A woman's eggs choose lucky sperm during last moments of conception, study finds - CNN
Watch a human sperm under a microscope, and it will appear to swim like an eel wiggling its tail through the water. Researchers scanned human sperm samples with a 3D microscope and a high-speed camera—one that could keep up with the speedy swimmers, which can manage 20 to 30 swimming strokes per second. Though in two dimensions sperm appear to lash their tail from side-to-side in symmetric strokes, the reproductive cells actually move in a lop-sided manner , beating their tails to one side only as seen in the video above , the team reports today in Science Advances. This movement should cause the sperm to swim around in circles, but they have found a solution that allows them to propel forward, the team found. Their heads spin in one direction, while the tail rotates around it in the opposite direction in a process known as precession—much like Earth spinning on its axis while orbiting the Sun.