You're really asking the wrong questions here Joe. Modern social conditions may tempt us to see ourselves as individuals first, last, and always, but the possibility to do so is very modern and not at all a feature of most societies through time.

If you want to realistically assess pair bonding and long vs. short term relationships you first have to assess the kinship and social identity patterns of the groups the pair bonds form within.

When groups have stark divisions between male and female rolls, pair bonding can be far less a feature than when the economics of the group require more shared effort between members of a pair. Sometimes child rearing is a cooperative effort of largely female groups, sometimes it resides within extended family groups, sometimes as in our current era it is primarily attempted by the "nuclear" family unit.

People can do well under all conditions, and the economic/cultural dynamic always defines gender roles and pair bonding...our profound adaptive trick as humans is to construct cultures that deal with our economic/technical realties, be they hunter/gatherer, nomadic pastoralist, settled small scale agriculture, fishing economies, you name it;)