Can they help it?
Monogamy and polygamy are instincts
I think it can even vary between race.
The higher the infant mortality rate in a given region of the world, the most successful of a species will be polygamists. In the desert, the survival of the species depends upon every eligible female to be incubating a baby.
That being said, we are aware of many cultures in arid environments and other hostile climates with high infant mortality rates that holds that a man’s prowess is exemplified by the number of women carrying his baby. Harems and tribes as notable examples specifically.
I’m not sure how far apart the term instinct and impulse are.
It also stands to reason that specimens with lower levels of libido, virility, fecundity would die out. Members of the species with more stamina, and survivability under more adverse conditions would be the successful specimens.
