It's a nice article, but the realistic view is that pair-bonding in animals (and, yes, humans are animals) evolved to provide resources and stability to childre

It's a nice article, but the realistic view is that pair-bonding in animals (and, yes, humans are animals) evolved to provide resources and stability to children. Couples are prone to a "seven year itch" which corresponds to the time at which children are able to move away from their mothers and the family unit psychologically. Pair-bonding is reinforced by a common purpose: the child or (as a proxy) some other shared goal. When these disappear, the bond weakens. It's a very natural occurrence. Romantically, we want these things to last for life, but the evolved machinery that we are born with does not provide as much reinforcement as we need to make that happen consistently without some of the problems listed by the article.