How Sex Works is a new book by award-winning neurogeneticist and evolutionary biologist Dr Sharon Moalem, which challenges some common perceptions about how our bodies function.

We asked Dr Moalem for his three favourite revelations:

Size does matter. There are ethnic differences in average penis size but it’s not what you think.

The greatest differences between ethnic groups are in the unaroused state.

The reason for this difference is possibly due to evolution. If your ancestors were originally from a part of the world with a cold and unforgiving climate, then being large while unaroused would have put them at increased risk of frostbite.

Men aren’t the only ones who can ejaculate during orgasm – women can too. In the past few years, there has been an upsurge of research into the female sexual response and one of the discoveries is that most, if not all, women can probably ejaculate.

The possible evolutionary benefit of this little-known aspect of female sexuality is that female ejaculation actually helps to protect women from urinary tract infections.

While millions of Americans and Europeans are getting Brazilians, there’s a growing demand for pubic hair transplants, which use hair from the back of the scalp, in other parts of the world.

Why? In countries such as Korea and Brazil, pubic hair is considered a sign of fertility.