Why we have pubic hair

A long piece in the New York Times on July 12, "Sex on Campus," by Kate Taylor, was food for thought for a number of reasons, not least because of what it tells us about the evolution of behavior. It's the tale of how, as the writer puts it, traditional sex in college has gone the way of the landline.  She interviewed a number of female students at Penn and she lets them tell much of the story themselves.  
One student says about a guy she hooks up with regularly:

“We don’t really like each other in person, sober,” she said, adding that “we literally can’t sit down and have coffee.”   

Ask her why she hasn’t had a relationship at Penn, and she won’t complain about the death of courtship or men who won’t commit. Instead, she’ll talk about “cost-benefit” analyses and the “low risk and low investment costs” of hooking up. 

“I positioned myself in college in such a way that I can’t have a meaningful romantic relationship, because I’m always busy and the people that I am interested in are always busy, too,” she said.

Until recently, it has been assumed that the "hookup culture", quick sexual encounters of whatever kind, was more satisfying to men than women.  That's because, as we all know, men want sex while women want romantic long-term relationships.  But Taylor's piece makes it clear that women are driving the current trends at least as much as men.  They talk about building their resumes and not having time for relationships.

Evolutionary psychology
The curious thing about this is how thoroughly it runs counter to what evolutionary psychology has been telling us for a long time.  Ev psych is a highly if not hyper-darwinian discipline that essentially tries to explain human behavior as the product of dictates of past natural selection that have now been built into our genomes.  For example, much of ev psych has accepted the premise that it's in females' generally, and hence human females' evolutionary interest to invest in men who will make good fathers for their children, while men never know for certain that a child is theirs and so aren't evolutionarily primed to invest in them or in relationships with their mothers.  Instead they want sex with as many women as possible, to proliferate their genes as widely as possible.  For excellent evolutionary reasons, the idea goes, men have spent eons developing strategies to avoid commitment, and women have spent the same amount of time trying to get them to commit, by hook or by crook.
 
Ev psych has churned out a multitude of theories explaining the evolutionary, adaptive basis for differences in mate choice, mate preferences, and the rates of promiscuity between the sexes. The latest amazing finding is that cunnilingus-assisted orgasm is a "sperm-retention strategy".  Will wonders never cease!

Further, the theory covers such deep theoretical questions as why we have pubic hair -- it's a sexual ornament that indicates sexual maturity and, thus, is attractive to the opposite sex.  But pubic hair itself has gone the way of the landline -- so much for sexual ornaments and indicators of sexual maturity.  It used to be that a woman's ankle could turn a man on, and that was before evolutionary psychology was even a gleam in anyone's eye, so why the field decided that what we find sexually attractive was fixed is anyone's guess.  As Taylor's piece makes abundantly clear, sexual morés are as changeable as the weather, and about as unpredictable!  It's not what we're attracted to that evolved, it's that we're attractable.

More generally, a proper critique of behavior genetics and evolutionary psychology recognizes that most of traits and behaviors they purport to explain long pre-date humans and so can't be analyzed in human-specific terms.  But more important is that if humans evolved to do anything it is to use cognition to evaluate circumstances and adjust their behavior accordingly, rather than to be hard-wired to do specific things.  What we're wired for is to have culture, but culture largely evolves on its own, not because of specific human genes.