Patty Brennan studies the evolution of male and female genitalia in ducks, some of which are extremely long (or deep) and of a complex shape. Using artificial vaginas and high-speed films (highlighted in this Animalogix video), she discovered what happens when drakes try to mate with (un)willing females.

Even species that are so closely related that they are near-identical on the outside, often differ clearly in the way their genitals are shaped. This is why evolutionary biologists believe that genitals are among the fastest-evolving organs in the animal kingdom. In this blog post, you can read about direct evidence, obtained from lizards, that genitals' evolution is indeed measurably faster.

Although we are used to thinking about genitals and sex in the context of males and females, many animals, such as land snails, are males and female at the same time: they are "hermaphrodites". This means that the sexual arms race works in two directions at the same time. In some snails, the arms race is almost literally true: they use "love darts" to stab each other during mating. The aim is to inject hormone-like chemicals into the partner that trick its genitalia to absorb more sperm than they might otherwise have done.

Even if you're familiar with the bizarre world of genital evolution, you are most likely to think that the weirdest bits (chemical warfare, traumatic insemination, multiple sperm storage organs...) are reserved for obscure creepy-crawlies. But in this op-ed for the Huffington Post, educator Menno Schilthuizen shows that all these things happen in humans, too.

Find out more about educator Menno Schilthuizen and his books via www.schilthuizen.com.

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