How The Mind Works

Parenting behaviors are tied to the genetic link to children, and one obvious question comes from what happens with stepparents or situations in which the identity of the father is less certain. In these cases, problems are more common. In some cultures, mothers who re-marry are expected to place the children from their first marriage with other relatives. The new father wants a household of children only related to him. Even in cultures with less drastic expectations, Pinker argues that stepparents don’t have the same connection to children who aren’t theirs biologically. Even if they grow to love their stepchildren or at least care for them, they are not biologically wired to feel as connected to their stepchildren or to want their stepchildren’s genes to spread the way they want their own genes to spread.

A mother’s first decision when she has a child is whether to keep it. The decision is legitimate as raising a child requires a lot of resources and sacrifice. If the child is sick or may not survive for other reasons, it is not worth sacrificing the mother’s health and considerable resources for the child. Infants are designed to sway the equation in their favor. They look cute and promote the release of oxytocin, both of which increase bonding. Human children mature over a long time, and they try to maintain the high level of resources they receive from their parents for as long as possible. Siblings complicate the situation. While they share some genetic information, they don’t have all the same genes. When parents bring another child into the family, that child diverts resources but also may make it more likely that the shared genes are spread.

Children compete with their parents as well. Parents couldn’t give literally everything to their children or they would have nothing to survive. They are willing to give a lot, but not everything. Additionally, as children reach an age where they can reproduce, parents can both be competitors for mates and have a vested interest in whom the child chooses. Many cultures don’t allow the children to choose, instead making arrangements that are best for the family more broadly. Choosing a child’s mate is important to parents because there is an interest in the child’s mate having competitive genes and bringing additional resources to the family. Once two people have children, their kin also connected to the other family. These family connections mean they become part of a larger kin network for whom they may behave altruistically or at least helpfully. It is important that these new kin associations be capable and contribute to the larger network through material resources, safety, or connections.

When a marriage (or other committed pairing) works out well, children result, and all parties are mostly happy, but marriages do not always work out well. There are a many potential areas from problems, and in many ways sexual reproduction and committed relationships are costly and difficult to justify in terms of survival. Sex itself appears to be an exaggerated and unnecessary affair compared to simply replicating all your genes and spitting out a clone to carry those genes into the future. Scientists contend that sexual reproduction keeps pathogens at bay. Most microbes are designed to figure out how to latch on to a host and feast for life, and direct clones have the same weak points for the microbes to exploit. Once they figure out one person, they’ve figured out all clones as well. Sexual reproduction changes the puzzle microbes must solve and gives the new life a better chance to survive. Many different systems for sexual reproduction have developed among different species, but they are all based on the idea that one sex invests more in growing and raising the offspring and one sex invests less. The sex who invests less will compete for the chance to mate with as many of the opposite sex as possible, and the sex who invests more will be discriminating in which mate they choose. They must invest months to years in raising the resulting offspring, and they want that offspring to be as healthy as possible.

Men and women have logically opposing sexual desires because of their relative investment in offspring. Men can mate with multiple women without the result of the mating (a child) interfering with the ability to have more mates. Women must choose each mate carefully as they are committing to a long time with the child. It also benefits men to have different partners to ensure their genes spread as widely as possible, especially in case a child does not survive. It can benefit women to have different partners to a point for the same reasons, but it benefits her more to have a partner who will help raise the child. Having two parents providing resources to the child reduces the intense burden on the mother and improves the child’s chance of survival.

It benefits men to have multiple committed partners as well, such as in polygynous relationships—in which one male lives and mates with multiple females, but each female only mates with one male—instead of just multiple partners. Even though women are more committed to the results of each union, they can have sex with multiple partners in a short period, and the identity of the child’s father would be uncertain as it could be any of the partners. Instead, to ensure they have passed on their genes, men would like to have an exclusive commitment from as many women as possible. Polygynous societies demonstrate that wealthy and powerful men can often keep many wives, whereas poor or weak men end up with few or none. It may seem that women benefit from monogamous societies, but polygynous systems have benefits. More women can benefit from a wealthy and strong man’s genes and resources instead of settling for less ideal men because the wealthier men are already taken.

Sexual jealousy arises most often when women are unfaithful to their husbands, but men’s infidelity can evoke jealousy in women. If a woman sleeps with another man, her husband may be fooled into raising the other man’s child. If a man sleeps with another woman, the child born is the other woman’s problem. The only threat is that the man may divert resources to that new child. Therefore, women tend to be jealous about emotional relationships between their man and other women, and men tend to be jealous of sexual relationships. Women are also more likely to assess the likelihood of the infidelity affecting their future and their children’s futures before becoming jealous. In modern societies, things like pre-nuptial agreements and alimony mean that a married man can’t as easily abandon his children born in wedlock. His extramarital relationships may be more threatening in societies without these devices, and we’d expect to see commensurate increases in jealousy if so. Men’s expression of jealousy tends to be swift and often violent, with violence for a woman’s infidelity accepted in many cultures either legally or through less harsh punishment of the man.