I was just flipping through "The Intertwined Evolution of Narcissism and Short-Term Mating" by Holtzman and Strube (full PDF here) in hopes of tracking down references on the evolution of long-term human pair bonding.

I found this interesting summary of earlier work:

Phylogeny aims to identify the historical emergence and development of traits in light of physical evidence (e.g., from skeletal remains and fossils records). Trait emergence tends to happen slowly, as the genome is gradually modified within existing constraints (Gould, 1989). One constraint on human evolution 1.5 million years ago was that, up until that time, the primary traits under positive selection were attractive and contentious traits—two that had encouraged dominance. The two primary selection pressures before that time were sexual selection (requiring attractiveness; Frederick & Gallup, 2007) and intrasexual competition (requiring contentious traits: Eastwick, 2009). Thus these positive selection pressures constrained the evolution of novel human traits. However, as Eastwick (2009) describes, beginning in this time humans no longer were strongly sexually selected for symmetry in body features (Frederick & Gallup, 2007), indicating decreased selection for attractiveness (although it remained important). Further, the average sex-differences in skeleton sizes from this period are smaller than the sex-differences in skeleton sizes from before then (McHenry & Coffing. 2000), indicating decreased selection for males to be larger, quite possibly reflecting decreased selection for intrasexual competitive advantages. A decrease in symmetry and a decrease in gender-differences in size provide converging evidence that selection pressures on dominance-related traits had changed. After this time, it is therefore argued (Eastwick, 2009, Table 2) that a primary trait under positive selection was cooperativeness—facilitating bi-parental care, attachment, and pair-bonds. This was a key turning point in human evolution.

So far, this sounds vaguely plausible and rather interesting. Symmetry is a very expensive signal of reproductive fitness, because it's very hard to perfectly symmetrical unless everything goes right. Apparently our ancestors were a lot more symmetrical 1.5 million years ago, and the men were bigger relative to women. So basically we're talking about really built males with good facial bone structure who gradually started becoming less common, suggesting that females were reproducing less with "alpha" males. Of course, at that point, we're still talking about Homo erectus, who got outsmarted and curb-stomped by good old Homo sapiens.

But as I kept reading the paper, it got sillier and sillier:

PREDICTIONS AND FUTURE DIRECTIONS

Other predictions follow from our evolutionary view, especially regarding effects due to ovulatory cycles, sperm competition, and body morphology. First, if STM shaped narcissism, then narcissists should be exceptional at identifying fertile partners (who can reproduce efficiently), such as narcissistic men identifying women who are in the middle of their ovulatory cycle and thus more likely to become pregnant (Wilcox, Dunson, Weinberg, Trussell, & Baird, 2001). Men do indeed respond to the ovulation of women, by scent (S. L. Miller & Maner, 2010). Pertinent to our hypothesis is whether narcissistic men are better at ovulation-detection than non-narcissistic men, which would enhance narcissists‘ STM prospects. Evidence of special olfactory abilities among narcissists would suggest that STM did shape the evolution of narcissism.

If narcissists have evolved to cuckold other men’s pair-bonded mates (i.e., deceive women’s partners into raising children who are not their own, but rather the narcissist's), then across generations narcissists should have evolved special machinery for doing so. Beginning about 1.5 million years ago, a co-evolutionary arms race may have taken place between people designed for STM versus people designed for long-term pair-bonds. For example, sperm competition among men probably played a significant role in cuckoldry (Shackelford, Pound, & Goetz, 2005). Narcissists may have different sperm qualities than non-narcissists, such as qualities that facilitate rapid fertilization following one-time intercourse. In contrast, non-narcissists may have evolved defensive sperm, more designed to block the successful one-time insemination by male narcissists. Male narcissists may have larger testicles for higher amounts of sperm production, to facilitate insemination. This hypothesis can be derived from the primate literature in which it is evident that STM species tend to have larger testicles (Buss, 2007) Also, male narcissists self-report larger penile size (Moskowitz, Ricger & Seal, 2009); if true, this structure may help remove competitors' semen and increase insemination likelihood for one‘s own semen (Schmitt, 2005; Shackelford et al., 2005).

So, they propose that narcissistic males should:

  • Be better at smelling when women are ovulating, and
  • Have special sperm.

As evidence supporting the latter hypothesis, they point out that

Also, male narcissists self-report larger penile size

Gee, what could possibly go wrong with asking male narcissists to self-report their "penile size"?

Now, in principle, I do agree that the human brain evolved, and that it almost certainly has (multiple) built-in mating strategies. But every time I look at the evo-psych literature, I find these absolute howlers, such as asking narcissists to self-report how well they're equipped.

Please tell me that there's some rigorous core to the field of evo-psych, a group of researchers who weigh evidence carefully and who don't just make up just-so stories about imaginary cavemen.