in the long run but consider...

http://news.bbc.co.uk/1/hi/sci/tech/6503045.stm

"However, the supertree shows that the placental mammals had already
split into these sub-groups by 93 million years ago, long before the space
impact and at a time when dinosaurs still ruled the planet.

After the origin of these sub-groups - or orders - the rate of mammal
evolution fell and remained low again until the Eocene Epoch, 55 million
years ago.

The start of the Eocene was marked by rapid global warming and an explosion
in the diversity of mammal lineages. "


Adam

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