Why Do Humans Pair-Bond Anyway?

Why Do Humans Pair-Bond Anyway?

Silvery marmoset & young

I've been contemplating pair bonding. In a variety of species, there is a distinct advantage to the parents, for at least part of the process, to be in pairs. Examples range far and wide through the animal kingdom. There are wolves that take turns hunting and regurgitating food for their pups, certain raptors who alternate sitting on their nest, or marmoset monkeys who prove to be such devoted dads that even other ovulating females won't impact their parenting skills and can't lure them away for a little monkey business. Instead, they stay to attend their young, not even showing a tell-tale increase in testosterone levels indicating arousal. We've all heard about the trumpeter swans mated for life, though bald eagles, albatrosses & turtle doves (practically symbolic of couples - engendering the term being "lovey-dovey!") engage in the same behavior, and even French angelfish will form a bond that means you won't find them swimming solo. Several rodent species such as the prairie vole and the deer mouse will groom and care for each other and their young pups.

While some animals mate for life, some will mate for only a season, and others spend only a short period of time as a couple, but both may take responsibility for dual parenting.

Still, while there are some species that both care for their young, yet others developed entirely different circumstances - such as the male seahorses who will carry the eggs of their young, the male Emperor penguin who stands in the cold, dark, Antarctic winter keeping the egg warm while the females make the long trek to the sea to feed the newly-hatched chicks. In this case, the heftiest males are the most desirable partners, as the skinnier males will be unable to maintain the long vigil until the females return.

And there's the unusual insect known as the giant waterbug who has the couple's eggs glued onto his back by the female, as do several varieties of frogs that keep their froglets close carrying them either in their mouths, or transporting them about piggy-back (or should we say froggy-back!)

Siamese Fighting fish swallow up the eggs and deposit into their nests, even guarding their young afterwards, and a species of carnivorous river fish, the Stickleback, find themselves in a predicament as their favorite delicacy is eating other Sticklebacks' eggs. Therefore, the primary duty of the males after building their nests (sealing them together with kidney secretions, of all things!) is to defend their own eggs from the hungry mouths of others and after the young hatch he will gather them in his mouth and spit them back into the nest for safekeeping. (Talk about protective parenting!)

Emus, Spotted Sandpipers & Rheas all get hi-fives (hi-feathers?) for stay-at-home daddy skills, as after laying eggs in the nests, the females will wander off to mate with another male, leaving pops to be a single dad and raise the chicks solo. There are even catfish fathers that will keep their eggs in their mouths, abstaining from eating until his young are born and able to swim out of his mouth.

Working in pairs, or even alternating the responsibilities of nurturing the next generations of offspring, seems to be biologically advantageous. After all, with both parents caring for the young, the responsibility is lessened, the opportunity for foraging, the passing on of skills from hunting to hiding can be learned, and the likelihood of a large majority of the young surviving would seem to be increased. Indeed, for some creatures, the efforts of both parents is required in order for the young to thrive. But this isn't an absolute rule of parenting and single-parent raising of the young is more prevalent than not.

To point, there is also the relative anonymity of spawning fish, or turtles, who leave their eggs in nests in the sand for the young to make their way entirely on their own. There are many insects, mammals, fish and amphibians will never even see their parents in their lifetimes, but there are obvious exceptions to the rule for each of these critters (as evidenced in the preceding paragraphs.)

So since it's not the absolute rule, then what is the main advantage to pair-bonding anyway?

Of course with human beings it's always nice to have someone else to open a stuck jar lid, to scratch that place that itches between your shoulder blades, and handle their portion of the bills. But why, in a genetically predisposed imperative to spread your DNA far and wide, do we humans place such importance on being in a couple, and in most cases (with few exceptions of polygamy and polyandry), humans across all cultures, races and locations will form pair-bonds. (Herein leaving a wide berth around the complex and moral ramifications of monogamy to another article...)

Pair-bonding, dual parenting, or single-parenting - with so many options in evidence in our world, what precisely is the foundation of our biological, social and emotionally-based imperative to form a pair-bond?

And if the raising and nurturing of young is removed from the equation entirely, then wouldn't the primary factor encouraging this couple-forming behavior be undermined?