Tuesday, May 30, 2006

Thirteen is the sexiest age? I just read Derbyshire's claim that, based on TangoMan's analysis of rape statistics, the peak age for female sexual attractiveness is 12-14. It seems to me that this age range is distorted downward by the fact that children will be overrepresented in rape statistics because when children have any sexual experiences with an adult, it is by definition rape. Adult-adult sex can be consensual--by legal and conventional definition, adult-child sex cannot. The average age of rape is also low because one important contributing factor is vulnerability, and because some rapes may be motivated by factors other than sexual attraction--other factors associated with childhood, such as immaturity.

Does anyone have other kinds of evidence relevant to this issue? One idea I had was to google the terms "barely 18" and "college girls" to get an idea if attraction would be tilted younger or older. The numbers were 479,000 and 3.3 million, respectively.


  1. Well, the most relevant fact would be that most humans are capable of sex and reproduction at age 13, if not younger. Prohibition of sex with or between minors is a completely arbitrary social construct that's arisen within the last two centuries.

    Certainly males are more attracted to younger women, they are wired up to be that way. In our evolutionary past, a 13 year old was a woman in her prime, a 20 year old was an old maid, and a 35 year old was probably dead.

    This evolutionary heritage is still with us. On one level, the adult male who has sex with a 13 year old is merely living the dream. And on the other side of the coin, a 13 year old girl's desire to copulate is perfectly normal. It shouldn't surprise anyone that "rape" of ~13 year olds is more common.

    Laws have moved beyond biology. It really doesn't make a lot of sense. The mindless prosecution of statutory rape cases is embarassing. It detracts from true cases of rape, which are always nonconsensual, frequently horrifically violent and oftentime result in the death of the victim. Contrast the victims of a real rapist with the Tampa teen who was "raped" by his hotty teacher. Scarred for life! Although it's hard to say whether by the teacher or the media circus.

  2. "College girls" seems too broad; no strong sexual connotation. Also, "barely legal" gave 2.6 million. My guess is that the 12-14 cases involve slightly older, slimier high school guys or college freshmen, not 20-something guys or older. I'd peg the female physical prime at 17-22, w/ a 2-year fuzzy zone outside either end of that range.

    There's also a "cheeriness" prime that pretty much overlaps the physical prime, which could be another source of the fascination w/ college coeds -- much more carefree, pleasant, engaging disposition than w/ your average 30-y.o. female.

    A slight correction to compost books' remark -- in our evolutionary past (including until pretty recently), 13-y.o. girls would not have been very sexually mature, since nutrition was shit for most people until the 20th C, when better nutrition lowered the first age of menarche. Before this transition, 13-y.o. girls probably looked like 11-y.o. girls do today.

  3. It's an admittedly crude measure, but you can search the titles of adult films here: http://www.searchextreme.com/index.aspx

    I entered "barely" for those connoting the girl's dangerously young age, and "college" for those connoting the 18-21 range broadly.
    "Barely" got 70 titles
    "College" got 81 titles

    Pretty close, but tilted toward "college."

  4. Fred S.12:25 AM

    I hate to contradict your contradiction, agnostic, but the minimum age for contracting marriage (originally established by the Romans and then adopted by the Church) was 12 for girls and 14 for boys. These were the ages at which children were deemed to have gone through puberty.

    I think that the inductivist is right, insofar as rape has more to do with opportunity than attraction. I'm sure a majority of forcible rapes (rather than merely statutory) are committed by young men against the adolescent children of their girlfriends, while those men are intoxicated.

  5. From 'A Natural History of Rape' (p 163):

    "An individual female's reproductive value (ability to contribute offspring to the population in the future) is at its maximum just after she reaches puberty. As rated by people in general (not just men), this is also when a female's attractiveness is at its peak (Symons 1979, 1995; Johnston and Franklin 1993; Quinsey et al. 1993; Jones 1996)"

    Symons, D. 1979. The Evolution of Human Sexuality. Oxford University Press

    Johnston, V., and M. Franklin. 1993. Is beauty in the eye of the beholder? Ethology and Sociobiology 14: 183-199.

    Quinsey, V., M. Rice, G. Harris, and K. Reid. 1993. The phylogenetic and ontogenetic development of sexual age preferences in males: Conceptual and measurement issues. In The Juvenile Sex Offender, ed. H. Barbaree et al. Guilford.

    Symons, D. 1995. Beauty is in the adaptations of the beholder: The evolutionary psychology of human female sexual attractiveness. In Sexual Nature, Sexual Culture, ed. P. Abramson and S. Pinkerton. University of Chicago Press.

    Jones, D. 1996. Physical Attractiveness and the Theory of Sexual Selection: Results From Five Populations. Museum of Anthropology, University of Michigan, Ann Arbor.

  6. Vol-in-Law3:09 AM

    I think attractiveness varies by culture, nutrition, and racial group/sub-group. One reason the US age of consent is so high at 18 is that it's based around northern European females, who mature later than many other races. That age 12 was marriage age for the Romans isn't surprising - Mediterranean girls mature a year or two earlier than northern-European. Personally I think female attractiveness peaks when the female is fully sexually mature, which is several years after puberty, probably around 18 for northern Europeans, 16 for Mediterraneans.

  7. From the Roman case -- or an even more extreme case where females can marry at, say, age 8 -- we can only conclude that the lawmakers thought this a suitable age to become married, not necessarily to have sex & produce kids. Physical evidence is more reliable than law-makers' opinions when it comes to determining age of first menarche throughout history.

    Another point made in some of the refs that Jason cites is that if rape is more based on opportunity, then rapists would prey on older women who can't fight back, rather than females whose musculature & athleticism are in prime condition for running away or fighting back.

  8. Well thinking about this logically...

    In a society where people had free sex and there was no long term pairing up, men who indiscriminately had sex with women capable of having children would pass on the most genes, so this would be any age range between thirteen and thirty-something when the female reproductive organs become less likely to work effecitvely. In this case there's a heavy penalty for liking girls even slightly below the age of reproductive capability.

    But in a society in which people only had sex within marriage, and stayed married for life, then men who married women who were just reaching the age where they can bear children would have the most offspring so genes encouraging attraction to thirteen-year-olds (the age when girls can begin having children) would be favored. In this case there is little penalty if men like women a year or two before they are capable of bearing children because they will come of age after marriage.

    Both of these evolutionary factors affect men's biologicaly programmed preferences. In neither scenario do men prefer women too old to reproduce.

    Nice blog.

  9. Compost Books said:
    "Well, the most relevant fact would be that most humans are capable of sex and reproduction at age 13, if not younger."

    Speaking about biology only, that may be true, but it isn't a good idea for girls bodies to bear children that young. And the conventional wisdom in my nursing school was that the healthiest babies were born to mothers between 20 and 24. It is so rote that nobody questions it, but I suspect that it is probably about right.

    But back to young teenage mothers. Just one problem that strikes them, but rarely older mothers is developing a fistula. Obstetric fistula mainly affects girls ages 15-19. The UNFPA describes obstetric fistula as an injury to the pelvic organs that most often occurs when a young girl undergoes long and obstructed labor, sometimes for as long as 5 days. Often, the girl is poor and cannot reach or afford the necessary medical care, which then causes her to suffer extensive tissue damage that eventually leads to the death of the baby. Another problem associated with obstetric fistula is that the injury causes women to lose control of their bowels and bladder unless treated appropriately. The urine, and sometimes feces, leaks into the vagina.

  10. I appreciate that this evolutionary heritage is still with us, but I think the early age for menarche only shows that it is the earliest age where there is any advantage for procreation versus morbidity for bearing too early. That doesn't make it the optimum time, though, and it is a wise society that puts these constructs in place. Unlike in many parts in Africa.

  11. By the way, Ron, your Derb link is broken. I should also clear up that Derb was mistaken about Razib. The post he is referring to was by Tangoman.

  12. Fred S.3:20 PM

    Nope, agnostic, twelve is when girls were deemed to be sexually mature in Medeival Europe. Unless you can get a girl from 12th c. Britain on the examining table, one must make use of the resources one has. And these emphatically state that 12 was considered the age of sexual maturity for girls (most marriages were contracted rather later, however).

    It's actually a bit of an exaggeration to say that nutrition was uniformly "for shit" until the twentieth century. The Industrial Revolution actually caused a large drop-off in terms of popular nutrition (as measured by the average heights of army recruits and things like that). It took until about the early 20th c. to catch up to where people had be pre-1750's.

    Well, considering that only 15% of the elderly live with their adult children in the United States, I still think that there will be more opportunity to get at young girls in the situation I outlined. Also, I didn't say that attractiveness played no role, just a smaller one than opportunity.

  13. Yeah, my fault, I thought the secular trend went back farther.

  14. Fidelia said:

    And the conventional wisdom in my nursing school was that the healthiest babies were born to mothers between 20 and 24. It is so rote that nobody questions it, but I suspect that it is probably about right.

    That probably holds true now, and maybe held true then, assuming the woman lived to be 24. But people were getting into the last years of your life by then.

    Re: college girls vs. "barely 18" - - porn in 21st american society is as much about class issues as it is evolution. The "college girl" is an archetype that appeals to both blue collar and middle - or upper class types, for widely different reasons. I think that probably accounts for the popularity of it as a search term.

  15. It's true that mean life expectancy in pre-society were low, even below 30, but the notion that people in their 20s or early 30s were approaching the end of their lives is not. The average gets dragged down by massive infant and child mortality. If you made it past early childhood you stood a good chance of living to a ripe middle age. In 18th century England, for example, about half of 15 year olds lived to 63, and one-quarter to 78, which is not that bad. Earlier periods would have been harsher, of course, but you get the general idea.

    Excellent post here:


  16. for "pre-society" read "pre-modern society".

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