In some animals, including chimps, multiple males will mount a single female. Their sperm competes with each other’s. Chimp sperm is very stick as it forms a sperm plug at the cervix. Chimps also have long, thin dicks to push said plug off, so that his can enter.
Interestingly, it is evolutionarily beneficial for females to be impregnated by older chimps. Which younger males don’t care about ofcourse. They will still bite and mount regardless of what the female wants. Luckily. When she ovulates, her taint swells up. Increasting the distance between the cervix and the opening. Since dick length is determined by age, only the older chimps are succesful in mating.
Humans have relatively not-so-sticky jizz.
Not much more to tell. I suppose it’s worth mentioning that chimps have larger balls, and produce a lot more sperm than humans do. Their swimmers are also stronger and much better at travelling through mucus. This is because humans became serially monogamous, rather than 1 male tops all and leaves his children to figure out how to avoid inscest. Our sperm just isn’t used to competition anymore.
In case anyone is wondering what the relevance is… we are 98% chimp genetically speaking.
Same reason boogers are. And mucilage.
Protein!
You suspend some proteins in some water, and you got glue
Nature’s glue, duh.