Monday, December 29, 2008

Facial Expressions Of Emotion Are Innate, Not Learned   posted by Razib @ 12/29/2008 11:12:00 AM

Spontaneous Facial Expressions of Emotion of Congenitally and Noncongenitally Blind Individuals:
The study of the spontaneous expressions of blind individuals offers a unique opportunity to understand basic processes concerning the emergence and source of facial expressions of emotion. In this study, the authors compared the expressions of congenitally and noncongenitally blind athletes in the 2004 Paralympic Games with each other and with those produced by sighted athletes in the 2004 Olympic Games. The authors also examined how expressions change from 1 context to another. There were no differences between congenitally blind, noncongenitally blind, and sighted athletes, either on the level of individual facial actions or in facial emotion configurations. Blind athletes did produce more overall facial activity, but these were isolated to head and eye movements. The blind athletes' expressions differentiated whether they had won or lost a medal match at 3 different points in time, and there were no cultural differences in expression. These findings provide compelling evidence that the production of spontaneous facial expressions of emotion is not dependent on observational learning but simultaneously demonstrates a learned component to the social management of expressions, even among blind individuals.

Also see ScienceDaily.


Sunday, December 28, 2008

Episcopalians vs. Jews   posted by Razib @ 12/28/2008 11:58:00 PM

Lots of charts.

City upon a Hill   posted by Razib @ 12/28/2008 09:38:00 AM

Samuel Huntington died yesterday. Though famous for his Clash of Civilizations thesis, more recently he argued for an emphasis on the reality that this (the United States) is an Anglo-Protestant country. But I think that this assertion needs to clarified to a finer grained scale. In Albion's Seed: Four British Folkways in America, the author makes the claim that the culture of the United States is a synthesis of four strands of colonial settlers; New England Puritans, the Lowland Southerners (e.g., Tidewater Planters), the Highland Southerners (i.e., the Scots-Irish of Appalachia) and the polyglot peoples of the Mid-Atlantic (e.g., Quakers of Philadelphia, Dutch Patroons of New York and Swedes of Delaware, etc.). After reading quite a bit of American history, especially the period between 1600 and 1850, I think that over the long haul the concrete political and social realities of America owe much more to New England than the other regions.  After I came to this conclusion (which I will flesh in more detail later), I couldn't help but note that today New England isn't included in the "Real America."


Wednesday, December 24, 2008

The follies of economics?   posted by Razib @ 12/24/2008 11:15:00 AM

Massimo Pigliucci has a post up, Economics learns a thing or two from evolutionary biology. There are many points within the post which I would agree or disagree with, but, I get the sense that the current economic morass is precipitating these sorts of criticisms of "economics." I'm not one to disagree on the importance of behavioral economics, and I believe a serious engagement with the reality that rationality is bounded will only benefit the human sciences. That being said, it seems to me that the current problems are not ones of economics or the economics profession as much as the particularities of the finance profession in terms of its incentive structure. By analogy, imagine blaming zoologists and botanists for the actions of agribusiness (e.g., excessive utilization of antibiotics so as to maximize short term firm productivity at cost to a risk of a high negative externality). Rather than suggest that economics needs to learn from the life sciences (I think this is happening), I believe that you need to look to public choice theory and other extant frameworks available off the shelf.


Sex differences in math?   posted by Razib @ 12/24/2008 11:12:00 AM



Lactase persistence review   posted by p-ter @ 12/24/2008 08:49:00 AM

This is a pretty thorough review of biology and evolution of lactase persistence. It's interesting that the precise genetic mechanism underlying the phenotype remains unknown-this seems like a potentially very interesting model phenotype for people interested in the temporal and spatial regulation of gene expression.


Monday, December 22, 2008

Congenial Times   posted by ben g @ 12/22/2008 09:58:00 AM

Check out Mark Wethman's new quant blog, Congenial Times. It's been around for only a couple of weeks but in that time he's posted a lot of interesting data/analysis on topics ranging from international politics to human biodiversity. His most recent post is on racial differences in educational attainment in Sweden.

The most interesting article to me has been the one on Amish IQ scores. He found data which showed the Amish to have above average reasoning and quantitative analysis skills.* Data like this is essential for anyone trying to understand the Flynn Effect or between-population differences on IQ scores.

*They scored lower on language tests, but according to Jason Malloy this was solely due to the tests not being in their native Pennsylvania Dutch.

Sunday, December 21, 2008

The X chromsome: WTF?   posted by p-ter @ 12/21/2008 12:06:00 PM

The X chromosome in humans is something of an exception with regards to the rest of the genome--as it's diploid only in females, the population genetic forces on it are slightly different. In particular, the effective population size of loci on the X, in a standard neutral model, is 3/4 that of the autosomes. In different demographic models, this fraction can change, so comparing the X to the autosomes is potentially an important tool for understanding human demography.

In a paper published earlier this year, Hammer et al. analysed a data set they had collected of sequences at 40 loci (20 autosomal and 20 on the X) in a number of populations. They saw a striking pattern (the relevant figure from their paper is on the right): in every population they looked at, their estimate of the ratio of effective population sizes on the X and autosomes was greater than 0.75. After additional analyses, they interpreted this as the signature of polygamy in human history.

At the same time, another group (Keinan et al.) was independently looking at this issue in other datasets. Their analysis, published today is markedly different. In particular, they see the exact opposite of the pattern in Hammer et al.--a decrease in the X/autosome ratio in effective population size compared to 0.75 (a figure from their paper is on the right. Note that the y-axis is the same in both this and the Hammer et al. figure--the x/autosome ratio in Ne. In both, the solid horizontal line is at 0.75). . And this is not due to extremely different methodologies--one of the analyses presented by Keinan et al. is very similar to that in Hammer et al., only using different data.

So this is all a bit odd, to say the least.


Saturday, December 20, 2008

The Ghosts of Empires Past   posted by Razib @ 12/20/2008 05:51:00 PM

The blog Strange Maps is candy to a data fiend. I think most readers are aware that I'm one who believes that a thick network of historical & geographic information can be extremely useful in understanding the present; too many people forget that intelligence and ignorance get along just fine. But about a week ago there was a map which leaves you at a loss for words. First a description:
Mr Hecht did some overlay work, and came up with this remarkable fit: "The divide between the (more free-market) PO and the (more populist) PiS almost exactly follows the old border between Imperial Germany and Imperial Russia, as it ran through Poland! How about that for a long-lasting cultural heritage?!?" How about: amazing, bordering on the unbelievable?

Map below the fold (edited for greater clarity).


Transcription around promoters   posted by p-ter @ 12/20/2008 05:38:00 PM

A number of papers out this week (summarized here) notice, using various technologies, the presence of extensive transcription off both DNA strands around active promoters. A figure from one of the papers is above--note the peak in transcription from the sense strand just downstream of the transcription start site (TSS), and the peak in anti-sense transcription just upstream of the TSS. This is an interesting observation, and an example of the unexpected things you can see with new technologies, but no one is exactly sure what to make of it--it could just be the transcriptional machinery being a bit sloppy.

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John Randolph had Klinefelter's syndrome?   posted by Razib @ 12/20/2008 11:37:00 AM

Just a weird historical-genetic note, the radical decentralist Republican John Randolph likely suffered from Klinefelter's syndrome (XXY as opposed to XY). In What Hath God Wrought: The Transformation of America, 1815-1848 the author claims that Randolph's rumored anatomical peculiarities were confirmed postmortem. I only make note of this because it seems strange to me (I don't know why) that the paleoconservative John Randolph Club would be named after a childless eccentric who was likely genetically abnormal. Then again, it also struck me as peculiar that a conservative Christian college based out of Manhattan would name some of its fraternities and sororities after avowed freethinkers.

Friday, December 19, 2008

Nerds on fire?   posted by Razib @ 12/19/2008 01:45:00 AM

Wired has feature, Vote for the Sexiest Geeks of 2008. Jade Raymond seems the most legit on the two dimensions of evaluation.

Thursday, December 18, 2008

Rick Warren & Barack Obama   posted by Razib @ 12/18/2008 09:51:00 PM

Heather Mac Donald, Rick Warren and the Presidency.


Getting people to wash their hands?   posted by Razib @ 12/18/2008 09:26:00 PM

'Gross' Messaging Used To Increases Handwashing, Fight Norovirus:
In fall quarter 2007, researchers posted messages in the bathrooms of two DU undergraduate residence halls. The messages said things like, "Poo on you, wash your hands" or "You just peed, wash your hands," and contained vivid graphics and photos. The messages resulted in increased handwashing among females by 26 percent and among males by 8 percent.

Most human cognition is implicit, and we're really not as amenable to rational appeals we like to think we are. Remember this research?:
We examined the effect of an image of a pair of eyes on contributions to an honesty box used to collect money for drinks in a university coffee room. People paid nearly three times as much for their drinks when eyes were displayed rather than a control image. This finding provides the first evidence from a naturalistic setting of the importance of cues of being watched, and hence reputational concerns, on human cooperative behaviour.


Male & female rotation   posted by Razib @ 12/18/2008 12:20:00 PM

Sex Difference On Spatial Skill Test Linked To Brain Structure:
Men consistently outperform women on spatial tasks, including mental rotation, which is the ability to identify how a 3-D object would appear if rotated in space. Now, a University of Iowa study shows a connection between this sex-linked ability and the structure of the parietal lobe, the brain region that controls this type of skill.

The parietal lobe was already known to differ between men and women, with women's parietal lobes having proportionally thicker cortexes or "grey matter." But this difference was never linked back to actual performance differences on the mental rotation test.

UI researchers found that a thicker cortex in the parietal lobe in women is associated with poorer mental rotation ability, and in a new structural discovery, that the surface area of the parietal lobe is increased in men, compared to women. Moreover, in men, the greater parietal lobe surface area is directly related to better performance on mental rotation tasks.

Wednesday, December 17, 2008

Testing natural selection with genetics   posted by p-ter @ 12/17/2008 09:22:00 PM

H. Allen Orr (one of the authors of the study I mentioned recently) has a fun article in Scientific American on testing hypotheses about natural selection using genetic data. Orr has been one of the few people to try and formally model adaptation in a population genetics framework (I highly recommend this review article from 2005 for a well-written and accessible discussion of this issue), so his thoughts are worth a read.

And if you're in the mood for a chuckle, check out Larry Moran's thoughts on the article.


Tuesday, December 16, 2008

What is that mystery parameter?   posted by Razib @ 12/16/2008 11:38:00 PM

Post-Columbian population movements and the roots of world inequality:
Why should we care about the apparently powerful influence that population origins exert on country and sub-national incomes levels?

First, if this influence is indeed as significant as our findings suggest it to be, then efforts to sort out the roles that geographic, institutional, and other factors play in explaining income levels and growth rates may produce misleading results unless we properly control for it.

Second, the influence of population origins suggests that there is something that human families and communities transmit from generation to generation -- perhaps a form of economic culture, a set of attitudes or beliefs, or informally transmitted capabilities -- that is of at least similar importance to economic success as are more widely recognized factors like quantities of physical capital and even human capital in the narrower sense of formal schooling. If we understand which culturally transmitted factors are important and what contributes to their emergence and propagation, we might be able to design policy interventions that could help less successful groups and countries to close their developmental gaps.

Also, Ancestors and incomes: More on the roots of world inequality. I don't doubt all sorts of implicit cultural norms, information, etc., are transmitted from generation to generation. But there's also something else which is passed from generation to generation which might come to mind....

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Speciation genes   posted by p-ter @ 12/16/2008 05:00:00 PM

RPM points to a couple great papers on the genetics of speciation in Drosophila and mouse. The first is particularly interesting--the gene underlying hybrid incompatibility is also involved in meiotic drive.

What's fun about these sorts of studies is that one can almost start to reconstruct the sequence of population genetic events leading to speciation--like all alleles, one that leads to hybrid infertility has to pass through a phase in which it segregates in the population. This is counterintuitive, of course--any allele causing infertility in some fraction of offspring should be deleterious. One possibility is that divergence at these genes is due to differential selection, and this new paper raises the possibility that sometimes this selection might not be due to external selection pressures, but rather to intragenomic conflict.


The Unread Fisher: Human Evolution   posted by DavidB @ 12/16/2008 04:14:00 AM

The last five chapters of R. A. Fisher's Genetical Theory of Natural Selection - about a third of the book - are devoted to human evolution. These chapters are seldom quoted and probably seldom read, even by Fisher enthusiasts. [Note 1]

There are some obvious reasons for this neglect. Much of this part of Fisher's book is concerned in a broad sense with eugenics, the very mention of which is sufficient to paralyse rational thought in some quarters. But even for those who are not scared of the e-word, there would be reasons for disregarding these chapters. The evidence on which Fisher relies is thin and out-of-date. His evidence on the heritability of human fertility, which is central to his arguments, depends entirely on studies of the British aristocracy, which is hardly a representative sample of the species. Apart from this, like many of his contemporaries (in the 1930s) Fisher believed that current fertility trends were dysgenic: that Britain (and other western nations) were threatened by a decline in the genetic quality of the population. For example, the psychologist R. B. Cattell estimated in 1937 that average IQ in Britain was falling at a rate of about 1 percent per decade. The snag with the dysgenic hypothesis is that the period since the 1930s has seen a large improvement in almost all measurable aspects of human 'quality': IQ, educational achievement, height, general health, and longevity. The average man or woman in Britain today lives about 20 years longer and has an IQ about 20 points higher than in Fisher's day (by 1930 norms). It is possible to argue, like Richard Lynn [Note 2], that an underlying genetic decline has been masked by an even larger environmental improvement, but from a practical point of view pessimists like Fisher and Cattell have been refuted by events.

Nevertheless, there is much in Fisher's neglected chapters which is interesting and worth reading, and this post is intended as a brief taster....

Why Human Evolution is Special

Fisher complains that the treatment of man in general works on evolution is usually superficial, and emphasises that human evolution is interesting and unusual enough to deserve extended treatment. He points out (p.192) that any animal that has undergone profound changes in its recent evolutionary history should be of special interest to the evolutionist. He mentions some of the more obvious special features of man - big brain, exceptional social organisation, use of artificially constructed tools, symbolic communication - and concludes that 'to the non-human observer mankind would present a number of highly interesting evolutionary inquiries and would raise questions not easily to be answered only by the use of comparisons and analogies'(p.192) . But the distinctive perspective he gives to human evolution is that, in contrast to most other species, natural selection in man operates mainly through differences in fertility, rather than mortality, and that it now operates (at least in 'civilized' man) with exceptional intensity (p.218, 228). He goes on to explore the interaction of social class, fertility, and sexual selection, and concludes that the combination of conditions producing an acceleration of evolutionary changes is 'peculiar to man' (p.269). Far from thinking that in modern man evolution has come to a halt, as some modern evolutionists (e.g. S. J. Gould, Steve Jones) have claimed, Fisher therefore believes that it is exceptionally rapid, and capable of producing significant changes even during recorded historical times.

The Evolution of Fertility

Fisher makes some brief but important general remarks on the evolution of fertility, which are applicable to all species, and not just to man. Despite this, his remarks have been generally overlooked. [Note 3] He argues that fertility, like any other trait, is subject to natural selection, and that the most important factor in determining optimal fertility is the amount of parental expenditure required: 'In organisms in which that degree of parental expenditure, which yields the highest proportionate probability of survival, is large compared to the resources available, the optimal fertility will be relatively low' (p.204). In 'civilized' man, the most important determinants of fertility are psychological. There are factors of temperament which determine the propensity to marry, whether marriage is early or late, and the degree of enthusiasm for children (p.210-13). But there are also social and institutional factors such as prohibitions on infanticide (p.218-21). These factors will themselves be affected by psychological influences which will vary over time, (p.219), since parents who are reluctant to commit infanticide will have more children surviving, and the children will tend to inherit their parents' temperament. Fisher argues that this is responsible for the changing historical views on infanticide, and minimises the role of religious doctrine, which itself (he argues) is responsive to the general mood of the population. In a splendidly Fisherian phrase he remarks: 'It would, I believe, be a fundamental mistake to imagine that the moral attitude of any religious community is to any important extent deducible from the intellectual conceptions of their theology (however much preachers make it their business so to deduce it)' (p.222) .

Man versus Social Insects

In several places (p.199-204, 271-2) Fisher compares and contrasts human and insect societies. He stresses the major difference that in insect societies reproduction is specialised in a reproductive caste, often with a single queen. An insect society therefore 'more resembles a single animal body than a human society' (p.200) and 'selection must in this case act exclusively on the reproductive insects via the prosperity of the societies from which they arise' (p.201). In the light of modern sociobiology this emphasis on the reproductive system may seem blindingly obvious, but in Fisher's time it was not, and even in the 1950s writers like A. E. Emerson still tended to neglect it. Fisher also has a most interesting comment on the origins of insect societies, suggesting that 'as soon as the young adults of any incipient social form took either to performing the preparatory labour for reproduction, or to tending the young, before they themselves had commenced to reproduce, the balance of selective advantage would have been shifted towards favouring the fertility of the foundress of the colony, and towards favouring equally the development of the organs and instincts of workers rather than of queens among her earlier, and possibly less well nourished, offspring' (p.205).

In human societies, in contrast, reproduction remains individualistic, and genetic competition within communities is always present. Fisher does not entirely dismiss the importance of inter-group selection: 'Among small independent competing tribes the elimination of tribes containing an undue proportion of the socially incompetent, and their replacement by branches of the more successful tribes, may serve materially to maintain the average standard of competence appropriate to that state of society' (p.201). But even in this state of society competition within the community is present, and becomes more important as the size of groups increases (p.201). He later points out that 'The selection of whole groups is, however, a much slower process than the selection of individuals, and in view of the length of generation in man the evolution of his higher mental faculties, and especially of the self-sacrificing element in his moral nature, would seem to require the action of group selection over an immense period' (p.264. Incidentally, this is the first use of the exact phrase 'group selection' I have noticed in the literature. Sewall Wright, around the same time, uses 'intergroup selection'.) Fisher concludes that the main force in the evolution of such qualities has been individual selection, but powerfully enhanced by the action of kinship groups and sexual selection, which in the case of man also involves decisions by kinship groups. I will discuss this further in another post.

To be continued, probably after Christmas.....

Note 1: I will give page references to the easily available Dover edition (1958). There are no relevant changes from the first edition. Among Fisher's admirers, W. D. Hamilton does in his very first published paper refer to the 'human' chapters of GTNS (see Narrow Roads of Gene Land, vol. 1, p.8), but elsewhere does not, even when (as in his essay 'Innate social aptitudes of man') they would be highly relevant.

Note 2: Lynn has written a book, Dysgenics, and various articles on this theme. He attributes the increase in average IQ (the Flynn Effect) mainly to improved nutrition. The awkwardness of his position is that his argument for dysgenic effects requires the genetic influence on individual IQ to be large, while his interpretation of the increase in IQ also requires the influence of environment to be large - larger in fact than the entire observed Flynn Effect, since this is the net result of a negative genetic trend and a positive environmental effect. This combination of requirements is not logically impossible, but it is uncomfortable.

Note 3: the modern theory of the selection of optimal fertility is usually credited to David Lack, who gathered empirical evidence for it, but the key concept of optimal parental investment is contained not only in Fisher but in various other writers. Fisher himself credited the concept to Major Leonard Darwin.

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Monday, December 15, 2008

Low carb diets and cognitive function   posted by Razib @ 12/15/2008 04:19:00 PM

Low-carbohydrate weight-loss diets. Effects on cognition and mood:
To examine how a low-carbohydrate diet affects cognitive performance, women participated in one of two weight-loss diet regimens. Participants self-selected a low-carbohydrate (n = 9) or a reduced-calorie balanced diet similar to that recommended by the American Dietetic Association (ADA diet) (n = 10). Seventy-two hours before beginning their diets and then 48 h, 1, 2, and 3 weeks after starting, participants completed a battery of cognitive tasks assessing visuospatial memory, vigilance attention, memory span, a food-related paired-associates a food Stroop, and the Profile of Moods Scale (POMS) to assess subjective mood. Results showed that during complete withdrawal of dietary carbohydrate, low-carbohydrate dieters performed worse on memory-based tasks than ADA dieters. These impairments were ameliorated after reintroduction of carbohydrates. Low-carbohydrate dieters reported less confusion (POMS) and responded faster during an attention vigilance task (CPT) than ADA dieters. Hunger ratings did not differ between the two diet conditions. The present data show memory impairments during low-carbohydrate diets at a point when available glycogen stores would be at their lowest. A commonly held explanation based on preoccupation with food would not account for these findings. The results also suggest better vigilance attention and reduced self-reported confusion while on the low-carbohydrate diet, although not tied to a specific time point during the diet. Taken together the results suggest that weight-loss diet regimens differentially impact cognitive behavior.

Also at ScienceDaily. Small N's. What were the N's on the Creatine studies???


Suggested Readings   posted by dkane @ 12/15/2008 01:01:00 PM

Brad Delong reports that Yale professor Chris Blattman is looking for suggested readings for his class "Why is Africa poor and what (if anything) can the West do about it?" Blattman's syllabus (pdf) seems excellent but includes nothing on IQ. What reading(s) would the GNXP crowd suggest he add? I expect that your suggestions will be different from the ones that Professor Blattman has received on his own blog.

The tweakers are crashing on us   posted by John Emerson @ 12/15/2008 07:51:00 AM

Most scientists believe that only objective factors are real and try to eliminate all subjectivity from their explanations -- subjectivity is seen primarily as a source of error. Economists are the most objective social scientists, and they customarily sneer at dumber so-called scientists who fail to reduce human behavior to hard facts.

When things are going well, that is. During times of prosperity economics is a hard science like physics. It's only when things go badly that they kick the can over to psychology and reach for mental factors like "irrational exuberance" and "mental depression" so that they can blame other, stupider sciences for their failures. (Quantum physicists also reach desperately for The Mind at times, since after sixty or seventy years their data are still impossible to interpret.)

So here's my explanation of the present Collapse of Western Civilization: amphetamines. The world of finance is a rather small one, populated entirely by supersmart, extremely aggressive and competitive men (mostly) who have to go at top speed twelve or more hours a day, day after day. How do they do it? Performance-enhancing drugs, that's how: legally-prescribed amphetamines. (Cocaine is uncool, and so Eighties.)

And since finance controls the world, when the tweakers crash, the whole world crashes with them. Like a football team collapsing in the fourth quarter, the world has run out of beans. We've had our jag, and now we're crashing. Not much fun.

In my small experience, amphetamines are very nice. The world becomes a happy place. You get smarter and have lots of energy, and you can keep on going indefinitely. Complex ideas seem simple and all of your ideas look good. The crash isn't even that bad if you use in moderation. But amphetamines are not conducive to moderation.

A friend working in a major science research institute has told me in confidence that a psychologist had told him (also in confidence) that the majority of the researchers there were using amphetamines or something of that kind. Paul Erdos, one of the greatest mathematicians of our time and probably the most prolific, was famous for his reliance on amphetamines. Science magazine has recently suggested that we seriously look into the possibility that the use of amphetamines for performance enhancement should be medically authorized, allowing scientists to do openly what they're already doing under the table.

Erdos always worked with collaborators, and maybe this is the reason for that. While it's working, amphetamine only shows you the bright side of things. It doesn't enhance your judgment, your capacity for self-criticism, or your awareness of problems. Maybe Erdos needed a ground man -- someone to point at his work and say "You know, Paul, I think that you skipped about seventeen steps right there."

The mathematics community is self-policing, but finance absolutely isn't, at least in the short term. A rising tide raises all boats, and when things are going well a clever but foolhardy investor can keep winning for years. Furthermore, someone's who's already persuasive will be even more persuasive while in the grip of amphetamine-induced enthusiasm. Optimists who believe what they're saying are the best con men, and speed gives them the sincere optimism they need. (Have Glassman and Hassett ever been pee tested?)

Negative thinking is necessary and good. The disseminated optimism of crowds is not to be trusted. If we'd had fewer people lighting candles and more people cursing the darkness, we wouldn't be in this fix.

The crash phase of amphetamine psychosis is now before us.

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Do women lighten their hair to compensate for aging?   posted by agnostic @ 12/15/2008 02:17:00 AM

In Jason's post on the distributions of hair and eye color, it looks like women are claiming their hair is lighter than it is. The sex differences are the opposite of what is found when the hair is rated by others. Women are lying because they think it makes them look better.

If they're going to misrepresent their hair color, they're likely to dye it for the same reason. Whether it is to participate in the fashion for blonds in their age cohort or to cater to men in their cohort (there's evidence that younger audiences aren't as captivated by light hair), older women should lighten their hair more. It's like a boob job.

I compared age and hair color data from Playboy Playmates of the Month. I only distinguish between blonds and non-blonds (though there are a few tough calls who I label intermediate). I can't look at age by year since some years have few points. I've grouped the playmates into three ranges: 16 - 20 (n = 210), 21 - 24 (n = 329), and 25 - 35 (n = 105). I chose these groups since each has lots of points. I had to include everyone 25+ in one group, or statistical tests could not have been done.

In any case, these groups also correspond pretty nicely to three phases of a female's reproductive career: 1) the high school or college girl who doesn't have to try at all to look presentable; 2) the early-mid 20-something whose waistline has begun expanding; and 3) the 25+ woman who should have had a child. Here is how the female body shape changes across the lifespan.

So here is a plot of the proportion of each age group that is blond, along with 1 standard error on either side:

The youngest group (where blonds are 42.1%) is statistically significantly different from the oldest group (where blonds are 53.7%), and marginally significantly different from the middle group (where blonds are 48.3%). The middle and oldest groups are not significantly different. (See Appendix for the gory details.)

I conclude that the 16 - 20 year-old playmates had such flawless and tight skin, clear large eyes, gravity-defying breasts and buttocks, etc., that blond hair wouldn't add much. Already by their mid-20s, women's looks have just passed their peak, so that they're probably more likely to dye their hair, although the difference may be illusory. But certainly by 25, the rest of their face and body couldn't compete with those of younger girls, so they begin dying their hair blond to distract the audience from that. (Getting fake boobs would probably show a similar age-related trend.) It's like how restaurants scam the elites by making shitty chicken sandwiches but then tossing on a bit of pesto to make it seem exotic and totally worth $15.

There's another prediction of this idea: if playmates were to be drawn increasingly from older women, they should become blonder too. I've shown that the average playmate has gotten older since a low during most of the 1960s, and in the second link in this post I show that they've also gotten blonder. Indeed, the Spearman rank correlation between a year's average age and average blondness of playmates is +0.35, two-tailed p = 0.006. Taken as a whole, these differences suggest that, even if it isn't as strongly related to aging as is buying moisturizers and skin-firming lotions, lightening the hair is one way that aging women cope with their declining attractiveness.

But if blond hair enhanced attractiveness to the same degree across all ages, then age would not predict the percent of women who dye their hair -- younger girls would do so just as eagerly, as with washing and styling their hair in the morning (a huge boost over a rat's nest). It seems, then, that blondness yields diminishing returns in attractiveness -- I mean, you can't really picture teen star Selena Gomez having to dye her hair. Or for that matter Audrey Hepburn, Jean Shrimpton, Penelope Cruz, or Monica Bellucci bleaching their hair at any age!


I ran an F-test for equality of variances between two samples, one test for each pairwise comparison. None of the three groups had significantly different variances. I then ran a two-proportion z-test (equal variances), one test for each pairwise comparison. The p-values for the tests are: 0.080 (youngest vs. middle), 0.025 (youngest vs. oldest), and 0.164 (middle vs. oldest). These are one-tailed because the prediction was that increasing age should increase the percent who dye their hair or need blond hair to make up for having less attractive skin, breasts, etc. It's like expecting the percent of women with fake boobs and facelift surgery to increase as age increases.

But I made three comparisons, and the more comparisons you make, the more likely you are to find apparently low p-values just by chance. No one really knows how to deal with adjusting the critical p-value (alpha) when you're making multiple comparisons. So rather than futz around with the many theoretical corrections to alpha, I decided to take an empirical attack.

I wrote a program in Python that took all the playmates and separated them into three groups, each one having the same size as the three groups I created based on age. But instead of deterministically using age to sort them, I sampled them at random without replacement to fill the first group, then the second group, with the rest going into the third. Because "group 1," "group 2," and "group 3" were formed randomly, the proportion of blonds shouldn't be too different between them. I performed the same two-proportion z-test (equal variances) as before, one for each pairwise comparison.

I simulated this process 10,000 times, and then took the fraction across all runs that the z-statistic was at least as large as the observed z-statistic, doing so for each of the three group comparisons. These empirical p-values are: 0.0813 (youngest vs. middle), 0.0226 (youngest vs. oldest), and 0.1564 (middle vs. oldest). Therefore, in this case, correcting alpha for multiple comparisons would have been pointless, perhaps because I only made three rather than three thousand comparisons.

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Saturday, December 13, 2008

NLSY blogging: Eye and hair color of Americans   posted by Jason Malloy @ 12/13/2008 09:28:00 PM

So sayeth Aggro in the thread down below:

"They should have measured eye and hair color -- we don't have any representative data! Seriously, they'll take extra long to measure all kinds of weird things that only an anthropometer would know of, but not eye and hair color."

I too have previously lamented this odd failure in easy measurement. A literature search had me coming up short for an adequate published sample of American eye and hair color. The best estimate I could cobble together from several small studies was that about 25% of American whites were blond. But, Ho Ho!, the National Longitudinal Survey of Youth is online and carries these simple treasures within its bosom.

The following hair and eye color information was self-reported in 1985 by a representative sample of those born between 1957-1965 (ages 20-28; currently 43-51). I've included blacks and Hispanics for the gender breakdown:

The first observation is that blond hair is exhibited by a little less than 20% of the white population; smaller than the estimates mentioned above. Second, consistent with Razib's previous look at published data from Iceland and the Netherlands, blue eyes are more common in men than in women. Also like the European data, green eyes are more common in women, though the NLSY difference is not as extreme. Blond hair is also more common in females. The trend in all three groups is for females to report lighter hair pigmentation; 66% of white males report darker hair, compared with 55% of females, and both black and Hispanic females are much more likely than men to report 'brown' hair instead of 'black'. Unfortunately, since the data are self-reported it's difficult to know how much of this is subjective. Is this a further example of lighter pigmentation in women, or does sexual dimorphism in pigmentation lead men and/or women to view their own pigmentation as more "sex-typical"?

I was also curious about how these figures differ for various European-American ancestries:

English ancestry Americans and German Americans are very similar for eye and hair color. Hair color is somewhat darker with the French and Irish, and much darker for Italians. Eye color is not darker for the Irish, but is again somewhat darker for the French, and much darker for the Italians.

Finally, we've also discussed the link between personality, behavior, and light pigmentation before, so I took some quick, rough looks to see if there was any signal within the English/German sample. The answer is: not from what I could see. There were no meaningful differences between dark and light haired people in getting in trouble with the police, in getting into physical fights at school or work, or in pregnancy before marriage.

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Friday, December 12, 2008

Height, weight, waist & BMI of Americans   posted by Razib @ 12/12/2008 09:59:00 PM

Steve has a modestly titled post up, Height and Weight, where he analyzes data from Anthropometric Reference Data for Children and Adults: 2003-2005 (PDF). This is government data on American men, women and children who are Non-Hispanic White, Non-Hispanic Black and Mexican American. I invite readers to peruse the raw data themselves. Steve did a little comparison of various parameters for males and females of the three populations. I thought it would be illustrative to plot the distributions of some the metrics so as to illustrate more intuitively the variation within the populations (the X axis are percentiles). Half Sigma pointed to Steve's post, and the discussion is unsurprisingly vibrant. I think it's safe to assume there is "structure" in something like weight within these populations due to geography and SES. You can see this even in New York City, just start from Bergdorf Goodman (especially around the Holidays) and walk north and east into the Upper East Side. Mean BMI starts dropping. In any case, like Steve I thought focusing on the 20-39 demographic was convenient, in part due to the nature of the readership of this weblog. Here's the CDC's BMI Calculator.

The data I used is here.

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Thursday, December 11, 2008

Making a splash before 40   posted by Razib @ 12/11/2008 04:38:00 PM

Systems biologist, geneticist make notable 'Under 40' lists:
For a fortunate, capable few, life gets rolling sooner. Two of them, Kevin White and Jonathan Pritchard, both 37 and members of the Department of Human Genetics, have been singled out for getting ahead of the numbers.

The Monday, Nov. 3 issue of Crain's Chicago Business named White as one of its "40 Under 40," its annual snapshot of the area's up-and comers. He was the only person on this year's list from an academic setting.

Of course, you haven't hit the big time until you get into Chicago Magazine....

Tuesday, December 09, 2008

GSS blogging   posted by Razib @ 12/09/2008 09:46:00 PM

At Secular Right I stated:
Right now only a few weblogs (that I know of!) seem to make regular recourse to the GSS when confronted with a question amenable to inquiry. The Inductivist, The Audacious Epigone and to a lesser extent Half Sigma. I wish there were more weblogs out there where individuals would take 10 minutes out of their day to double-check their intuitions (on occasion my co-bloggers at GNXP also do GSS data analysis). So with that in mind, if you are inclined to start blogging GSS data, email me at contactgnxp - at - gmail - dot - com. I will add your blog to the blogrolls of both my Gene Expression weblogs, which should give you some Google Pagerank juice. If your posts are topical to the material of Secular Right I would also be inclined to like to you from posts on this weblog.

I'll go further, if a few of these blogs pop up, or come to my attention, I'll do link roundups to try and drive traffic. I might also look into setting up an aggregator site.


A New Yorker in Finland   posted by Razib @ 12/09/2008 11:47:00 AM

Matt Yglesias is in Finland right now, and putting up a series of posts on his observations. I invite any Finnish readers who see him around Helsinki to put their observations in the comments! Perhaps Yglesias should drop in on Jaakkeli's office so he could be schooled on Finnish physics?

Monday, December 08, 2008

Introductions to myself and my interests   posted by DMI @ 12/08/2008 12:14:00 PM

Well, Razib said not to do an intro post, but I figured I should at least say that I'm new 'round these parts, and give a bit of background on my interests.

Everyone knows that evolution is a continuous process, where one population is descended from an ancestral population by a string of intermediates who were capable of interbreeding. Nevertheless, evolution seems to inevitably result in discrete units, which we call species. It would seem that since the beginning, evolution by natural selection was proposed as the causal mechanism being "The Origin of Species". But the general agreement is that Darwin mostly explained the origin of biodiversity, not the origin of species. Part of this problem is that it is incredibly difficult to define a species; we all feel like we can tell when two different populations are species, subspecies, races, or whatever you want, but when it comes down to a hard and fast definition, it is incredibly difficult. This has been the life's work of many biologists and philosophers, including scienceblogger John Wilkins. I'm not going to propose that I know the true definition of a species, but rather that there is one definition that is the most conducive to empirical work regarding species.

That definition is the biological species concept (what, did you think I would suggest anything else?). The BSC was first fully articulated by Ernst Mayr in his classic (but in my opinion somewhat boring) book, Systematics and Origin of Species. The current standard definition is that
species are groups of interbreeding natural populations that are reproductively isolated from other such groups.
This definition shows of precisely why the BSC is a useful definition for research: it tells that if we want to understand the origin of species, we ought to understand the origin of reproductive isolation! This has been the key motivation in the study of speciation for many years now, and is typically broken down into two components.

First of all, there is post-zygotic isolation. This is the kind of reproductive isolation people refer to when they say that horses and donkeys aren't the same species because mules are sterile. However, besides hybrid sterility, there are other forms of post-zygotic isolation, including hybrid inviability and hybrids being less fit. The latter is a particularly interesting case, as we have several interesting (and oftentimes bizarre) stories of hybrids showcasing phenotypes intermediate between the parental phenotypes. An interesting example involves the hybridization of two populations of blackcap with different migratory directions in the lab. The hybrids were actually shown to migrate a direction intermediate to the directions of the parental populations. The fitness consequences should be obvious should this mating be widespread in the the wild.

Pre-zygotic isolation most often refers to pre-mating isolation. For example, various Drosophila species won't mate because they don't understand each others' mating dances. This is relatively easy to understand, but the origin of pre-zygotic isolation was the cause of one of the biggest debates in the history of the study of speciation. One one side, there were those that argued that pre-zygotic isolation would accumulate faster if two incipient species came into secondary contact than it would if they remained allopatric. This idea, called reinforcement, has a satisfying logic to it: if there are fitness consequences for creating hybrids, perhaps there would be selection to minimize the amount of hybrids that are made. Unfortunately, for many years, reinforcement did not seem plausible. That is, until a very important paper was published...

I'll talk about that paper next time (might be a while, though... I'm in the middle of finals right now).

Saturday, December 06, 2008

How different are gene expression levels between Europeans and Africans?   posted by p-ter @ 12/06/2008 08:29:00 AM

In early 2007, a paper on expression differences between populations claimed that something like 25% of all genes are differentially expressed between two population groups (in that case, in cells lines from people of either European or Chinese origin). That paper, though, had a pretty serious flaw--ancestry effect on expression were completely confounded with microarray batch effects, so the precise numbers in the paper were somewhat suspect.

One way to test whether differences between populations in expression levels are real would be to measure expression on admixed individuals--if expression levels correlate with admixure proportions within a sample, that's pretty good evidence that genetic background plays an important role in expression (barring some third factor that correlates with both genetic background and expression of a large number of genes). A population of admixed European-Asian individuals is probably a little hard to come by, but admixed European-African individuals (AKA African-Americans) are less so. A recent paper lays out the results of a study like this in African-Americans.

The results are somewhat surprising--by correlating expression levels with admixture proportions, the authors speculate that nearly all genes have an ancestry effect on expression. The reason this is somewhat surprising is that, given the way the authors did the analysis, it means the expression of a locus depends on a large number of other loci throughout the genome (if the expression levels of a locus were only affected by variation at that same locus, there would be no correlation between total ancestry and expression). Indeed, the authors estimate that only ~12% of heritable variation in expression of a given gene is due to the effects of local (or cis) variation. Other studies have had little success in identifying distant (or trans-acting) effects in humans, this suggests that the reason, as in many other genome-wide association studies, is simply a lack of power.


Human variation proportional to distance from Africa?   posted by Razib @ 12/06/2008 02:34:00 AM

Distance from Africa, not climate, explains within-population phenotypic diversity in humans:
The relative importance of ancient demography and climate in determining worldwide patterns of human within-population phenotypic diversity is still open to debate. Several morphometric traits have been argued to be under selection by climatic factors, but it is unclear whether climate affects the global decline in morphological diversity with increasing geographical distance from sub-Saharan Africa. Using a large database of male and female skull measurements, we apply an explicit framework to quantify the relative role of climate and distance from Africa. We show that distance from sub-Saharan Africa is the sole determinant of human within-population phenotypic diversity, while climate plays no role. By selecting the most informative set of traits, it was possible to explain over half of the worldwide variation in phenotypic diversity. These results mirror those previously obtained for genetic markers and show that 'bones and molecules' are in perfect agreement for humans.

The use of skull-traits is a little 1930s...but a trait is a trait. For you anatomy nerds (of which, I am not one), the list of traits is below the fold. And no, cephalic index is not on the list....
1. Maximum cranial length (GOL)
2. Nasion-opisthocranion (NOL)
3. Cranial base length (BNL)
4. Maximum cranial breadth (XCB)
5. Minimum frontal breadth (M9)
6. Maximum frontal breadth (XFB)
7. Biauricular breadth (M11)
8. Biauricular breadth (AUB)
9. Biasterionic breadth (ASB)
10. Basion –bregma height (BBH)
11. Sagittal frontal arc (M26)
12. Sagittal parietal arc (M27)
13. Sagittal occipital arc (M28)
14. Nasion-bregma chord (FRC)
15. Bregma-lambda chord (PAC)
16. Lambda-opisthion chord (OCC)
17. Basion prosthion length (BPL)
18. Breadth between Frontomalare temporale (M43)
19. Bizygomatic breadth (ZYB)
20. Middle facial breadth (M46)
21. Nasion prosthion height (NPH)
22. Interorbital breadth (DKB)
23. Orbital breadth (M51)
24. Orbital breadth (M51a)
25. Orbital height (OBH)
26. Nasal breadth (NLB)
27. Nasal height (NLH)
28. Nasal height (M55)
29. Palate breadth (MAB)
30. Mastoid height (MDH)
31. Mastoid width (MDB)
32. Breadth between Frontomalare orbitale - Frontal chord (M43(1))
33. Frontal subtense (No 43c)
34. Minimum horizontal breadth of the nasalia (sc) - Simotic chord (M57, WNB)
35. Simotic subtense (No 57a, SIS)
36. Breadth between zygomaxillare anterius - Zygomaxillary chord (M46b, ZMB)
37. Zygomaxillary subtense (No 46c, SSS)


East Asian genetic substructure   posted by Razib @ 12/06/2008 01:58:00 AM

Check out the the charts over at Steve Hsu's site. The author of a forthcoming paper sent him a draft. Since around 2/3 of the population of East Asia resides in China, there would be some value-add in getting many disparate samples from Han groups from all over the country and seeing what the population structure in the nation itself is.

Update: Here's the paper. They do in fact look at geographic structure in China, but it is at a relatively coarse level. Below the fold is a figure which I've reedited a bit for more illustrative power. The plot is across the first two principal components. Unfortunately many of these groups (e.g., Miao, who Americans know as Hmong) are obscure to most, though I'm sure the Xibo's in the readership wil appreciate my labels. Also, remember that a majority of Chinese Americans are from southern dialect groups and regions. The oldest communities are Cantonese, but most of the recent immigrants are from Fujian, and the Taiwanese are over 90% of Fujian origins themselves (the residual being from all over China due to the post-1949 infux).



Wednesday, December 03, 2008

IE issues....   posted by Razib @ 12/03/2008 08:53:00 PM

I'm going to look at the IE issues again. Might even rework the tags underlying the presentation to make things simpler. If you are having a problem with formatting, please tell me what, and the browser (including version) & OS, in the comments.

You = a bloom of fertilizer runoff   posted by p-ter @ 12/03/2008 06:03:00 PM

An interesting paper published today examines the intestinal flora of twins who are either obese or lean in an effort to learn something about the contribution of microbes to human weight. One finding is that obese people tend to have less diverse "microbiomes", and the authors have a fun analogy:
Across all methods, obesity was associated with a significant decrease in the level of diversity. This reduced diversity suggests an analogy: the obese gut microbiota is not like a rainforest or reef, which are adapted to high energy flux and are highly diverse; rather, it may be more like a fertilizer runoff where a reduced-diversity microbial community blooms with abnormal energy input.

Tuesday, December 02, 2008

The 10,000 Year Explosion: How Civilization Accelerated Human Evolution   posted by Razib @ 12/02/2008 11:58:00 AM

5152fXI3EtL._SL500_AA240_.jpgJust wanted to give everyone a heads up, Gregory Cochran's new book, The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, is available for pre-order on Amazon. Of course, I wouldn't trust Amazon's publication date too much....


Monday, December 01, 2008

Widespread copy number variation affecting phenotypes?   posted by p-ter @ 12/01/2008 07:51:00 PM

A report in Science from the annual meeting of the American Society for Human Genetics focuses on copy number variation. Some interesting observations:
Don Conrad and his colleagues at the Sanger Institute have their eyes on smaller common CNVs, as little as 500 base pairs in length. Checking about every 50 base pairs across parts of the genomes of people of African and European ancestry, they uncovered more than 10,000 CNVs--suggesting that other efforts, which have identified about 1500 common ones, are missing most CNVs. Although "there haven't been many" CNVs linked to disease yet, Conrad said in his talk, "there might be quite a few out there." Indeed, he noted that 129 of the 419 genetic-association regions pinpointed in genome-wide association studies hunting for disease DNA contain a common CNV.