Comment by Retric

There’s a big difference between mostly the same and actually the same. A sperm that doesn’t move is extremely unlikely to fertilize an egg. Thus, 1 is a test for fitness among a tiny percentage of total sperm but still a large number.

Length of survival is dependent on factors largely put side of sperms control, but sperm lifespan does test for massive genetic abnormality.

So yes 99% never get a chance to compete, but meaningful competition still occurs.