We humans are complex creatures when it comes to mate selection. Certain prevailing characteristics may be evaluated differently in different contexts. Money may be more important than physical appearance one day, but the next, intelligence is more important than money but not more important than appearance. It all depends upon the person evaluating and the person being evaluated. However, people tend to also highly evaluate a potential mate’s family tendencies when contemplating a permanent mate. For the purpose of this argument, it must be recognized that modern contraceptives negate the idea that sex automatically equals offspring; thus in this essay, I am evaluating the nesting instinct in the context of long-term relationships, not one-night-stands with accidents or teenagers’ accidental child-producing relationships. And, because divorce is complicated and certainly has greater social underpinnings than anything else, I shall not address it.

A recent study came out that found that women tend to—consciously or subconsciously—put men in two categories: Cads and Dads. Women tend to date the “Cads” but actually marry and settle down with the “Dads”. They find the cads only temporarily appealing—lots of fun, looks, and flattery, but not a lot of stability, especially since the cads tend to find new mates rather quickly. These days they keep their genes in the gene pool by accidental out-of-wedlock children or by failed long-term relationships. On the other hand, the dads are the often less-attractive ones who offer not the whirlwind relationships, but the stability of the long-term loving relationship—the kind within which it is suitable to raise children. The study found that women lowered the physical appearance requirement of their dating days when they choose a permanent mate. This was lowered in favor of a mate who guarantees them a constant environment, genuine love more than lust, and companionship, not just sex.

Women always seem to find attractive—or at least cute—men who like children. Real life alone proves this one. When a man is holding and playing with a baby, every woman in the room thinks it’s adorable. After having children, women brag about how good their husbands—or significant others—are with their children. For the sake of this argument, we’ll define “good with / liking children” as men who are fully capable of playing with children and holding babies and genuinely enjoying it—i.e., smiling and laughing or simply just looking at the child as if they like the interaction. Though it is not a perfect indicator for a man’s fitness to be a father, the man who likes holding the baby is probably a better candidate than the one who backs away. Of course, the definition of “father” as it is being used here is not just being the contributor of sperm but also as an adult who cares for the child.

It has been speculated that two years is the “natural” lifespan of a relationship as determined by evolution. It is apparently the time necessary to conceive, give birth, and know that a child will survive—and that is the point at which males tend to leave the females because they know their offspring will be all right and then can go make more. While all that may be true, how do we justify the relationships that last more than that? It just does not make sense. That theory must therefore be thrown out—at least in the modern sense. As society developed, monogamy and joint child-rearing may have developed together. Two years may be enough to ensure a child’s survival for a little while, but when one really looks at it, humans tend to stay with a child from birth until marriage—or at least until they can survive on their own. And if there are multiple children, the families exist until the youngest child is grown—and even beyond that—if a couple has raised children together over a period of decades, they do not just go off and find another mate because they are done with their last mate.

The female desire to find a mate with nesting tendencies is incredibly advantageous to the species. Raising children is an exhausting process—it is far easier if there are two parents to share the time and energy. Of course, it also allows one parent to support the family while the other raises the children. It also provides for double protection of the offspring from predators. At least in humans in our social context, it has been shown that children with two parents tend to be more stable individuals than those with only one parent; also, having both parents allows boys to have a stable male role model and girls to have that female role model. The long-term investments of two parents has been shown to be beneficial to the mental health of a child, and to his pocketbook, too, considering the cost of therapy after a child escapes a dysfunctional family. In addition, when a child has a stable environment growing up, it teaches that child about how they, in turn, should raise their children.

The development of monogamy probably occurred around a growing social structure. Perhaps as our ancient ancestors were wandering around Africa, they began to organize their little tribes into pairs for the purpose of raising families. As the peoples began to stop randomly wandering, it would make sense that the pairings would grow more and more monogamous and exclusive—into the predecessor of what we like to call marriage today. Although there are cultures around the world which are polygamous, as well as some royalty, most peoples tend to support monogamy. We know that until about the time of Colonialism, the African tribes had polygamy only in the instances when a man could afford to care for multiple wives. However, for the most part, major cultures have been monogamous for centuries. The family structure probably developed as a way of ensuring proper care of offspring. The individuals who could not support families or were uninterested in trying were selected out of the population.

Because of the obvious social influence of this, it would be difficult to determine what effects physiological and genetic evolution has to do with it. Nurture obviously has a lot to do with the nesting instinct. Parents raise their children a certain way that determines how they will in turn rear offspring. Society also responds to children’s looks. Males who know they are attractive are more likely to exploit it and become what pop culture calls “players,” regardless of upbringing. However, physical attractiveness does not necessarily follow genetics; perfectly attractive people can have the ugliest children. Also, men who have fathers who cheat are also more likely to cheat. Nature or nurture? It is almost inevitably a nurture issue. But what if, like the gay gene, there is an infidelity or “nesting” gene which influences a man’s—or woman’s, even—ability to be monogamous? This would be one of the hardest studies ever conducted. People do not like to admit to their indiscretions and it would be even harder to get them to talk in-depth about them. And where does one even begin to look for an infidelity gene? Let us say that one day, researchers are able to get enough subjects and data to find the gene, it is probably not the case that parents would abort a child because it might one day be unfaithful to its partner, but partners may be required to take tests to check for fidelity or family tendencies before they get married—a DNA test instead of a syphilis test. It sounds silly, but if it were true, then the only caution I would give is that infidelity is a choice—a person elects to be in certain situations and act certain ways. Fidelity is a question of morals. And the same for being a good parent. They are both behaviors that may be influenced by evolution and genetics, but when it comes down to it, society ingrains morals and norms into its participants, be it by nature or nurture, and people act based upon those. The consequences of such a finding probably would be have little effect upon society. Genetics may be able to indicate a higher chance of being unfaithful, but it cannot tell exactly whether or not the person will be that way. Genetics cannot ultimately tell us how people will act—nurture has too great of an influence. Besides, why spend the money on a DNA test if one can just ask an ex-girlfriend or ex-boyfriend?