Australia's egg-laying mammals provide clues to our earliest ancestor

Platypus fossils and DNA suggest all mammals started out as venomous egg-layers

I like the duck-billed platypus
Because it is anomalous.
I like the way it raises its family
Partly birdly, partly mammaly.
-OGDEN NASH

The platypus is famous for being one of the world's strangest animals. When specimens were first shipped back from Australia, it was thought to be a taxidermic hoax. "Of all the Mammalia yet known", wrote George Shaw in 1799, assistant keeper of the natural history department at the British Museum, "it seems the most extraordinary in its conformation; exhibiting the perfect resemblance of the beak of a duck engrafted on the head of a quadruped."