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Men’s investment in their children is one of the most remarkable features of the human family. Such investment might not seem unusual to readers with engaged fathers, but it is a riddle in terms of the broader evolutionary picture. This is because male is uncommon in mammals, and does not occur at all in our closest living relatives (chimpanzees and bonobos). Here, I’ll outline a few of the factors that likely contributed to the evolution and evolutionary maintenance of men’s parenting and in a later post will discuss the here-and-now (proximate) factors that influence when, with whom, and how much individual men invest in parenting.

From an evolutionary perspective, male parenting first and foremost must provide some non-trivial benefit to offspring, such as reduced mortality risks or enhancement of competitive abilities in adulthood. At the same time, these benefits have to be balanced against the potential costs to males, including his lost opportunities and risk of cuckoldry (i.e., unwittingly investing in the offspring of another male). My focus here is on the benefits of men’s parenting, but I’ll state upfront that cuckoldry or non-paternity is pretty low in humans, probably well under 3% in most populations, although it can be considerably higher in low-income communities. Men’s mating opportunities are curtailed by women’s aversion to casual and their competitiveness with other women, especially rivals over romantic partners. They backbite, lie about, slur the reputation of, and generally try to expel these would-be competitors from the social group, which makes them unattractive to or unavailable to the aggressors’ romantic partner. The result is that men have fewer opportunities for sex than they would prefer and this in turn reduces the costs of investing in children.

Many books have been written about human parenting over the years, but few if any of them have touched upon the core benefit and function of parenting to keep children alive. This core purpose is sometimes hard to fathom, given the low mortality rates among children in developed nations, but this situation is a very recent phenomenon. In a review of child mortality from ancient Greece to modern-day hunter-gatherer societies, Tony Volk and Jeremy Atkinson estimated that as many of half of all children died before reaching . We might then expect that men’s parenting helps to keep children alive in many contexts, but this is actually debated among anthropologists who study modern-day traditional cultures. Sometimes dads help mothers to keep their children alive and healthy, but sometimes it's other family members, especially maternal grandmother, that contribute the most.

Nevertheless, studies of traditional cultures might underestimate the importance of dads, especially during population crashes and periods of high mortality, as almost certainly occurred on a regular basis throughout human evolution and human history. These crashes are driven by the Horsemen of the Apocalypse—famine, plague, and war—and their timing is unpredictable. Men who abandon their children during good times are rolling the dice, hoping the number of one of the Horsemen does not come up before their children reach adulthood. The importance of men’s investment during these high-risk times is well documented in developing nations and in the historical record for industrializing Europe and the United States up until about 100 or so years ago.

The same pattern was evident in China. Song, Campbell, and Lee analyzed 20,000 patrilineages across six generations from China’s Qing dynasty (1644-1911). During this era, higher-status men had a much lower chance of lineage extinction over the next six generations than did their lower-status peers. Extinction risk was independent of the number of children born in each generation (most men were monogamously married), indicating that lineage continuance was not simply due to higher-status men having more children. During this era and during the predecessor Ming dynasty, the Horsemen of the Apocalypse made frequent and unpredictable visits throughout China, and almost certainly resulted in more mortality among lower-status than higher-status families. In other words, men’s investment of resources in their families and children helps to keep the horsemen of the Apocalypse at bay and their lineage viable, but the payoffs to this strategy might not be strongly evident except during times of high population mortality.

Granted, all of this is a bit morbid, so to speak, but it is the reality of human experiences throughout history and human evolution and is important to consider when trying to understand men’s investment in their children. Even in good times, with low mortality risks, men’s investment in and engagement with their children can make an important difference in their lives, including improvement in their overall physical and psychological health. Father’s involvement with their children also appears to contribute to their social competencies and emotional maturity, and helps to keep them on track during adolescence. All of these contributions enhance their children’s long-term social competitiveness. It helps them to move up the social ladder which, in turn, reduces mortality risks during unpredictable population crashes. Although modern technology, science, and medicine keep these crashes at bay, the point is that an evolved to enhance children’s social competitiveness could easily evolve in contexts with frequent and unpredictable crashes.

In any case, let’s consider the modern-day contributions of fathers to children’s long-term life chances. These chances are enhanced if adolescents stay out of trouble and stay in school, and dads help to make this happen. Steele, Sigle-Rushton, and Kravdal’s study of the relation between or paternal death and 200,000 Norwegian children’s years of schooling nicely illustrates my point. Not only is infant and child mortality very low in Norway, government-funded social supports that mitigate financial hardship make it an especially low-risk environment. Despite the low risks and controlling for multiple other factors, loss of father for any reason was associated with about a 10% reduction in the chances of finishing secondary schooling for boys and girls.

In an informative twist on this type of study, ähler and Palmtag assessed the relation between divorce and Swedish children’s educational outcomes for people born in 1892 through 1991, a timeframe with substantial drops in child mortality and increases in government welfare programs. Despite the reduction in risks, father absence was consistently associated with lower educational attainment for girls and boys throughout the century, controlling other factors (e.g., marital conflict, parental ). Lower educational attainment in turn is associated with an increased risk of delinquent behavior and more and in adolescence and lower life-time earnings. These patterns are consistent with fathers’ monitoring of children’s and adolescents’ behavior and peer groups, in addition to their economic contributions to the family.

There are even more subtle aspects of fathers’ engagement with children that help to keep them on track. Paternal involvement in play, especially rough-and-tumble play, is associated with children’s skill at regulating their emotional states and their later social competence. Children with fathers who regularly engage them in physical play are more likely to be socially popular—chosen as preferred playmates by their peers—than are children who do not regularly engage in this type of play. Several longitudinal studies indicate that this form of play is associated with better social and psychological functioning when these children reach adolescence. Rough-and-tumble play might also signal paternal dominance in a non-threatening way to young children, which then enables fathers to more effectively monitor and influence adolescent behavior. This in turn may contribute to the reduced adolescent delinquency and higher educational attainment of adolescents with engaged fathers.

The bottom line is that in really tough times, fathers’ investment in parenting can be the difference between which children make it through and which do not. In less perilous times, fathers’ investment in parenting contributes to children’s emotional and physical health and improves their social competencies. Fathers can also help to keep children and especially adolescents on the track toward a successful adulthood.