(Comic I made three years ago. Ignore the twitter logo)
34 points
Serious answer: eggs have a protective barrier around them, so sperm actually need to group in bunches to break the barrier, and a single lone sperm is incredibly unlikely to do well on its own. As such the ones that have a higher chance of success are actually the ones that are last and get in after the barrier’s been weakened.
8 points
15 points
There’s also evidence that eggs ‘choose’ the sperm, or at least filter out some sperm based on genetic factors.
15 points
8 points