system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some sperms swim faster than others? Is it caused by differences in the DNA they carry, or some nutrient variance between them?
gpt
"Boy sperm" swim a bit faster because they are lighter: the Y chromosome is smaller than the X chromosome.

More significant reasons are going to be deformation and blind luck: doesn't matter how fast it is if it swims the wrong way or the tail is wonky, for example.