60-Second Science

Ancient Ancestor Of Humans, Dogs, Cats, Llamas, Sloths, Marmots...

The fossil of a small, shrew-like mammal, found in the Gobi desert 10 years ago, is a member of the taxonomic group that gave rise to all modern placental mammals. Steve Mirsky reports.

The little guy lived more than 70 million years ago in what’s now the Gobi desert.  In 1997, his remains were discovered by fossil hunters.  And in a paper published in the new issue of the journal Nature, researchers announced that they think he’s a member of the kind of mammal that is the ancestor of us all.  And I do mean all, all placental mammals, you, me, Fido, Felix, manatees, elephants, every placental mammal now living on earth. 

The tiny ancient shrew-like mammal is called Maelestes gobiensis.  Researchers analyzed over 400 anatomical features of 69 species of living and other fossil mammals, along with the recent discovery.  The genealogical tree they drew puts our common ancestor right about the same time that the dinosaurs began to dwindle, due to a giant impact event some 65 million years ago. 

So the little shrew offers confirming evidence that the disappearance of the dinosaur lines that didn’t go on to become birds was what allowed mammals to evolve into the multiple forms we see today.  And to take advantage of all the opportunities the dinosaurs left behind. 

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