"What is it within human beings that makes us cling to relationships beyond the point of comfort?" Is there some little pump in the brain that sends out a chemical that tells us to fear the end or lack of a pair-bond?
nah. its totally "cultural". Its the rules with which we were raised. other cultures have different rules. (polygamy, etc). Our rules were also setup in a time where people didn't live very long as mature adults, so "the long haul" was way shorter than it is today. But the rules did serve their purpose of limiting the spread of disease, the proliferation of destitute women and children, inheritance/property rights, etc...we have other ways of dealing with all of those things, today, but we still seem to cling to the traditions.
