In most mammal species, fathers have nothing to do with their offspring after mating. Caring duties fall to the mother and, in some animals like elephants, her female relatives.
Humans, mostly, are exceptional. Most dads remain involved in the lives of their offspring for many years, caring for them, teaching them and putting food on the table. But compared with mothers, the investments dads make vary quite dramatically among societies and among individual men.
Given this variation, the benefits of paternal care are not nearly as well understood as we might wish. Especially for sons.
Daughters in the industrialised world whose fathers are absent do worse in school, start menstruating earlier and become mothers at younger ages than similar girls from two-parent families.
Evolutionary biology explains these as effects of a shortened life expectancy. Instead of taking their time to mature, learn and wait for the right mate and conditions to become mothers, they get started earlier because the future doesn’t look so bright. The response to important environmental cues (father absence) is an evolved adaptation to the changed conditions in which she is growing up.
The results for boys are far more equivocal. Some studies show that father absence results in earlier puberty and parenthood, others show the opposite and still others show no effect at all.
One possible cause of this confusion is that when a father dies or leaves the family, that is one of a suite of stressful events. For example, families in which the father leaves the household also move houses and town more often than two-parent families. And fathers of impoverished families are more likely to die young. If stress itself has different effects from paternal absence, this may explain the contradictory results of various studies.
I was encouraged to see a recent paper in Biology Letters, in which Paula Sheppard and Rebecca Sear statistically disentangle the effects of stressful early life experiences from the effect of father absence on the development and start of reproduction of nearly 10,000 British men (from a survey of children born in 1958).
About 7.3 percent of boys lost their father before the age of seven, 2.5 percent between 7 and 11 and a further 4.6 percent between 11 and 16. And the age at which the child’s natural father either died or left the household makes a difference to the results.
When a boy’s natural father is absent, he becomes more likely to have a child by the age of 23. This effect was strongest in boys whose father were absent by the time the boy turned seven, 44 percent of whom had sired at least one child of their own by the age of 23 (compared with 37 percent of boys from two-parent families).
But boys who did not reside with their fathers matured (measured as voice breaking) slightly later, with the strongest effect being in boys whose fathers were present until the boys were 11, but absent by the age of 16.
So the picture seems to be genuinely complex, rather than some of the previous studies confounding childhood stress with father absence. Teenage boys seem, in this respect, to be more complex than their sisters.
One of the possible reasons boys’ puberty and maturation gets so complex is that men can play different strategies. For some boys, the best evolutionary outcome can come from investing heavily in his family, possibly after establishing himself economically and attracting a fecund wife who will be a good parental collaborator. For others, it remains possible to mature as fast as possible and then mate with and possibly desert one or more women.
I’m not really suggesting that men fall into either one or the other of these categories, but rather that the balance of effort men invest in long-term family-man strategies and short-term mate-and-desert strategies can shift. Boys whose fathers stick around my have both their fathers’ genetic disposition to be more paternal and the opportunity to grown and educate themselves for the longer term strategy.
Boys whose father leave might inherit a proclivity to do the same, and they may be forced by circumstances to grow up faster than they otherwise would have done.
Comment here or Tweet @Brooks_Rob This is a complex and potentially explosive suite of ideas, but one I think an evolutionary perspective can help us understand. But the discussion is more likely to be fruitful if we avoid the antiquated habits of batting exclusively for nature or nurture. The stakes are too high to fall back into that trap.