Have you ever looked at a penis (either your own, or someone else’s) and wondered: why is it shaped like that?

The tube shape is pretty obvious. It fits inside another person nice and neatly, and it’s a good shape for getting sperm up to the top of a vagina (it’s also a good shape for lots of other things, but we’re talking on a biological basis here rather than sexyfuntimes).

So, you’ve got a tube shape, and that makes lots of sense. But what about the bit at the top? For anyone who isn’t familiar with penises, the top bit is technically called the glans and more commonly referred to as a ‘bellend’ and it’s sort of fluted. A bit like a mushroom. Which is a strange bit of design.



But actually, there’s an evolutionary reason for the shape. According to research from a team of scientists, led by one Professor Gordon Gallup (yes, really) the shape of the penis is there to allow it to scoop out other men’s semen from a woman’s vagina during sex.


So back in the olden days when women were encouraged to enjoy the occasional orgy for the sake of reproduction, when she had sex with a whole load of men, there would be a surplus of semen inside her. In order for a man to stand the best chance of being the one who fertilised her with his sperm, his penis evolved to drag other semen out as he withdrew, in theory making it more likely that he would be the baby daddy.

In order to explore this theory, the New Scientist did an experiment. They put a mock-up penis with a sizable coronal ridge (aka big bell end) into a fake vagina, and measured how much of a cornstarch mixture it could pull out, compared to a fake penis with no bell end or a smaller bell end. They found that the penis with the massive ridge was able to remove 90% of the cornstarch mixture with just one thrust.

These days we’re a bit less into the whole free love, not sure who the father is thing (though that is sort of the plot of Mamma Mia Here We Go Again) so that function possibly gets less airtime. But it’s nice to know exactly what your body is capable of.

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