Comment by XorNot
3 days ago
A better way to think about it is just how much surface area of uterus the ovum could actually be in.
It's not that you need millions of sperm or that millions of sperm are competing, its that those sorts of numbers are necessary just to make it probably at least 1 sperm even finds the egg while it's still got energy.
Sperm are actually quite good at finding the egg if they make it to the fallopian tube, they have their own chemoreceptors that can detect very small changes in chemical gradients, but only a few hundred make it through the preceding gauntlet.