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The evolution of animal genitalia

Apparently, no organs evolve faster and into more variable shapes than those involved in procreation.

what's the point of having such decorative nether regions?

After all, the function of genitalia seems simple. A penis deposits a bit of sperm and a vagina receives it and delivers it to the egg.

Throughout the animal kingdom, genitalia are very complex things, much more complicated than seems necessary for what they're meant to do. That's because genitalia do more than just deposit and receive sperm.

Many male animals also use the penis as courtship device, like crane flies, beetles and some hoofed mammals, like rams and bulls.

But how can females really choose between males if she can only assess them after mating?

This is where the power of female adaptation comes into play. In fact, insemination is different to conception, and the female genitalia exploit this distinction.

-some vagina contains pockets for separating sperm from different males depending on how appealing they were.

Males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes.

So we see cycles of adaptation in an evolutionary arms race to retain control.

-Black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals

-bed bug males bypass a female's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly.

females have evolved their own countermeasures.

-In some bed bug species, the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them. That allows them to maintain the power to filter out unwanted sperm with their genitalia.

-And duck vaginas are shaped like a clockwise spiral so that when the male inflates his long, counterclockwise coiled penis into her, and she disapproves, all she needs to do is flex her vaginal muscle and the penis just flubs out.

Genitalia differs so much, not just to fascinate us, but because in every species, they're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come.