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mammal evolution

Hi all. This isn't really related to dinosaurs, but I thought I'd try posting
it here. And yes, I do have better things to do on Christmas than post, but I
had to drop in to work anyway because I left all my Christmas cards here, and
I've been meaning to post this for a while now, so here goes.

Since I've had pet ferrets, I've occasionally wondered how far back they'd
have a common ancestor with humans. Also, since *so* many people seem to
think ferrets are rodents or are closely related (despite being carnivores),
I've wanted to find out how far removed they actually are from rodents. Not
that I have anything against rodents, but if someone called a dog or a cat a
rodent, I'd feel inclined to correct them.

I consulted the book 'The Rise of the Mammals', by Michael J. Benton. In
it there's a diagram of mammal evolution which indicates that the paths
leading to rodentia and carnivora diverged roughly 85 million years ago,
whereas those leading to primates and carnivores diverged only 70 million
years ago or so. I thus felt ready to tell all the 'rat-sayers' out there
that *they* are as closely related to rodents as ferrets are.

I was looking through another book though, 'The MacMillan Illustrated
Encyclopedia of Dinosaurs and Prehistoric Animals', and a diagram there
of mammal evolution indicates that the line leading to primates branched
off in the early Cretaceous, maybe 130 million years ago.

So which is right? Or is the history of mammal evolution still that iffy?
I thought I had read of a genetic test that allows you to determine how long
ago two life forms had a common ancestor. Wouldn't it be simple just to run
comparative tests on members of all the existing orders of mammals, in order
to get a more accurate picture?

One more question, 'The Rise of the Mammals' mentions a now extinct group
of mammals I had not previously heard of, the multituberculates. The book
doesn't go into great detail about them, though it mentions they probably
had pouches like marsupials. What are some of the unique characteristics of
this group that separates them from marsupials?

Anyway, time to get to the annual Christmas family gathering. Merry Christmas!

John Rosloot
Regina, Saskatchewan, Canada