David Barash in Nautilus:
Sperm don’t get much respect. They’re little more than a bare-bones package of DNA outfitted with a lashing tail. And they’re produced in such vast numbers that no single pollywog counts for very much. We all know about their co-starring role in reproduction. But as a 2023 Nature paper underscores, sperm represent some of the most extraordinary and counterintuitive processes of evolution—which got us all here in the first place. So maybe it’s time we get to know sperm better.
To begin with, spermatozoa not only embody the reproductive prospects of males who make them, they have remarkable agency in themselves. Evolutionary biologists have long known that among many species, males compete with other males, the ultimate fitness payoff being that winners will get to project their genes (via their sperm) to the next generation. But competition is also being waged inside male bodies. Sperm battle to fertilize a female’s egg, but they continue to battle even after copulation, perhaps for their own evolutionary payoff.
More here.