Sex at Dawn

While a substantial amount of female parental investment is biologically unavoidable in our species, evolutionary theorists believe that Homo sapiens is uniquely high in male parental investment (MPI) among primates. They argue that our high level of MPI forms the basis for the supposed universality of marriage. As Wright puts it, “In every human culture in the anthropological record, marriage . is the norm, and the family is the atom of social organization. Fathers everywhere feel love for their children.. This love leads fathers to help feed and defend their children, and teach them useful things.”¹²

Biologist Tim Birkhead agrees, writing, “The issue of paternity is at the core of much of men’s behaviour—and for good evolutionary reasons. In our primeval past, men who invested in children which were not their own would, on average, have left fewer descendents than those who reared only their own genetic offspring. As a consequence men were, and continue to be, preoccupied with paternity..”¹³

For now, we’ll briefly note a few of the questionable assumptions underlying this argument:

• Every culture is organized around marriage and the nuclear family.

• Human fathers that provided for only their own children would have left far more descendants than those less selective in their material generosity.

• Note how this presumes a discrete genetic basis for something as amorphous as “preoccupation with paternity.”

• In the ancestral environment, a man could know which children were biologically his, which presumes that:

• he understands that one sex act can lead to a child, and

• he has 100 percent certainty of his partner’s fidelity.

• A hunter could refuse to share his catch with other hungry people living in the close-knit band of foragers (including nieces, nephews, and children of lifelong friends) without being shamed, shunned, and banished from the community.

So, according to the standard narrative, as male parental investment translates into advantages for that man’s children (more food, protection, and education—other kids be damned), women would have evolved to choose mates with access to more of these resources and whose behavior indicated that they would share these resources only with her and her children (indications of selective generosity, fidelity, and sincerity).

But, according to this narrative, these two female objectives (good genes and access to a male’s resources) create conflictive situations for men and women—both within their relationship and with their same-sex competitors. Wright summarizes this understanding of the situation: “High male parental investment makes sexual selection work in two directions at once. Not only have males evolved to compete for scarce female eggs; females have evolved to compete for scarce male investment.”¹⁴

“Mixed Strategies” in the War Between the Sexes

It’s no accident that the man who famously observed that power is the greatest aphrodisiac was not, by a long shot, good-looking.¹⁵ Often (in what we might call the Kissinger effect), the men with the greatest access to resources and status lack the genetic wealth signified by physical attractiveness. What’s a girl to do?

Conventional theory suggests she’ll marry a nice, rich, predictable, sincere guy likely to pay the mortgage, change the diapers, and take out the trash—but then cheat on him with wild, sexy, dangerous dudes, especially around the time she’s ovulating, so she’s more likely to have lover-boy’s baby. Known as the mixed strategy in the scientific literature, both males and females are said to employ their own version of the dark strategy in keeping with their opposed objectives in mating (females maximizing quality of mates and males maximizing quantity of mating opportunities). It’s a jungle out there.

The best-known studies purporting to demonstrate the nature ofthese two differing strategies are those done by David Buss and his colleagues. Their hypothesis holds that if males and females have conflicting agendas concerning mating behavior, the differences should appear in the ways males and females experience sexual jealousy. These researchers found that women were consistently more upset by thoughts oftheir mates’ emotional infidelity, while men showed more anxiety concerning their mates’ sexual infidelity, as the hypothesis predicts.