The Cautionary Tale Of The Heike Crab

The Heike is a crab, native to Japan, with the distinguishing feature of what looks to be a samurai face on its back. The legend is that the Heike (Taira) tribe, failing in the battle of Dannoura towards the turn of the 13th Century against the Minamoto clan, committed suicide by retreating to the sea. The crabs embody the souls of these warriors.


Coincidence and urban myth aside, how can a crab's shell encapsulate such a striking resemblance to a face?

The answer is ingenious, and falls to Carl Sagan in the following clip (the answer towards the end):


If you can't be bothered to sit through it (or pick up some Spanish as you go), the reason is because of natural selection: later generations of fishermen kept to a superstitious sentiment of the crabs and would throw any with the strange pattern back to the sea. Thus these few crabs had free reign to populate.

Case solved. Scully would be proud.