Now, British scientists claim to have finally solved the puzzle -- sperms have an appalling sense of direction, crashing into walls and each other in the race to reach the egg, the 'Daily Mail' reported.
On an average, a man releases 300 to 500 million sperm during sex with his female partner, but usually only one sperm enters into her egg.
In their study, the scientists from the University of Warwick and University of Birmingham have found that sperms avoid the "middle lane" of the female reproductive tract and instead crawl along the channel walls.
The sperms also struggle to turn sharp corners and crash into the walls and each other in a scene reminiscent of a demolition derby, say the scientists.
Lead scientist Dr Peter Denissenko from Warwick said: "I couldn't resist a laugh the first time I saw sperm cells persistently swerving on tight turns and crashing head-on into the opposite wall."
The successful sperms were those that were best able to negotiate the complex and convoluted channels filled with viscous fluids, the scientists claim. (MORE)