https://www.pnas.org/content/102/21/7618 https://www.pnas.org/content/102/21/7618 Thank you for reminding me of my favorite evo bio article of all time. In thi

https://www.pnas.org/content/102/21/7618 https://www.pnas.org/content/102/21/7618 Thank you for reminding me of my favorite evo bio article of all time. In this particular species, females preferentially mate with the largest penis they can find, which applies strong selective pressure to hang dong. Unfortunately they're fish, so it's harder to swim if they're packing heat, making them more likely to get eaten by predators.