Some species eat their own young.
there's a reason for it
I don't know what it is, but there is a reason
plus the only animals that do it (besides a species or two of sharks) are insects
all of which are pretty badly evolved, except the cool ones like ants and those acid shooting beetles
We have wars and abortions and serial killers.
we have wars over land disputes usually, other times it's when someone was an idiot and did something they shouldn't have
abortions are sometimes required in order to save the life of a mother, other times done on teenagers to prevent possible problems with giving birth. besides that, sometimes some people face the fact that they couldn't properly raise a child. in that situation a better choice would be adoption, but what do you expect from someone who can't raise a kid right?
on the matter of serial killers:
there's a reason people who do it are declared mentally insane
I say, that those are perhaps some pretty natural ways of population control.
no, natural ways of population control are predation, natural disasters, and disease