No, we don't just mean that we all have some nasty folks in our family tree--We're talking about an actual rat-like mammal that is the common ancestor of all humans. It weighed about half a pound, had a long furry tail and ate insects (something WE may do more of in the future).
This ancestor emerged within 200,000 to 400,000 years after the dinosaurs died off. However, it took millions of years before the first members of this modern mammal appeared in great numbers. A research team used a combination of fossil evidence and genetic data encoded in DNA to determine the ancestor's status.
In the February 8th edition of the New York Times, John Noble Wilford quotes researcher Maureen A. O’Leary as saying, "The findings were not a total surprise, but it's an important discovery because it relies on lots of information from fossils and also molecular data."
Wilford quotes researcher John R. Wible as saying that the new system enables scientists to look "at all aspects of mammalian anatomy, from the skull and skeleton, to the teeth, to internal organs, to muscles and even fur patterns" to determine what the common ancestor possibly looked like.
The new system can assess each mammal on the basis of more than 4,500 possible traits, which is 10 times larger than previous databases. Wilford quotes paleontologist Michael J. Novacek as saying, "At one point, I didn't think we would ever finish."
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