RSS
In an interesting paper published in the Jan, 2007 issue of Hormones and Behavior, researchers describe a phenomenon they claim is unique to human females; their overt display of fertilty. Specifically, around the time of maximum fertility, women show enhanced “self-grooming” behavior and dress in a more provacative manner in an apparent attempt to solicit copulations. Even more interesting, and in support of a claim I have made previously, is that even females in long term “monogamous” relationships exhibit these behaviors. (difficult to imagine how or why behaviors like this would evolve under the humans are monogamous hypothesis)
I’ll just remind people that while the idea of unconscious regulation of overt behavior that enhances host reproductive opportunities, there are even cooler stories where parasite infection effects sexual behavior similarly.
While this is an intersting study, one might ask the following additional questions:
- Does the magnitude of solicitation depend on the quality of either the existing mate or extra pair mate? If this is an adaptive behavior, you would predict that solicitation should increase as existing partner quality decreases or as extra-pair mate quality increases.
- Is there a difference in male perception of this solicitation when looking acoss male quality or relationship status?
- Does solicitation vary with MHC genes? (Do Women with rarer alleles solicit less?)
- How might one get a judge-jobs? “hot-woman photograph evaluator”
Any interest in replicating this here at GNXP? Women- submit randomly chosen photos to me or to Razib, one just after your period (low fertility), one about 2 weeks later (peak-fertility). We can assemble an “expert panel” of judges to evaluate …
Paper Abstract (and doi)
Humans differ from many other primates in the apparent absence of obvious advertisements of fertility within the ovulatory cycle. However, recent studies demonstrate increases in women’s sexual motivation near ovulation, raising the question of whether human ovulation could be marked by observable changes in overt behavior. Using a sample of 30 partnered women photographed at high and low fertility cycle phases, we show that readily-observable behaviors – self-grooming and ornamentation through attractive choice of dress – increase during the fertile phase of the ovulatory cycle. At above-chance levels, 42 judges selected photographs of women in their fertile (59.5%) rather than luteal phase (40.5%) as “trying to look more attractive.” Moreover, the closer women were to ovulation when photographed in the fertile window, the more frequently their fertile photograph was chosen. Although an emerging literature indicates a variety of changes in women across the cycle, the ornamentation effect is striking in both its magnitude and its status as an overt behavioral difference that can be easily observed by others. It may help explain the previously documented finding that men’s mate retention efforts increase as their partners approach ovulation.
English
Arabic
Chinese (Simplified)
Dutch
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Persian
Polish
Portuguese
Russian
Spanish
Swedish
Turkish
Vietnamese
Even in a monogamous relationship, a woman may (genetically) benefit from being increasingly attractive at times of peak fertility.
If grooming and flirtatous behaviour have a cost (as anyone who has ever priced cosmetics would attest) then it is logical that such behaviour should be rationed to maximize sex at the most fertile time.
This is true regardless of whether it is sex with a stable partner, or with someone else.
Hence your comment that “difficult to imagine how or why behaviors like this would evolve under the humans are monogamous hypothesis” does not follow.
Does the magnitude of solicitation depend on the quality of either the existing mate or extra pair mate?
If she’s prettying herself up to get an extra-pair mate’s DNA, then she’s looking for something she doesn’t already have at home. But because many traits affect male desirability, it’s unlikely that her current mate satisfies them all. He’s not going to be +2 SD in IQ, height, penis size, and wealth. So the experiment would have to look at all these — do women with short men pretty themselves up at peak fertile phase? Probably, to get a tall guy’s genes.
And so on for the other traits: you’d have to calculate “quality” across the relevant traits, and then you might see a pattern where mates of guys who have it all don’t feel like straying, mates of total losers are the most eager to mate on the sly, and the rest in between.
Returning to the height / environmental heterogeneity post, this is likely a reason why males are so much more variable than females: there are more ways for a male to be sexy and succeed (smart, creative, tall, rich, well-endowed, etc.) than in the female case (outward attractiveness).
Does solicitation vary with MHC genes? (Do Women with rarer alleles solicit less?)
The MHC / sexual selection stuff will, I predict, be revealed to be a mostly false positive result. Or it will account for a tiny fraction of the variance in sex appeal / relationship satisfaction / etc., 1% or less — at least in most of the West (see below).
The reason is simple: MHC loci are among the most polymorphic in the genome, so between any two random individuals, at a given locus, deviation from homozygosity is overwhelmingly likely (minus potentially inbred communities like the Hutterites). So, to see if there’s even more deviation than expectation — which would be a very subtle difference — you’d need to type lots of loci, not just 3 (as in the 3 “famous” MHC / sexual selection studies — the t-shirt odor ones, and the recent one on relationship satsifaction), and you’d have to examine a large number of people, not ~50 (as in these cases).
Another good idea would be to test a population that’s actually expected to satisfy the conditions that the model assumes cause the behavior. In the MHC case, the putative cause is resistance to pathogens — why would you study the Swiss, then? (Both sexy t-shirt studies were done among German Swiss students.) You’d want to study Brazilians or Indians. I’m sure you’d get better results. For your question, there’s anecdotal evidence that Brazilian girls turn up flirtation even more when they’re around foreigners, but again, you’d want to get a large sample and type a large # of MHC loci.
Not to sound mean, but given the track-record, I’d take sexual selection-related studies from the evo-psych peeps at U of New Mexico w/ a grain of salt until there’s careful, independent confirmation. I’m writing up a big post on symmetry & sexual selection, so I’ll flesh out the details later.
a phenomenon they claim is unique to human females; their overt display of fertilty
you mean their lack of an overt display of fertility? chimps get all swollen up and red downstairs when fertile; human ovulation is generally considered “cryptic”; i.e. neither the woman nor anyone knows when she is ovulating. this paper and other make it clear it’s not completely cryptic, but it’s nothing like chimps.
good point.
I’m skeptical of the claim that monogamy would make this adaptation useless. But Patrick already said it better.
Patrick:
The point was that advertising fertility outside the pair bond is not adaptive in genetic monogamy??
Yes, indicating fertility might be selected within a pair bond- but Im not so sure that it is as simple as looking at the costs of showing.
Agnostic:
Does the magnitude of solicitation depend on the quality of either the existing mate or extra pair mate?
Yes, you’re hitting on my point. Probably advertisement increases when existing mate is of low quality or compatability. They dont specifically test this hypothesis, although it would’ve been nice if they had.
p-ter:
Thanks for correcting- my bad.
“One of the most noteworthy differences between humans and other closely related primates is the absence of clear advertisements of fertility within the ovulatory cycle”
Probably advertisement increases when existing mate is of low quality or compatability. They dont specifically test this hypothesis, although it would’ve been nice if they had.
xpression.pdf
An abstract I read appears to address that point …
As predicted, however, these effects were exhibited primarily by women who perceived their partners to be low on hypothesized good genes indicators (low in sexual attractiveness relative to investment attractiveness).http://www.sscnet.ucla.edu/comm/haselton/webdocs/ConditionalE
This is in reply to agnostic’s post.
A friend of mine once had relations with a married woman. The poor guy ails to this day about the mess. Anwyays, in his defense, she hid her status until after the initial “act.” Her cuckold/husband was a simple Colorado outdoorsman type who had never left the country and who didn’t finish college. My friend was the opposite. excercise was of the indoor sort, spoke 5 languages, was from the East Coast, and had two graduate degrees. She told my friend her husband was “stupid.” My friend was into it because he had the best of both worlds: good sex and little drama – at least initially. The cheating woman soon dumped hubby for my friend and six months after the divorce, she cheated on my friend for his opposite: a rich guy who had never worked out in his life but was the jokester (alpha male) in his circle of friends.
So here, anecdotally, we see a woman going from men who had comparative appeal in terms of first, being outdoorsy/rugged to second, high IQ to finally, rich/status.
If monogamy doesn’t exist, how did the ritual of marriage come to exist? It seems strange that almost every culture throughout history made such a big deal about staying true to their spouse. Humans must have been really good at fighting the instinct of polygamy, and for no apparent reason, instituted monogamy into law and religion for thousands of years. How did monogamy come to exist if polygamy is instinctive? Why do humans have such strong emotions when they discover their spouse is cheating, after all, if it is instinctive to have more then one spouse, despite the fact that cheating is shunned in society, we wouldn’t care if our spouse is cheating or if we are caught cheating, right?
I know Peter Frost has theorized that certain environments made polygamy difficult (possibly resulting in Steve Sailer’s “jealousy belt”). It doesn’t seem implausible that those memes could be sucesfully spread to people with a history of polygamy.
I’m curious about whether the woman’s age and number of kids affects this. If she’s 35 and doesn’t have any kids yet, there’s a good chance (in any society without birth control) that her husband is sterile. In fitness terms, there is then zero cost to her cheating. (She might also be sterile, but then there’s still no fitness cost.)
Similarly, with two or three kids from her husband, she’s investing all her fitness in his genes. Perhaps there’s an incentive to cheat at that point to get at least one kid with a different mix of genes.
Has anyone done empirical studies on the claim that women who have just become pregnant are especially attractive? I’ve noticed that effect, and I’ve always heard about it (“the glow”), but I don’t know if anyone’s ever verified it experimentally.