leeksfromchichis: mononymous: Oftentimes, natural selection isn't of the fittest, only the most vicious.

Not necessarily. Outcompeting can be viciousness, strategy, or just dumb luck.

There's a spiky weed that grows low and short in America. It evolved back when there were rhinoceros type grazers and outlasted the predators. That's viciousness.  Ants have two stomachs, one to digest and one for sharing.  That's a strategy.  Then the humble hot pepper. The chili was going along ok with its spicy, vicious defense. Then along came a dumb ape that liked the feeling of chemical burns in its mouth.  Instead of being grazed to extinction, like many other species this dumb ape has liked, the pepper got propagated and vastly extended its range even as far as space! You can't compete for that kind of thing. That's just everything coming up Milhouse.

bughunter: The chromosome may contain regions that promote their DNA's spread by killing sperm that carry Y chromosomes. However, Y chromosomes may have evolved counter mechanisms over time

So the sperm are battling it out in my testes?

No wonder my balls ache.