Ducks not only have one of the strangest sex lives in the animal kingdom, they have also been at the center of a true “evolutionary sex war” for millions of years.
In some species, forced copulation is common, and males evolved genitalia that can give them an advantage in achieving fertilization. But females didn’t lag behind: over time, their anatomy also evolved to give them greater control over who would become the father of their offspring.
And the solution seems straight out of a movie: they practically turned their intimate parts into a maze.
Female ducks developed vaginas with spirals that twist in the opposite direction from males’ penises, making it harder for them to advance. But they also created a set of “fake entrances” or dead ends inside their reproductive tract.
Thus, when an unwanted copulation occurs, the male is more likely to end up in a dead end and fail to achieve fertilization. In other words: you may manage to get in, but that doesn’t mean you’ve found the right path.
According to biologist Patricia Brennan, this peculiar evolution makes it possible to study a genuine “evolutionary sex war”: while certain male characteristics evolved to promote fertilization, females developed obstacles that allowed them to retain some reproductive control.
Those innocent little ducks we see swimming in a lake seem more evolved than many women. 🦆