We know that the upshot of sex between a man and a woman is more than 50 million sperm racing to reach one egg, though exactly how sperm swim through a woman’s body and how just one survives the journey to fertilize an egg is full of mystery.

However, a researcher at Kyoto University says he has found a major clue: a simple mathematical formula to explain the rhythmical swim of a sperm.

Kenta Ishimoto, an assistant professor of applied mathematics at the university, together with researchers at the universities of York, Birmingham and Oxford, has found that the sperm's tail creates a "four-beat" rhythm that pushes the sperm forward but also pulls the head backward and sideways.