I have just discovered another (apparent) myth, and a a very curious animal, unrelated except that it’s also about evolution, and it allows me to show some good photos. It's about the heikegani crab, which has lumps on its shell which allegedly look like Samurai. The idea is that the ones that look like Samurai are thrown back into the sea by the fishermen, and so they had a reproductive advantage and now they all look like Samurai. There are a number of problems with this.
The first is that they don’t look like Samurai. If you squint a bit they look like fat Orientals, and I suppose you can see a helmet, which might qualify them as warriors, but from there to Heike, who were a specific clan of Samurai, is quite a leap. It’s not so strange that they would have been associated with a particular group in society, but the idea that those that looked a bit more like Heike than the others would not have been eaten is very strange.
Then there is the fact that, according to Wikipedia (this is all from WP in fact, as until yesterday I’d never heard of Heike or heikegani) they aren’t used as food at all, so they would only be fished by accident. But the evolutionary pressure argument is surely invalid. At any time there must be many millions of these things in the waters around Japan. Only the tiniest fraction of them would ever be caught, and so theoretically subjected to the artificial evolutionary pressure of respectful fishermen. Even over the dozens or perhaps hundreds of generations for which they have been caught (or not, see above), this would have a negligible effect on the shape of their shells.
But it’s a good story, and a curious animal.