Guys -- your sperm is smarter than you think. Depending on your own maths skills, it may even be smarter than you, with new research suggesting that sperm can do calculus. My own grasp on calculus has dimmed a lot since my secondary education -- I seem to recall arguing with one of my maths teachers that I wouldn't use it all that much, and in one broad sense I haven't -- but that doesn't mean my body hasn't been busy with its own calculus.
It was already known that sperm reacts to the concentration level of calcium released by eggs, but it was presumed that it was purely the concentration level that determined the little wriggler's swimming speeds and direction. It turns out that it's not the concentration level itself, but the change in concentration that makes this change, and that's something the sperm has to calculate. The German researchers are quoted in the official release (an unfortunate choice of words, but there you go):
"Using an ingenious stroboscopic laser illumination – similar to that used in discotheques – the project leader Luis Alvarez was able to trace the movement of sperm in detail, and simultaneously measure the changes in the calcium concentration. The result was astonishing: the sperm tail only reacted to the time derivative of the calcium concentration and the absolute concentration was of little relevance. To put it simply: sperm can perform calculus! Exactly how they do this is unclear. The caesar scientists suspect that sperm detect calcium ions with the help of two proteins. Calcium binds to one protein fast and to the other slow. By comparing the amount of calcium bound on both proteins can compute a “chemical derivative”, so to speak."