In Plingy the Elder's Natural History (23-79 AD), he tells a story regarding beavers. He reports that beavers castrated themselves in order to escape hunters who pursued them for their testicles, which could be employed to produce the analgesic medication. This of course isn’t true. Discuss why Darwin would’ve considered it reasonable that lizards must drop their tails, but implausible that beavers must self-castrate even to spare their own lives.