Societal norms

It is mostly to do with biology. Big brains, fat, long gestation and cryptic ovulation. With chimpanzees, like our small-brained early ancestors, the ability to find food is much the same between the sexes and the mother finds almost all the food for herself and her offspring - some food sharing takes place but it is of minor extent, males do not usually feed infants. Female chimpanzees are obvious - hugely swollen pink pudenda -  when they are ovulating and fertile. Copulation is relatively promiscuous (females only reject close male relatives) and male chimpanzees compete for fertilization largely through semen quality and quantity. It is a bit of a 'chicken and egg' situation, but when our ancestors brains grew, they needed more fat in their food - the brain is very lipid-rich. As a result, a diet rich in animal fat (from animal fatty meat, body fat, marrow and brain) was necessary, mostly obtained by hunting. With a long gestation period and long infant dependency following birth, early female humans could not supply all their own and their offspring's food requirements. Obviously, a heavily pregnant, nursing, or encumbered with small offspring, human female could not hunt. Therefore, humans became reliant of pair-bonded couples, where the male hunted and the female raised children and gathered plant-based food nearer the home-site. This gave rise to problems, the male needed to be reasonably certain that the offspring he was supporting with food were his and the female needed to retain the support of her male. Part of the answer was cryptic ovulation, unlike chimpanzee females it is not at all obvious when a human or, presumably, early human female is fertile. This means that more frequent copulation is selected for, which, alongside greater degrees of pleasure for both sexes in copulation, results in strengthened pair-bonding.

Very many bird species form similar pair-bonds for similar reasons, a single bird cannot incubate eggs, or defend hatchlings, and gather food at the same time.

As in some birds, there is some evolutionary pressure to cheat - the male has more offspring and the female produces offspring with more varied genetics. 

It is mostly to do with biology. Big brains, fat, long gestation and cryptic ovulation. With chimpanzees, like our small-brained early ancestors, the ability to find food is much the same between the sexes and the mother finds almost all the food for herself and her offspring - some food sharing takes place but it is of minor extent, males do not usually feed infants. Female chimpanzees are obvious - hugely swollen pink pudenda -  when they are ovulating and fertile. Copulation is relatively promiscuous (females only reject close male relatives) and male chimpanzees compete for fertilization largely through semen quality and quantity. It is a bit of a 'chicken and egg' situation, but when our ancestors brains grew, they needed more fat in their food - the brain is very lipid-rich. As a result, a diet rich in animal fat (from animal fatty meat, body fat, marrow and brain) was necessary, mostly obtained by hunting. With a long gestation period and long infant dependency following birth, early female humans could not supply all their own and their offspring's food requirements. Obviously, a heavily pregnant, nursing, or encumbered with small offspring, human female could not hunt. Therefore, humans became reliant of pair-bonded couples, where the male hunted and the female raised children and gathered plant-based food nearer the home-site. This gave rise to problems, the male needed to be reasonably certain that the offspring he was supporting with food were his and the female needed to retain the support of her male. Part of the answer was cryptic ovulation, unlike chimpanzee females it is not at all obvious when a human or, presumably, early human female is fertile. This means that more frequent copulation is selected for, which, alongside greater degrees of pleasure for both sexes in copulation, results in strengthened pair-bonding.

Very many bird species form similar pair-bonds for similar reasons, a single bird cannot incubate eggs, or defend hatchlings, and gather food at the same time.

As in some birds, there is some evolutionary pressure to cheat - the male has more offspring and the female produces offspring with more varied genetics. 

This very expansive comment leads me to think about my annoyance at humanity for always assuming we are above nature. How we are in some way different because we have conscious thought

I actually feel that we are flawed because of that. Like how we can't seem to do anything without it being of negative consequence to the natural world .why then do NTs assume the expectations held in human society are optimal asnrhey are then?