Duck penises show arms race between sexes
‘What they found surprised them — corkscrew-shaped oviducts, with plenty of potential dead-ends.
“Interestingly, the male phallus is also a spiral, but it twists in the opposite, counterclockwise, direction,” said Yale ornithologist Richard Prum in a statement.
“So, the twists in the oviduct appear designed to exclude the opposing twists of the male phallus. It’s an exquisite anti-lock-and-key system.”
Brennan believes females evolved convoluted oviducts to foil the male rapists.
“You can envision an evolutionary scenario that, as the male phallus increases in size, the female creates more barriers. You get this evolutionary arms race,” Brennan said.’
