Chapter 12- The Psychology of Human Mating
Sexual Selection in Humans
Sexual selection is caused by sex differences in reproductive rate.
A woman can produce only one child annually because her commitment to gestation and preparing her body for another
pregnancy requires about a year. A women’s reproduction is limited by her physiological investment capacity.
Unlike a woman, a man’s fertility is limited by access to fertile women.
North Americans are often surprised to learn that 85 percent of well-described human societies allow polygyny. Monogamy is
evolutionarily novel in human societies.
Even societies that prohibit and punish polygyny are not fully monogamous for two reasons: marital infidelity and the
combination of divorce and remarriage.
A study of remarriage patterns based on data from 47 countries showed that on a worldwide basis, men are more likely to
remarry after divorce than women are.
Human Parental Investment
Parental investment is a technical concept in biology. It includes anything that a parent does for a particular offspring that helps
the offspring and reduces the parent’s ability to invest in other offspring.
When both parents typically contribute, we say the species has biparental investment. Offspring with biparental investment have
Biparental investment is more likely to evolve in species with helpless young. The current idea is that changes in the pelvis
associated with an upright, bipedal gait made it more difficult for our female ancestors to give birth. The solution was to give
birth earlier in the gestational cycle, resulting in smaller but more helpless infants. In this way, the extreme dependence of human
infants may have favored the evolution of biparental investment in our species.
Dynamics of Mating Competition and Choice Humans
Because of a tendency toward weak polygyny, women are expected to be somewhat choosier, men are more competitive.
On average, women are choosier about their sex partners, but men are not wholly indiscriminate.
Fear of dangerous sexually transmitted diseases such as AIDS may have narrowed the gap somewhat, but even as late as the early
1990’s homosexual men were still reporting significant more sexual partners than heterosexual males.
Homosexual and heterosexual men show no differences in their self-reported desire for uncommitted sex, only in their success in
satisfying this desire. This is because gay men are negotiating their sexual activity with other men, whose desires are presumably
Marriage is the result of a successful negotiation between two partners and it is reasonable to assume that each has made some
compromises in reaching this agreement.
Marriage patterns are not a “pure” indicator of mating preferences because marriages involve compromise.
Mates provide two kinds of resources: Genes and parental investment.
The Red-Queen Model
Sex evolved as a defense against rapidly evolving pathogens. This is why we mix our genes with our mates, to change the rules
of the game for our parasites and pathogens.
Mate choice criterion ought to be linked to the ultimate function of sex.
Symmetry as an indicator of Parasite-Pathogen Resistance
Health, vigor, and symmetry are key components of attractiveness.
No face is perfectly symmetrical. However, a number of recent studies indicate that the smaller the deviation from perfect
symmetry, the more attractive the face is judged to be
Research indicates that, among males at least, more symmetrical individuals have first sexual intercourse at younger ages and
have more sex partners over their lifetime.
Complementarity of Immune Weapon
MHC genes build our immune systems. Humans generally prefer mates similar to themselves on a variety of dimensions-height,
intelligence, political views. But the Red-Queen model predicts a mating preference for indi