what you're seeing, but maybe not entirely understanding, is the difference between r-type and k-type reproduction strategy.  long story short, competitive animals such as wolves and lions have small litters and invest a lot of time into their progeny. they are trying to produce high quality babies. non competitive animals such as rabbits and mice and rats have huge litters and invest basically nothing into raising them. they make up in quantity, what they lose in quality. now look at the human race and tell me if you see any analogues to this behavior.
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