Looking at the animal skin that had been shipped to him in England from Australia, George Shaw, the keeper of the natural history collection at the British Museum at the turn of the 19^th century, was dumbfounded. It was as though someone had taken the webbed feet and bill of a duck and jammed them on to the torso of a fuzzy four-legged mammal. Though he eventually accepted the platypus as authentic, at first he wondered whether someone had stitched various creatures together as a joke.

Two centuries later, the platypus continues to astound scientists. Along with the four species of echidnas, they’re the only mammals that lay eggs. They’re also one of only a few