The sexually-successful-son hypothesis

A well-known hypothesis in evolutionary theory is the sexy-son hypothesis (Weatherhead & Robertson 1979). It states that a female will sexually prefer males who are sexy, because this preference ensures sexier male offspring, which in turn will propagate the female’s genes more effectively.

An intriguing circularity

The hypothesis is clearly circular: It explains female sexual preference as a preference for sexy males (whose sons will be more likely to be sexy). But whatever males conform to female preferences are by definition sexy. So the hypothesis can be restated as follows:

Females prefer males that females prefer.

Perhaps this circularity should not be seen as a logical flaw, but as reflecting the causal loops inherent to these processes. In particular, females will prefer males that other females prefer.

Objective-trait preference versus female-judgment-copying

Any objective-trait preference (say a female preference for dark hair) is consistent with the sexy-son hypothesis, as long as the preference is widespread in the female population. (Dark hair is an objective physical trait. If most females find dark hair sexy, then finding dark hair sexy will be evolutionarily advantageous to a particular female.)

However, the sexy-son hypothesis is also consistent with a more generalized female preference mechanism: beyond any innate preferences for particular objective traits, the female may have a preference for any trait at all that she perceives to be preferred by other females. This is the female-judgment-copying variant of the sexy-son hypothesis.

At the level of group selection, such an abstract and flexible sexual preference mechanism may rapidly promote the genes of a group of males who suddenly achieved some cultural success (e.g. developed a tool or technique), because it would enable female preferences to self-organize and unify within a single generation in favor of the males in question.

It is imaginable that an initial nonsexual preference becomes sexualized in a self-organized manner: For example, a particular female may choose a male based on a nonsexual judgment (e.g. cultural achievement). Another female perceiving this may then become sexually attracted to the male or his most salient qualities.

Females may prefer natural or cultural male traits

The preferred traits could be natural or cultural, whether females have innate preferences for certain objective traits or a tendency to copy other females’ preferences. However, a tendency to copy the judgments of other females (or of conspecifics in general) may offer the more straightforward account for sudden strong sexual preferences among females for males with certain cultural distinctions (celebrities, rock stars, as well as members of respected groups).

Should the sexy-son hypothesis be replaced by a sexually-successful-son hypothesis?

What ultimately matters to the propagation of the female’s genes is not whether her offspring will be perceived as sexy, but whether her offspring will be sexually successful.

Consider a son who is not sexy in any conventional sense but seductive nevertheless: He is quite likely to successfully propagate the female’s genes. Next, consider a sexy son with no sex drive: He is not likely to help propagate the female’s genes. Next, consider an unsexy son with strong rapist tendencies: He is more likely to propagate the female’s genes.

Strong sex drive and even rapist tendencies may lead to a more effective propagation of the female’s genes, so a female sexual preference for these traits may be evolutionarily successful.

This suggests that the sexy-son hypothesis should be replaced by a sexually-successful-son hypothesis and may explain the widely noted female preferences for male promiscuity and male physical dominance during sex.

8 Responses to “The sexually-successful-son hypothesis”

  1. 11minutes Says:

    “Females prefer males that females prefer.”

    from a logical point this means:

    sexy-son hypothesis == sexually-successful-son hypothesis

    What made me think is that it is like a runaway selection gone wild.

    Male peacocks are believed to have those outrageous tails because female peacocks prefer them big (sexual selection). This results in peacock females being attracted to the same male peacocks that other females are attracted to.

    But biologists believe this is the proximate cause only. The ultimate cause is that a long tail is a handicap and therefore indicates increased fitness.

    For human females the strongest attraction trigger seems to be the desire of other women (call it preselection or social proof or whatever). It is like a peacock’s tail. In your logic it is both, proximate and ultimate. It is like a shortcut of the runaway selection that occurred in peacocks.

    The more women sleep with men who sleep with many women, the more fit these men are!

    So humans – having the luxury of language and small social networks – can get rid of the peacock tail and go directly for the group decision of who’s hot.

    What defines then the group decision?

    Is it a man’s own judgment of himself only? Or is it only the circumstances that lead some men to be more desired, which will catapult them in a positive feedback loop onto the thrown of sexy men?

    Or are there other factor – not unlike the peacock’s tail? What about the level of free testosterone (or the muscularity associated with it)? What about height? The confidence that comes with these attributes?

    If any of these count, why would women not go for these traits directly, but use the group decision of other women?

  2. stagetwo Says:

    you write: ” “Females prefer males that females prefer.” from a logical point this means: sexy-son hypothesis == sexually-successful-son hypothesis”

    this logical implication only holds if you assume that female choice alone determines male sexual success. but the sexy male, could be uninterested in sex (sexy but not sexually successful). and the unsexy male could have sex by coercion (unsexy but sexually successful).

    to be sexy means to be preferred by females. to be sexually successful means to have sex (involves male desire, and can involve coercion).

    the sexually-successful-son hypothesis includes the less savory aspects of sexual success (because sexual success not mere sexiness determines the path of evolution) and may explain why those less savory qualities are possibly also female sexual preferences.

  3. stagetwo Says:

    regarding the peacock’s tail, there may be something to the idea that a big tail suggests that its bearer can “afford” to have it.

    however, such an “ultimate cause” in terms of fitness is not strictly required for such traits and preferences to develop in a process of runaway sexual selection. the ultimate-cause explanation assumes that there is a concept of fitness that excludes sexual selection. but sexual selection is always part of the environment, which defines fitness. therefore, run-away sexual selection can, in principle, produce preferences for arbitrary features that are not indicators of any type non-sexually defined fitness.

  4. 11minutes Says:

    regarding the peacock’s tail, there may be something to the idea that a big tail suggests that its bearer can “afford” to have it.

    however, such an “ultimate cause” in terms of fitness is not strictly required for such traits and preferences to develop in a process of runaway sexual selection.

    This is absolutely correct.

    One could speculate that women prefer males with high testosterone qualities (assholes/bad boys) because they are handicapped by their risk-taking behavior, but low testosterone seems to be a higher risk factor in reality.

    The question remains how women select men in the first place (and why some traits such as height and confidence are universal attraction switches) – if they all wait for another woman’s decision, they would get stalled.

    You could assume the following scenario:

    Take a set of women who get introduced to a group of guys.

    In the beginning some women will find some guys (randomly) more attractive than others. They do not agree on who if the most attractive guy.

    The attraction of some women will cause other women to be more attracted to the same guy. This way random fluctuations will get amplified to macroscopic differences.

    The more women get attracted to the same guy, the more other women will join in. Eventually, there is a group decision on who is the most attractive guy.

    That might be exactly what’s going on at bars and clubs – at least to some degree.

    This is why it is hard to get a same night lay when showing up late at a bar, and ridiculously easy when you show up with pivots and banter your way around the bar.

    Life in general will produce “naturals” this way, because some guys will get female attraction early on and this gets amplified to ridiculous levels as they get older.

    I am not denying that women – desperate for clues as to what the other women like – will look at a man’s body language, height, handsomeness and even his crotch (pretty much in this order) to gauge him up.

    But when you ask girls why they like tall men, they typically reply “I want to look up”/”feel secure” etc., which makes you wonder why short/petite girls have the same preference. It is at that point that women often admit that it is more about what the other girls think…

  5. Is there Anything Good about Men? « eleven minutes Says:

    [...] is that the number one factor that women seem to select for is how many other women want a guy (“sexually successful son hypothesis”). In other words, men do not need to be extremly dangerous or sensitive. They just need some way to [...]

  6. someone Says:

    “The attraction of some women will cause other women to be more attracted to the same guy. This way random fluctuations will get amplified to macroscopic differences.”

    This would also nicely explain boy bands and the mass hysteria they cause.

  7. Artful Dodger Says:

    Another interesting post. Roissy seems to take the position that women are always attracted to the badboy alpha male and only consort with beta male providers (doctors, lawyers, and other assorted professionals) once age has lowered their sexual market value.

    Do you think it might be the case that women are pursuing these guys not to cuckold them, but rather because the standard for “alpha” is different in their late 20s? In other words, adopting your “female judgment-copying theory,” women actually become sexually attracted to these men because that’s what all of the other women are pursuing at that age. Just like all women were pursuing the captain of the varsity football team at 16?

    • stagetwo Says:

      that’s a good thought. but doctors and lawyers are potentially sexy for being powerful. they will be actually sexy to the extent that they project power also in conversation and all the way through to actual sex. it’s not the provider traits that make them sexy, but the power. at the same time, as you say, the high-market value, is sexy, perhaps because it is the deepest and truest form of power in a relationship.

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