The How and Why of Sex Differences

Sexually dimorphic psychological adaptations

When Did Evolutionary Psychologists Stop Beating Their Wives?

Critics of evolutionary psychology often end up embarrassing themselves.
Darcia Narvaez
This post is a response to What you think about evolution and human nature may be wrong by Darcia Narvaez, Ph.D.

The recent post by Dr. Darcia Narvaez criticizing evolutionary psychologists was exemplary, but not in a good way. 

It was a good example of how many self-appointed critics of evolutionary psychology often end up embarrassing themselves by betraying a stunning ignorance of the discipline.  They typically set up false dichotomies about nature and nurture (see my previous post about this topic).  And they usually set up straw men by suggesting that evolutionary psychologists believe things that they do not, and then the critics smugly take glee in knocking them down.    My colleagues and fellow PT bloggers have already provided rebuttals to her post, with this response by Gad Saad, this response by Catherine Salmon, and this response by John Johnson.  (Update:  Robert Kurzban has also responded with a bit of humor, by developing the The Pop Anti-Evolutionary Psychology Game.) 

Find a Therapist

Search for a mental health professional near you.

For those who would like to learn more about what evolutionary psychology actually is, I recommend the brief article by Confer, et al., Evolutionary Psychology: Controversies, Questions, Prospects, and Limitations.

Another good source is The Evolutionary Psychology Primer by Tooby and Cosmides. 

Straw man

Others have already pointed out the many stunning errors in Dr. Narvaez's post.  So given the topic of my blog, I will focus here specifically on just a couple of her comments about sex differences.

Navarez: "(Among hunter-gatherers) there was more sexual freedom and mating behavior for all ages, yet EP assumes a scenario like today's of restriction and competition..."

Take a look at the height difference between males and females -- why are males taller?  Those familiar with the process of sexual selection will immediately suspect a likely possibility -- that it is a result of intra-sexual competition among males for mates.  That is, when males are bigger than females, it suggests a polygynous mating system where larger mates were more likely to win physical contests for mating opportunities with females (see my previous post on reproductive variance).  Did human males physically compete with each other?  We can literally see the answer today.

But why do males fight for females, rather than vice-versa?   The technical explanation is that females have a greater obligate parental investment -- in humans, nine months of gestation, followed by three or more years of lactation, and a decade more of socialization.  In contrast, males can reproduce in, at minimum, a few minutes of their time.  Males thus have a faster "reproductive rate" than do females.   Female reproductive capacity is a limited resource, thus, the greater intra-sexual competition among males.

Females do compete for the best male mates as well, but usually not by physical contests.  Females don't mate randomly, and the sexual preferences that females have today are the "psychological fossils" of which choices tended to increase female reproductive success in the past.

Navarez: "Sexual relations were more about pleasure."

I presume that she is contrasting pleasure with reproduction.  This betrays a failure to distinguish between proximate vs. ultimate causality.  Why is sex with an attractive partner in the right circumstances pleasurable?   Because it led to more successful reproduction.  Sex was about pleasure, and as pleasurable, for ancestral humans as it is today.

Navarez: Males who are neglected in early life seem to be much more detrimentally affected than females leading to brain decrements and potential fixations (e.g., on sex; see Martin Teicher's work).

Check out Teicher's study that she linked to -- the study participants were all females!  Perhaps she linked to the wrong study?

I could go on to rebut most every assertion made by Navarez about sex differences today and among ancestral humans.  But, she really has not done her homework on evolutionary psychology or the evolution of sexually dimorphic psychological adaptations.  And,  I am not going to do her homework for her.

Instead let me recommend some readings to her, as well as for any interested readers:

Symons, D. (1979). The evolution of human sexuality. Oxford: Oxford University Press.

Daly, M., & Wilson, M. (1983) Sex, evolution and behavior.  NY: Brooks-Cole.

Mealey, L. (2000). Sex differences. NY: Academic Press.

Low, B. (2000).  Why sex matters. NJ: Princeton University Press.

Buss, D. (2011). Evolutionary Psychology  NY: Bacon.

 

Michael Mills, Ph.D. is an associate professor of psychology at Loyola Marymount University in Los Angeles.

more...

Subscribe to The How and Why of Sex Differences

Current Issue

Dreams of Glory

Daydreaming: How the best ideas emerge from the ether.