Archive for December, 2009

Being black as a state of mind

By Razib Khan | December 22, 2009 2:19 pm

Walter_Francis_White.pngA few days ago I pointed out that actors with visible Asian ancestry, such as Keanu Reeves, Mark-Paul Gosselaar and Dean Cain, can play white characters, while those with visible African ancestry can not (I will leave it to debate whether you think Rashida Jones or Jennifer Beals are violations of that rule or not). On the other hand, it does seem that people with no visible African ancestry can identify as black American due to the norm of hypodescent. For example, consider Walter White, who identified as a black man despite his visible white European appearance. White used his ability to “pass” during his long Civil Rights career since he could operate “undercover.”
One of the unsurprising things which modern genomics is uncovering is that though the median African American has European admixture on the order of ~20%, there is a wide variance. Consider this plot (I’ve reedited it a bit, the figure can be found in this paper) :

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CATEGORIZED UNDER: Culture, Genetics

Less religion = more religious activism?

By Razib Khan | December 22, 2009 3:22 am

Tom Rees:

It seems that when Christianity is popular, Christians are content with the idea of a firewall separating Church and State. It’s only when Christianity begins to lose it’s influence over the population at large that Christians begin to campaign for the State to adopt a Christian character.
Looking at survey data from 18 Western countries, they found:
-The fewer Christians in a country, the greater the support among Christians for a greater public role for religion (as shown in the graph).
-The polarization of views between Christians and non-religious on a public role for religion is greatest in countries where there are fewest Christians.

The relation is illustrated with a nice scatterplot:
Achterberg_2009_truce_cance.png
Some of this can be attributed to specific factors in Europe relating to religious pluralism. Consider my coblogger Martin Rundkvist’s reflections on carolling. Even if a society is very secular, if the dominant religious orientation is uniform, then its background assumptions suffuse one’s daily life. One can therefore be a “cultural” Catholic or Lutheran, with an attachment to the exoteric forms associated with the religion, without being a believer. But when you have religious pluralism thrown into the mix people are going to disagree strenuously about exoteric forms. This applies even to the post-religious; an American atheist from a Jewish background may have a different attitude toward Christmas than an American atheist from a Catholic background. In other words, as European societies have become less Christian over the past generation, they’ve also had to face more religious pluralism. Christians will become more assertive and aggressive in direct response to Europe’s growing Muslim community, which wishes to contest the tacit monopoly that Christianity has long had in Europe as the Faith.
But another issue which might be at work is that as nominal or marginal believers fall away, the set of individuals who remain committed Christians are more religious and exhibit more fidelity to their identity than before. This may result in a group of Christians who are much more cohesive and can engage in collective action out of proportion to their numbers. Whereas before more marginal and nominal members of the community might have served as a check on excessive activism, today those individuals may no longer be part of the Christianity community.
The power of an organized Christian community is clear in a society such as South Korea. Though only around 30% of the population is Christian, with almost half the population not having a religious affiliation at all, Christians have been over-represented in positions of power. The growth of the Christian religion has been rapid, but has slowed over the past 15 years. It seems possible that it may be nearing its “natural limit.” But that does not mean that it won’t influential in the years to come.

CATEGORIZED UNDER: Culture

The fossil record is spotty

By Razib Khan | December 22, 2009 2:07 am

Spatial Organization of Hominin Activities at Gesher Benot Ya’aqov, Israel:

The spatial designation of discrete areas for different activities reflects formalized conceptualization of a living space. The results of spatial analyses of a Middle Pleistocene Acheulian archaeological horizon (about 750,000 years ago) at Gesher Benot Ya’aqov, Israel, indicate that hominins differentiated their activities (stone knapping, tool use, floral and faunal processing and consumption) across space. These were organized in two main areas, including multiple activities around a hearth. The diversity of human activities and the distinctive patterning with which they are organized implies advanced organizational skills of the Gesher Benot Ya’aqov hominins.

ScienceDaily has a summary:

Evidence of sophisticated, human behavior has been discovered by Hebrew University of Jerusalem researchers as early as 750,000 years ago — some half a million years earlier than has previously been estimated by archaeologists.
The discovery was made in the course of excavations at the prehistoric Gesher Benot Ya’aqov site, located along the Dead Sea rift in the southern Hula Valley of northern Israel, by a team from the Hebrew University Institute of Archaeology. Analysis of the spatial distribution of the findings there reveals a pattern of specific areas in which various activities were carried out. This kind of designation indicates a formalized conceptualization of living space, requiring social organization and communication between group members. Such organizational skills are thought to be unique to modern humans.
Attempts until now to trace the origins of such behavior at various prehistoric sites in the world have concentrated on spatial analyses of Middle Paleolithic sites, where activity areas, particularly those associated with hearths, have been found dating back only to some 250,000 years ago.
The new Hebrew University study, a report on which is published in Science magazine, describes an Acheulian (an early stone tools culture) layer at Gesher Benot Ya’aqov that has been dated to about 750,000 years ago. The evidence found there consists of numerous stone tools, animal bones and a rich collection of botanical remains.

500,000 years! This could be wrong, who knows? My network of priors in this area is too thin to evaluate the probability (leave it to someone like John Hawks). Rather, it is important to remember that the fossil record gets really thin the further back you go. Hominins were never common to begin with, at least before the recent past. There’s a huge fossil gap in China for example between the early Homo erectus and the Holocene. I bring this up because John Horgan has been arguing that there’s no evidence for “war” before the rise of agriculture, based on Brian Ferguson’s research. Part of the issue might be how you define war. But another issue might be that this is a case where the sample sizes over time are small enough that you might actually miss a lot.
Citation: Nira Alperson-Afil, Gonen Sharon, Mordechai Kislev, Yoel Melamed, Irit Zohar, Shosh Ashkenazi, Rivka Rabinovich, Rebecca Biton, Ella Werker, Gideon Hartman, Craig Feibel, and Naama Goren-Inbar, patial Organization of Hominin Activities at Gesher Benot Ya’aqov, Israel, (18 December 2009), Science 326 (5960), 1677. [DOI: 10.1126/science.1180695]

CATEGORIZED UNDER: Anthroplogy

Louisiana should be the happiest and New York the least

By Razib Khan | December 21, 2009 5:02 am

Objective Confirmation of Subjective Measures of Human Well-Being: Evidence from the U.S.A.:

A huge research literature, across the behavioral and social sciences, uses information on individuals’ subjective well-being. These are responses to questions–asked by survey interviewers or medical personnel–such as “how happy do you feel on a scale from 1 to 4?” Yet there is little scientific evidence that such data are meaningful. This study examines a 2005-2008 Behavioral Risk Factor Surveillance System random sample of 1.3 million United States citizens. Life-satisfaction in each U.S. state is measured. Across America, people’s answers trace out the same pattern of quality of life as previously estimated, using solely nonsubjective data, in a literature from economics (so-called “compensating differentials” neoclassical theory due originally to Adam Smith). There is a state-by-state match (r = 0.6, P < 0.001) between subjective and objective well-being. This result has some potential to help to unify disciplines.

Basically they constructed an index of quality of life based on objective metrics. They then compared how those metrics related to surveyed subjective happiness, and came up with this 50 state scatterplot:
happiness.png
The correlation being ~0.6, that means that 36% of the variation of of subjective assessments of life satisfaction can be predicted by the variation in on the presumed predictors of happiness. Note that underlying demographic variables are controlled here. As I said above, Louisiana is ranked so that it should be the happiest state while New York the least. Here’s the full list of 50 states:

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CATEGORIZED UNDER: Culture

Avatar

By Razib Khan | December 20, 2009 4:25 am

I saw Avatar in 3D.
- The special effects were very good. I have seen special effects of similar quality, but never such quality in such quantity. The detail was striking enough that I assume I stopped thinking of it as “special effects” and more as simply a background canvas. I’m talking more about the landscape, the flora and fauna, than the humanoids, who occasionally slipped into uncanny valley territory.
- The plot was melodramatic and not particularly exceptional. The ideological ax didn’t bother me because the plot was mostly extraneous to the film’s experience anyhow.
- I think that the 3D was really not much of a value-add. It was often distracting, especially at the beginning.
I don’t know how well this film will do. But I think it’s right to assume that this sets a new standard in terms of special effects. In many films special effects are most evident and utilized in action sequences or in alien contexts, when there’s a lot of sensory overload and you can’t fixate too much on whether they look fake or not. In Avatar an entire ecology was constructed, and there were many moments of idyllic calm when one could focus on the detail.
Note: The were many sequences which gave me flashbacks to 2005′s The New World.

CATEGORIZED UNDER: Culture

Katz

By Razib Khan | December 18, 2009 2:22 pm

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CATEGORIZED UNDER: Blog

The myopia epidemic!

By Razib Khan | December 17, 2009 10:10 pm

Increased Prevalence of Myopia in the United States Between 1971-1972 and 1999-2004:

Results
Using the 1971-1972 method, the estimated prevalence of myopia in persons aged 12 to 54 years was significantly higher in 1999-2004 than in 1971-1972 (41.6% vs 25.0%, respectively; P < .001). Prevalence estimates were higher in 1999-2004 than in 1971-1972 for black individuals (33.5% vs 13.0%, respectively; P < .001) and white individuals (43.0% vs 26.3%, respectively; P -2.0 diopters [D]: 17.5% vs 13.4%, respectively [P -7.9 D: 22.4% vs 11.4%, respectively [P < .001]; -7.9 D: 1.6% vs 0.2%, respectively [P < .001]).
Conclusions
When using similar methods for each period, the prevalence of myopia in the United States appears to be substantially higher in 1999-2004 than 30 years earlier. Identifying modifiable risk factors for myopia could lead to the development of cost-effective interventional strategies.

Here are some tables:

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CATEGORIZED UNDER: Health, Medicine

Wired for justice?

By Razib Khan | December 17, 2009 9:52 pm

Since my last post was rather pessimistic, I thought I’d point to something a little more cheerful, Social Scientists Build Case for ‘Survival of the Kindest’:

Researchers at the University of California, Berkeley, are challenging long-held beliefs that human beings are wired to be selfish. In a wide range of studies, social scientists are amassing a growing body of evidence to show we are evolving to become more compassionate and collaborative in our quest to survive and thrive.
In contrast to “every man for himself” interpretations of Charles Darwin’s theory of evolution by natural selection, Dacher Keltner, a UC Berkeley psychologist and author of “Born to be Good: The Science of a Meaningful Life,” and his fellow social scientists are building the case that humans are successful as a species precisely because of our nurturing, altruistic and compassionate traits.
They call it “survival of the kindest.”
“Because of our very vulnerable offspring, the fundamental task for human survival and gene replication is to take care of others,” said Keltner, co-director of UC Berkeley’s Greater Good Science Center. “Human beings have survived as a species because we have evolved the capacities to care for those in need and to cooperate. As Darwin long ago surmised, sympathy is our strongest instinct.”

Human nature is mixed. There’s a bit of Jekyll and Hyde in everyone, and likely to variant extents as well. But empirically we know that human competencies are such that we can scale social organizations to an incredibly complex level. In fact I think evolutionary anthropologists have established with a high degree of certainty that the Hobbesian model of “all against all” is not grounded in the natural history of our species. Rather, we have been a rather groupish lineage for a long time, and recently we have been scaling up the size and complexity of our groups quite a bit.

CATEGORIZED UNDER: Evolution, Psychology

Doing the right thing, doing the legal thing

By Razib Khan | December 17, 2009 9:02 pm

Megan McArdle has a post up where she follows up on her disgust with home owners who “walk away” from their mortgage obligations when they can continue to pay them. In California, and many other states, the bank can’t come after you if you walk away, so if your home is “underwater” then it is often a “rational” decision.
Megan makes the point that our economic and social system does not rely purely on rational self-interest, but also on an accumulated capital of norms which lead to virtuous cycles. My family is from Bangladesh, and I have seen this first hand. Corruption & nepotism in Bangladesh are almost impossible to change because it is stuck in an equilibrium state; if you are the first person to not be corrupt or nepotistic you’re only causing hardship to your family and relatives while others prosper. As an example, I have an uncle who works as a civil servant and has been promoted to a relatively high position because he is known to be someone who refuses to take bribes. The reason my uncle does not take bribes is mostly due to family tradition,* and, I suspect some personality quirks inherited from one of my grandfathers (he was a notoriously guileless individual, and that tendency has passed on to some of his children). Though his clean reputation means that he is in high esteem in the eyes of his colleagues, it is also a running joke that all of his subordinates live in palatial homes while he has a modest apartment! This causes some awkwardness because he simply can not entertain any of his subordinates since his material condition is so inferior to what they are accustomed to. In terms of innate moral character I doubt my uncle is elevated in any particular way from his colleagues and subordinates. Rather, he has an idiosyncratic and plainly irrational set of norms when it comes to maximizing his material wealth.**

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CATEGORIZED UNDER: Anthroplogy, Culture, Economics

How Argentina became white

By Razib Khan | December 17, 2009 1:42 pm

Apropos of my skepticism of Census projections of 2050 demographic balances, there’s a new paper out on Argentina which is relevant. Here’s Wikipedia on Argentina’s self-conception:

As with other areas of new settlement such as Canada, Australia and the United States, Argentina is considered a country of immigrants. Most Argentines are descended from colonial-era settlers and of the 19th and 20th century immigrants from Europe, and 86.4% of Argentina’s population self-identify as European descent. An estimated 8% of the population is mestizo, and a further 4% of Argentines were of Arab or East Asian heritage. In the last national census, based on self-identification, 600,000 Argentines (1.6%) declared to be Amerindians (see Demographics of Argentina for genetic studies on the matter). Following the arrival of the initial Spanish colonists, over 6.2 million Europeans emigrated to Argentina from the mid-19th to mid-20th centuries Argentina was second only to the United States in the number of European immigrants received, and at the time, the national population doubled every two decades mostly as a result.

In contrast to Mexico, which is self-consciously a synthetically a “mestizo” nation which conceives of itself as a cultural and biological synthesis between European and native, I think it is fair to portray Argentineans as a settler society of Europeans in their self-image. As I have said before, this mythos goes a bit too far. The median Argentinean probably has enough indigenous ancestry to qualify as a Native American tribal member in the United States by the rules of blood quantum (on the order of 20-25%). Here’s a multi-dimensional genomic window into this reality, Inferring Continental Ancestry of Argentineans from Autosomal, Y-Chromosomal and Mitochondrial DNA:

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CATEGORIZED UNDER: Anthroplogy, Genetics

On linear projections

By Razib Khan | December 17, 2009 2:18 am

White Americans’ majority to end by mid-century:

The estimated time when whites will no longer make up the majority of Americans has been pushed back eight years — to 2050 — because the recession and stricter immigration policies have slowed the flow of foreigners into the U.S.
Census Bureau projections released Wednesday update last year’s prediction that white children would become a minority in 2023 and the overall white population would follow in 2042. The earlier estimate did not take into account a drop in the number of people moving into the U.S. because of the economic crisis and the immigration policies imposed after the Sept. 11, 2001, terror attacks.
The United States has 308 million people today; two-thirds are non-Hispanic whites.

First, the title is a little of a misnomer. In the 2000 Census 47% of Hispanics identified as whites (42% as “other,” with the balance blacks, mixed, Asian, etc.).* But the reality is that under the American law for operational purposes (e.g., affirmative action) there’s no distinction between white and non-white Hispanics (though socially no doubt white Hispanics experience life differently than Hispanics of black, indigenous or mixed origin). But the bigger point is the problems and sensitivities to initial conditions when it comes to straight line projections. You never know what’s going to happen. I just read today in a book published this year that St. George’s, Utah, will have a population of 450,000 in the year 2030! This is ridiculous. In any case, I took Census projections and plotted the one which posits a middling level of immigration.

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CATEGORIZED UNDER: Culture

Are Chinese subsets of Southeast Asians?

By Razib Khan | December 15, 2009 7:23 am

That’s probably the big takeaway of a new paper on the genetics of Asians, a set which includes South Asians, but in the new research mostly focuses on the people of East Asia. In a global context this work is important. The backstory is that there are disagreements about the exact process of the “Out of Africa” migration. Most researchers would agree that the vast majority, perhaps all, of the distinctive genetic content of the human species derives from a migration from the African continent between 50 and 100 thousand years ago (closer to the former date than the latter likely). Note that there were other human lineages outside of Africa, the Neandertals being the most prominent, but various “archaic” groups were extant in eastern Asia as well down to the arrival of modern African-derived human groups. This is part of the reason why H. floresiensis isn’t that outlandish, a lineage of H. er ectus was extant in Southeast Asia until the ~50,000 years ago, with the arrival of moderns.
Those are the agreements. The disagreement, in particular in regards to East Asia, is rather simple. Was there one, or two, waves from Africa, and did one, or both, settle East Asia? The two-wave model was promoted heavily in the early aughts by Spencer Wells. The whole argument is laid out in his book The Journey of Man: A Genetic Odyssey. The title hints to the fact that Wells and his collaborators primarily focused on paternal lineages, the Y chromosomes, in their reconstructions. Here’s a screenshot from The Genographic Project which highlights the two-wave model:
genographc.png
In the context of East Asia, the two-wave model posits that there was a southern coastal migration, which pushed into Australia via southern India. And, there was a northern migration up through Central Asia from which arose both Europeans and East Asians.
The new paper in Science is Mapping Human Genetic Diversity in Asia:

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CATEGORIZED UNDER: Anthroplogy, Genetics

I for one welcome our future cephalopod overlords!

By Razib Khan | December 15, 2009 5:13 am

octpus.pngCool new report in Current Biology, Defensive tool use in a coconut-carrying octopus:

The use of tools has become a benchmark for cognitive sophistication. Originally regarded as a defining feature of our species, tool-use behaviours have subsequently been revealed in other primates and a growing spectrum of mammals and birds…Among invertebrates, however, the acquisition of items that are deployed later has not previously been reported. We repeatedly observed soft-sediment dwelling octopuses carrying around coconut shell halves, assembling them as a shelter only when needed. Whilst being carried, the shells offer no protection and place a requirement on the carrier to use a novel and cumbersome form of locomotion — ‘stilt-walking’.

No surprise that when we are looking to a violation of an old “human exceptional” character (though tool-use seems to have been violated a fair amount now by any interpretation) that the cephalopod would step up to the plate. I’ve heard of weird behavior by octopuses in laboratories which begs to be anthropomorphized, but no one denies that this is one taxa which has some brains. Who says you need a notochord to be a “higher animal”? Anyone who’s read a fair amount of science fiction also is aware that cephalopods are one of the more exotic, but still frequent, candidate earth lineages which might potentially rise to sapience. Fore all the aquatic species who have the glimmer of intelligence cybernetics might offer up some potential avenues of freedom and leveling the playing field with the terrestrials.
Citation: Defensive tool use in a coconut-carrying octopus, Finn, Julian K.; Tregenza, Tom; Norman, Mark D. doi:10.1016/j.cub.2009.10.052 (volume 19 issue 23 pp.R1069 – R1070)

CATEGORIZED UNDER: Ecology

SAD in Google Trends

By Razib Khan | December 13, 2009 11:27 pm

I was looking for the term “Depression,” in the economic sense. But look at the clear seasonal trend in search for the term:
depressionchart.png

CATEGORIZED UNDER: Economics

Katz

By Razib Khan | December 11, 2009 2:38 am

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CATEGORIZED UNDER: Blog, Culture

Who believes in the evil eye?

By Razib Khan | December 10, 2009 3:59 pm

A friend pointed me to a new Pew survey, Many Americans Not Dogmatic About Religion. It shows the general finding that though Americans are a religious people, they’re moderately ecumenical in their practices and beliefs. I was concerned in particular though with the resurgence of supernatural beliefs with the decline of institutional religious orthodoxy.
The back story to this is that many psychologists posit that humans have an innate predisposition toward supernatural beliefs because of the cognitive biases we’re hardwired with. For example, it isn’t a coincidence that almost all human societies seem to have the idea of what we would term ghosts, or that systematic astrology arose independent several times. Naive intuitions about mind-body duality or inferences one might make from the repetitive action of the stars against the cosmos are evoked by our common hardwire.
Organized “higher religion” changed this somewhat, channeling and leveraging some intuitions (the afterlife, gods, etc.), but marginalizing others (ghosts, demigods, etc.). In particular, there has always been a tension between the relatively narrow set of beliefs acceptable to religious professionals and the elites, and the more general and diverse array of superstitions in circulation among the populace. Religious “reform” movements often aim at extirpating folk religion whose general outlines seem culturally universal; e.g., relics, veneration of local saints and demigods, and traditional fertility festivals. This was evident in both the Protestant and Catholic Reformation, and also among Muslim and Hindu fundamentalists, who attempt to strip out what they perceive to be exogenous accretions to the “true religion.”
With the decline in institutional religion in the West one would predict folk beliefs to reemerge, as the control of mass belief by the elites is no longer enforced by the state or higher institutions. The Pew survey seem to point a bit to this, there is a general trade-off in religious orthodoxy and attendance and belief in supernatural concepts which are outside the purview of Western Christianity. Below the fold I’ve shown the pairwise absolute and relative differences between categories in terms of their acceptance of various non-orthodox supernatural concepts.

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CATEGORIZED UNDER: Culture, Religion

Ashkenazi Jews are Middle Eastern & European hybrids

By Razib Khan | December 9, 2009 5:20 pm

According to search engine traffic one of the most popular posts on this weblog has to do with the genetic background of Ashkenazi Jews. That is, those Jews whose ancestors derive from Central & Eastern Europe, and the overwhelming number of Jews in the United States. The genetic origins of this group are fraught with politics naturally. With the rise of biological science the characteristics of Jews were used as a way to differentiate them as a nation apart in more than a cultural and religious sense. After World War II other researchers attempted to show that Jews were not genetically distinct with relatively primitive blood group assays. Rather, they were the descendants of converts.
More recent genetic work has given mixed results. The reasonable inference then is that Jews themselves are a population with a complex history, and that complexity is manifest in their genetics. A new paper explores these issue in more detail, Genomic microsatellites identify shared Jewish ancestry intermediate between Middle Eastern and European populations:

Background
Genetic studies have often produced conflicting results on the question of whether distant Jewish populations in different geographic locations share greater genetic similarity to each other or instead, to nearby non-Jewish populations. We perform a genome-wide population-genetic study of Jewish populations, analyzing 678 autosomal microsatellite loci in 78 individuals from four Jewish groups together with similar data on 321 individuals from 12 non-Jewish Middle Eastern and European populations.
Results
We find that the Jewish populations show a high level of genetic similarity to each other, clustering together in several types of analysis of population structure. Further, Bayesian clustering, neighbor-joining trees, and multidimensional scaling place the Jewish populations as intermediate between the non-Jewish Middle Eastern and European populations.
Conclusion
These results support the view that the Jewish populations largely share a common Middle Eastern ancestry and that over their history they have undergone varying degrees of admixture with non-Jewish populations of European descent.

The general results of the paper are well illustrated by the figures.

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CATEGORIZED UNDER: Culture, Genetics

Why homes aren't investments, not enough people think they are

By Razib Khan | December 9, 2009 3:46 pm

At Reuters Felix Salmon has been making the case that a home should not be thought of as an investment. Here’s the the Google Trends for “investment property”:
investmentproperty.png
I think the biggest argument that one should be careful about viewing a home purchase as an investment is that many people will now roll their eyes at you when you moot the idea. In other words, a substantial proportion of young adults are going to view the idea of getting locked down into a mortgage with a great deal more skepticism than they would have a few years ago. The cultural shock of the late real estate correction is going to have a significant long term effect on demand for homes. It seems that the real estate bubble was driven in part by a positive feedback loop whereby as homes became more valuable due to increased demand, the demand itself began to rise as more & more wanted to “get in” on a “sure thing.” Without the expectation of inevitably rising values I suspect that many potential buyers will simply focus on more liquid investment opportunities.

CATEGORIZED UNDER: Culture

"Americans" don't like Barack Hussein Obama

By Razib Khan | December 8, 2009 6:40 pm

I post some data analysis over at my other weblog. For example, today I looked at the relationship between food stamp usage and unemployment. The Census makes a lot of county-level data available, though it’s often slapdash and disorganized. But using R I’ve constructed many data sets including most American counties. I don’t post here much because I concentrate more on science in this space, and the 500 pixel width means that integrating scatter plots into a post seamlessly is pretty much impossible.
But since readers of this weblog are much more liberal than over at GNXP Classic, I thought you’d be interested in what demographic variables predict voting for Barack Obama on the county-level. So the dependent variable is the 2008 results for Barack Obama by county.
The independent variables are:
% of non-Hispanic whites who identify German
% of non-Hispanic whites who identify as “American”
% black
% Median household income
% Median home value
% with a college degree
% on food stamps
% obese
Below are the coefficients with errors and p-values if not significant).

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CATEGORIZED UNDER: Culture, Politics

The downside of beauty

By Razib Khan | December 8, 2009 5:30 am

250px-Triumph_of_Achilles_in_Corfu_Achilleion.jpgWell, I don’t quite know about that, but that’s the sort of take-away from a new paper in PLoS Biology which looks at the downsides of female attractiveness. A Cost of Sexual Attractiveness to High-Fitness Females:

Adaptive mate choice by females is an important component of sexual selection in many species. The evolutionary consequences of male mate preferences, however, have received relatively little study, especially in the context of sexual conflict, where males often harm their mates. Here, we describe a new and counterintuitive cost of sexual selection in species with both male mate preference and sexual conflict via antagonistic male persistence: male mate choice for high-fecundity females leads to a diminished rate of adaptive evolution by reducing the advantage to females of expressing beneficial genetic variation. We then use a Drosophila melanogaster model system to experimentally test the key prediction of this theoretical cost: that antagonistic male persistence is directed toward, and harms, intrinsically higher-fitness females more than it does intrinsically lower-fitness females. This asymmetry in male persistence causes the tails of the population’s fitness distribution to regress towards the mean, thereby reducing the efficacy of natural selection. We conclude that adaptive male mate choice can lead to an important, yet unappreciated, cost of sex and sexual selection.

The dynamic is well illustrated by the first figure:
journal.pbio.1000254.g001.png
The two lines above the shaded distribution illustrate variant male preference strategies. The solid lines shows random preference for females as a function of size, while the dashed line shows biased preference toward larger fitter females. The two lines below show the distribution of female fitness in response. In the case of the solid line you see the fitness of females in the context of random preferences; that is, males do not strongly prefer females who are fecund because of their large size. The reason that a large female may be more fecund is rather obvious, more physiological resources expendable upon the offspring. The evolutionary anthropologist Sarah Blaffer Hrdy claims the same principle is operative among humans in her book Mother Nature, larger females are less likely to miscarry and have complications, and can provide more robustly for their young. If one is healthy enough to construct a large and robust physique, one normally does so.
And yet as you can see above, strong male preference for these fecund females reduces their fitness. Male persistence from what I can tell might be colloquially termed “harassment.” The energetic surfeit which larger females might allocate to their own reproductive output for provisioning has to be expended upon fending off males. In a context where males strongly prefer large females their fitness advantage is actually mitigated! This is a really weird outcome of sexual preferences.
The model rests on four primary assumptions:

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CATEGORIZED UNDER: Evolution, Genetics
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