Monday, April 16, 2007

Heights of daredevils: shorties get the girls Send this entry to: Spurl Ma.gnolia Digg Newsvine Reddit

To expand on the findings of a previous post on shorter guys dominating the pretty boy and hip hop niches, itself inspired by a discussion at Steve Sailer's blog on short guys dominating the rockstar niche, let's now consider the average height of males who specialize in another show-off niche: daredevils. Since performing physically dangerous stunts must require a certain degree of athleticism, you might think that daredevils would tend to be taller than average, as in basketball, football, and other popular sports. On the other hand, perhaps what counts more than height or dominance are nimbleness, ability to maintain one's balance, and being a smaller target (e.g., when being charged by a bull or having darts thrown at one's body). To investigate, let's have a look at the heights of the main cast of the popular MTV daredevil show Jackass. [1] Examining just the hardcore, professional members:

Jason Acuña - 4'7
Bam Margera - 5'8
Chris Pontius - 5'8
Preston Lacy - 5'8
Ryan Dunn - 5'9
Brandon Dicamillo - 5'9
Steve-O - 5'10
Dave England - 5'10
Johnny Knoxville - 6'0.5
Ehren McGhehey - 6'1

Using the data at the excellent website, I could only verify the heights of Knoxville, Margera, and Steve-O (in the thread on Knoxville). The other heights are from their entries, and so are probably exaggerated by 1 inch or so (this is clear from comparing cast members when they stand side-by-side in stunts). Making no adjustments, and leaving aside the outlier of Jason "Wee Man" Acuña (a "little person"), the mean here is 5'9.7; while reducing the unverifiable heights each by 1 inch gives a mean of 5'9.1. For American males age 20-39 (see the PDF here, p.10), mean height is 5'9.6, based on a sample of 1441. I assume the SD for height of the general population is 3 in., though the test is not affected by any reasonable choice. We accept the null hypothesis of no difference in means between daredevils and a random sample of males, regardless of whether we use the unadjusted or adjusted data (both p greater than 0.6 using a two-tailed t-test). Even norming to non-Hispanic White height does not make the results significant (p ~ 0.3). Admittedly the n is small, and perhaps a larger dataset on professional daredevils would resolve the issue of whether there truly is no difference or whether the non-significant trend toward shorter stature here is actually significant.

Looking at a related group of elite athletes in "extreme sports" such as skateboarding and BMX (rather than the all-purpose daredevils of Jackass), I found this handy webpage for a star-studded event that includes height info. NB: Tony Hawk is actually ~6'2, not 6'3 as reported at the above website (let alone the claim of 6'4 at, according to several profiles (e.g., this one and this one), and by comparing him and Johnny Knoxville when they stand side-by-side in a stunt for Jackass Number Two. It's always safer to round down when we're talking about self-reported male height. Comparing the mean of these 15 males -- 5'9.3 -- with that of the aforementioned representative sample of American males, we again accept the null hypothesis of no difference in means (p greater than 0.7 using a two-tailed t-test). As with the stunts of "well-rounded" daredevils, those of the specialists too do not appear to demand taller or shorter than average height.

So, if daredevils tend to be of average height, why the insinuation in the title of the post that they qualify as "shorties?" In the mating arena, the minimum height for an American male to qualify as a "good blind date" is probably 6' or 6'1, so that men who are shorter than this must make up for it somehow. For example, a study of online dating outcomes (PDF) suggested that a 5'10 male would have to earn $32,000 more than a man of 6' in order to receive the same amount of attention from women. The idea is that females are more concerned with quality than quantity of mates, so that they focus on traits as proxies for quality. Since it's rare to find a male who scores highly on all desirable traits, most women face a trade-off between competing "almost dream guys."

Being a professional daredevil is a pretty easy way to signal your genetic quality -- only the truly blessed can perform one dangerous stunt after another without being disfigured, mamed, paralyzed, or killed (watch the bloopers reel for amateur daredevils and see). You need at least general intelligence, boldness and risk-taking, and physical deftness / coordination. So, this could be another instance of the Handicap Principle. Once the first few daredevils in history figured out that they could impress girls as sex symbols, they would have had more children than the population average, increasing the frequency of alleles implicated in the relevant traits. This logistic growth would have continued until their niche became saturated (i.e., when it would pay off more to specialize in some other niche than join the daredevils). Again, it's hard to attention-whore when everyone is exhibitionistic in the same way. [2] This show-off quality is what distinguishes the daredevil niche from others that might also preserve variation in daredevil-ish traits, such as that of young soldiers (cannon fodder). By hypothesis, daredevils are more narcissistic than soldiers.

These processes will maintain genetic variation in traits such as excitement-seeking and height when other pressures might want to erode such variation; e.g., females might in general want a 6' partner or a cautious father of her children. In the comments of a related post on the heights of female sex symbols, Jason asked whether the trend toward shorter male height was an effect of production companies wanting to minimize the height difference between male and female stars, preventing awkward shots. The data on daredevils suggests that this is not a reason, as they rarely appear kissing females on film, and the same is true of rockstars.

And returning to another post on the role of technology in preserving variation, new technology will help people to identify who is cut out to be a daredevil since most stunts involve taking punishment from some product of human artifice, taunting but escaping from a deadly predator using technology, and in general using technology to push the limits of human performance. Now, this is not to say that pre-industrial individuals were jumping off cliffs with a parachute, but the Spanish matador requires only a sword (and really a stick with a large, sharp arrowhead might do). Also, Jackass members Chris Pontius and Steve-O developed their own daredevil show, Wildboyz, in which they often don't use technology at all, but rely on withstanding assults from wild animals (e.g., having their buttocks stung repeatedly by scorpions or surviving a swim with killer sharks). So, there's no reason this dynamic could not have started tens of thousands of years ago, although surely recent history, during which human beings have radiated into a myriad of diverse physical and social environments, will have created different frequencies of such traits between populations. [3]

We now turn to the question of whether daredevils actually do manage to mate with top-choice females, since status per se isn't attractive (as Half-Sigma likes to point out w.r.t. World of Warcraft nerds). Here are some photos of the girlfriends / wives of the sub-6' daredevils:

Bam Margera's wife
Bam Margera's former fiance
Chris Pontius' wife
One of Steve-O's girlfriends (others)
Best example: Wee Man's girlfriend (see pics "w/ Trisha")
Dave England's wife
Dave Mirra's wife (in the middle)
Carey Hart's wife is singer Pink
Bucky Lasek's wife

Perhaps more important than quality is quantity of mates, since the latter is more of a limiting factor on male reproductive success. Steve-O says here that he often sleeps with groupies, and judging from the friends on the MySpace pages of the Jackass members, their groupies are plenty -- and plenty attractive. On a final note, the shorter male readers should take this into account when encouraging your sons to take up one activity or another: if you want them to be successful with females, they'd better train hard to enter a niche that's tailored to short or average-height guys.

[1] No student of human biodiversity can forever avoid pop culture icons, filled as their ranks are with freaks and deviants of all kinds. The only DVD I've ever bought is Jackass Number Two, which I highly recommend to all the young male readers, if you haven't seen it already. The DVD contains lots of bonus footage, too. It is easily one of the most hilarious movies I've ever seen. For those who are unfamiliar with the material, here are a few illustrative examples from YouTube (both NSFW): here and here.

[2] Another clear example of the exhibitionistic appeal of the Jackass members is that they frequently engage in very homoerotic behavior, although none are gay. This is like the increasingly large group of straight girls in college (and, I hate to think, high school) who conspicuously make out with each other at parties (leks) in order to monopolize the attention of the alpha males.

[3] One puzzle is why sub-Saharan Africans are not only underrepresented among daredevils, but are positively freaked out as a group by the idea. (Watch any black stand-up comic show long enough, and soon you'll learn that they love to joke about how insanely death-defying White people can be, in contrast to the sensible Blacks. Another frequent topic is that White people stick around to find out what's going on in a calamitous situation, whereas Blacks immediately get the hell out of there.) This is a puzzle because they are well represented in most other show-off niches such as dancers, singers, athletes, models, and so on. Two possible reasons for this are the aforementioned aversion to "danger in nature," as well as their group's mean IQ of 85. Again, part of the daredevil appeal is that you rely on smarts to avoid accidents. Linda Gottfredson recently argued that avoidance of accidents was part of the reason why human beings became more intelligent (her first paper under 2007). The Jackass members are smart enough to pass high school-level classes at least (though Chris Pontius dropped out); Steve-O attended the University of Miami for a time, and his father is a high-ranking business executive.

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Sunday, April 15, 2007

Female sex symbols: somewhat taller than average Send this entry to: Spurl Ma.gnolia Digg Newsvine Reddit

A recent John Tierney blog entry cited a much discussed study of online dating behavior (PDF), which suggests that shorter than average women have it easier in the online dating market, with the ideal height being about 5'2 - 5'3, and taller heights incurring increasingly greater costs. [1] However, women clearly vary in height well outside this range, so something is responsible for so much variation in height being maintained. Here I examine a fairly obvious, partial reason: being somewhat taller than average pays off if a woman is specializing in a niche that depends on sex appeal, in particular sex appeal that incorporates a fair amount of moxie / aggressiveness.

To test this hypothesis, I used to determine the heights of the women listed in the Maxim 2006 Hot 100 ranking. It's somewhat of a "sample of convenience," but it's hard to argue that the women there aren't sex symbols or that Maxim has an irrational bias toward women of a certain height. I could only find data for 77 of them [2], which you can see below the fold. [3]

The above frequency distribution by two-inch blocks (up to and including the right endpoint) shows that the heights of sex symbols are approximately normal (skewness = 0.07, or essentially symmetrical), with mean = 65.6 in. and SD = 2.8 in. A representative sample (PDF p.10) of 1,371 US women aged 20-39 showed that their mean height is 64.1 in., making sex symbols on average 1.5 in. taller than the average American woman. Using any reasonable estimate of variance in the general female population, a two-tailed t test shows that this difference in means is significant (t = 4.5, p less than .0001 -- perhaps lower; my calculator cut it off there). Clearly, being a bit taller than average helps in becoming a sex symbol. But does it matter even within the sex symbol set? Not really. Here is rank in the list as a function of height:

The Spearman rank correlation coefficient between height and rank in the list is 0.14 but is not significant (p greater than 0.2). So, being a bit taller than average probably helps you get noticed, but it is not of central importance. Note, though, that the non-significant relationship is not due simply to a restricted range for height in this sample -- the SD of 2.8 in. is close enough to the commonly used estimate of 3 in. for the general population.

Having established the greater average height of such women, what accounts for this pattern? This tends to be the most bullshitty part of a report, so I'll just throw out some guesses, and readers can add their own two cents in the comments. (Apologies for not researching / citing this section, but my hunch is that it'd be easy to dig up a few references for and against each of the guesses, as the "why" is always harder to pin down.)

Conjectures that assume there's something sexy about tallness per se:

- Longer legs. My eyes feast upon other parts, so perhaps in the comments the leg men can explain the appeal of long legs.

- Greater height tricks the eye into seeing a thinner figure. Fatter is usually not sexier (unless it's fatter than Kate Moss), since it reflects poorer health.

Conjectures that assume height isn't sexy per se, but that it covaries with some sexy other traits:

- Greater height could reflect a higher degree of male-typical hormones, which would aid the female in projecting the less passive / "take what she wants" attitude that characterizes sex symbols.

- Greater height could reflect better nutrition and healthy development in general -- think of all those Midwestern model types who grew up away from pathogen- and- toxin-infested urban areas. Good health is sexy per se.

A conjecture that assumes height isn't related to sexiness at all:

- Greater height is necessary to stand out from the crowd and intimidate other women in the entertainment industry. Maybe the average guy couldn't care less about a woman's height, but to break through and survive in a cut-throat industry, sheer height helps.

Whatever the reasons turn out to be, it's clear that there are reproductively prosperous niches that taller than average women are suited to, so that some genetic variation in height will be preserved despite males' apparent greater interest in females who are 5'2 - 5'3. Presumably the same is true in the other direction: former rockstar Shakira says here that being petite (she is ~5'1) causes men to act protective around her. Petite women might have a more sprightly, giggly appeal; so, alleles for shorter height could be preserved either due to the sexiness of girly girls or due to their receiving more protection and investment from others because of their pedomorphic stature.

[1] Oddly, the authors phrase this as a trade-off of height vs. income -- i.e., how much more income would a 5'10 woman have to earn compared to a 5'4 woman in order to garner the same amount of male attention? This makes sense when looking at female preferences since most female online daters are concerned principally with the guy's height and income, and thus face a trade-off should a particular guy not excel at both traits. It makes zero sense to look at male preferences this way, though, since most men are interested in many other physical traits before height even enters their mind, and income and power are not sexy to most men.

[2] I coded the women by rank only, so if a reader wants to know which data are missing, I'll upload the Excel sheet, and they can see for themselves. Almost all of the missing data are from the bottom of the ranking anyway, so the more important points are accounted for.

[3] I took the cited height for granted if it was an integer; otherwise I browsed through the text of the entry and discussion to decide which number was most accurate, sometimes rounding up, sometimes down, and sometimes keeping it as is. (19 of 77 data-points are non-integers, so I didn't round indiscriminately.)

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Tuesday, April 03, 2007

Cultural evolution causes biological evolution Send this entry to: Spurl Ma.gnolia Digg Newsvine Reddit

Returning to a favorite theme here -- debunking the balderdash that recent human evolution is cultural rather than biological -- consider how simple technological changes can influence human biological evolution. Take musical instruments: in an environment with no musical instruments, and thus essentially no music, you'd never know who were the rockstars (if male) or the dancing queens (if female). With no way to detect these sexy phenotypes, natural selection could not change the frequencies of alleles that contributed to them. But once the presence of musical instruments becomes a predictable feature of the environment, suddenly there's a pressure to be a good performer, and so traits both physical (dexterity, agility) and psychological (extraversion, emotional volatility) will increase, at least up to a point where any further increase would be a bad bet for newcomers as they crowd an already saturated niche. It's hard to show off when everyone else shows off in the same way.

Now, we commonly urge youngsters to "find their niche," yet many people ignore the obvious corollary of this ecological phrase, namely that whatever cultural processes spawn new niches will also result in a change in frequency of alleles implicated in the traits needed to thrive therein. Unlike Darwin's finches, humans don't need to expand into an unsettled archipelago to undergo adaptive radiation -- we can stay fixed geographically but broaden the range of niches in our "social-cultural space."

At my personal blog, I sketched out a reason for why technological progress tends to be more bustling than progress in more abstract disciplines like geometry, where progress appears to stagnate for quite awhile until "the next big thing" comes along. Basically, the purer arts and sciences are the hobbies of weirdos, whereas technology is usually a matter of life and death: i.e., outperforming the technology of your adversaries. This literal arms race keeps the pace of technological progress much more frenzied than in other cultural areas. The key is that new shields, spears, guns, and ships don't affect the fitness of just soldiers, because most of this new stuff will be ripped off by others to innovate civilian life.

For instance, there would be no common cars if militaries had not pioneered the technology of interchangeable parts and mass assembly-line production for ships and firearms. Nor could their interiors and exteriors be held together were it not for the common use of steel, an alloy whose first modern production method -- the Bessemer Process -- resulted from its inventor's efforts to more efficiently produce firearms for the Crimean War, and whose Captain of Industry (Andrew Carnegie) made his fortune through contracts to build warships for the US Navy. And since the widespread availability of the automobile, many males have carved out a niche whose appeal to females centers around owning a car when other males don't (the guy in 10th grade with his own car) or using their car to signal machismo (drag racers). So, to paraphrase a related slogan on technological changes fueling biological changes: howitzers hatched heart-throbs in hot rods.

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