So how does one sperm manage to best tens of millions of competitors to fertilize the egg? It may have the best rhythm, a new study suggests. Researchers analyzing how sperm cells move have come up with what they call a "simple mathematical formula" to explain what's happening, reports the BBC. They found that the tail creates a rhythm that propels the sperm forward, pulling the head forward and sideways in what may seem like chaotic fashion but is far from it. The "sperm stirs the fluid around in a very coordinated way to achieve locomotion, not too dissimilar to the way in which magnetic fields are formed around magnets," says Dr. Hermes Gadelha in a release from the University of York. The vast majority of the sperm cannot overcome the resulting fluid drag, but a select few are able to move forward.
"It is true when scientists say how miraculous it is that a sperm ever reaches an egg, but the human body has a very sophisticated system of making sure the right cells come together," says Gadelha, whose team's study is published in the journal Physical Review Letters. This phase of the research focused on the movement of one sperm cell—they fed measurements of the tail's beat into a computer—and the next will try to create a model for larger numbers. Figuring out how the sperm move and why some are more successful than others could theoretically improve infertility treatments in the future, say the researchers. (Figuring out how to diminish sperm's ability to "swim" might lead to birth control for men.)