It’s tough to be sperm. Your entire existence centers on one race that you will almost definitely lose. You don’t even get to take a warmup lap. Nevertheless, a glance at your competitors waiting at the starting line might give you some hints about who has an advantage. One factor that helps sperm win races is length—and not only for the reasons you might guess.
Long sperm generally have longer tails. This ought to make them faster and more powerful swimmers, which studies have confirmed.