Heritability of voting

Genetic Variation in Political Participation:

The decision to vote has puzzled scholars for decades…The results show that a significant proportion of the variation in voting turnout can be accounted for by genes. We also replicate these results with data from the National Longitudinal Study of Adolescent Health and show that they extend to a broad class of acts of political participation. These are the first findings to suggest that humans exhibit genetic variation in their tendency to participate in political activities.

Additive genetic variance ~ 0.50. You can read the whole paper, though I’ve blogged it elsewhere.

Pigmentation loci, TPCN2 and ASIP

Sandy pointed me to letter to Nature by a group which has done some earlier pigmentation work, Two newly identified genetic determinants of pigmentation in Europeans:

We present results from a genome-wide association study for variants associated with human pigmentation characteristics among 5,130 Icelanders, with follow-up analyses in 2,116 Icelanders and 1,214 Dutch individuals. Two coding variants in TPCN2 are associated with hair color, and a variant at the ASIP locus shows strong association with skin sensitivity to sun, freckling and red hair, phenotypic characteristics similar to those affected by well-known mutations in MC1R.

All well and good, but do note that in the fine print that it is the odds ratio for OCA2 really jumps out at you.
Related: SLC24A5, SLC45A2, TYRP1, OCA2 and KITLG.

In Our Time, The Arab Conquests

On this week’s In Our Time they’re talking about the Islamic conquests. The author of When Baghdad Ruled and The Great Arab Conquests is one of the guests, so if you meant to read the books but never got around to it for whatever reason, might be worth a listen. As I told a friend the first few centuries of the emergence of what we know as the Islamic World (650-850) are interesting, but after that point you hit a somewhat stationary state (most of the sects and schools of Islamic law emerged during this period, even if their identity only full crystallized between 850 and 1150). Details such as how Iran was transformed into a Shia state by the Safavids in the 16th century are not trivial, but they pale in contrast to the implications for world history of a new ideology & empire which stretched from the Atlantic to the Indus.

Why “Asian” mice have straight hair

Humans, being who we are, are really interested in how our external phenotype is shaped. Since the year 2000 many of the genetic underpinnings of the gross physical features which we use to categorize people, the sort of thing that might show up in a people description, have been elucidated. We know, for example, the genes which control variation in skin color to a first approximation at this point. It also seems that we’ve zeroed in on the primary gene responsible for eye color variation. Additionally, recently there’s been the discovery of the gene which seems to control East Asian hair form, EDAR. At my other weblog p-ter posts on a new paper, Enhanced ectodysplasin-A receptor (EDAR) signaling alters multiple fiber characteristics to produce the East Asian hair form. Go there for the summary and awesome picture of the “Asian” mice.

EDAR again

There have been a number of posts on this site regarding EDAR–in summary, a non-synonymous SNP has swept up to high frequency in East Asian populations via positive selection, and appears to account for some variation in hair form. The evidence for function in hair form comes largely from an association study on hair thickness. Now add a mouse model to the evidence:

We show that elevation of Edar activity in transgenic mice converts their hair phenotype to the typical East Asian morphology. The coat texture becomes coarse, with straightening and thickening of individual hairs and conversion of fiber cross-sectional profile to a circular form. These thick hair fibers are produced by enlarged hair follicles, which in turn develop from enlarged embryonic organ primordia. This work shows that the multiple differences in hair form between East Asian and other human populations can be explained by the simplest of genetic alterations.

On the right is a wild-type mouse, contrasted with the “Asian” mouse. The mechanism by which this works is kind of intriguing–apparently the substitution in EDAR leads to increased signaling via NFkB, but it’s an open question (both in this case and more generally) how the modification of the activity of a transcription factor leads to phenotypic changes at the level of an organism.

Selection, drift, disease and complexity, all rolled into one….

One of the great things about evolutionary genetics is that it is such a diverse field in terms of the cognitive toolkit which one must access as a matter of course. Since R. A. Fisher’s The Genetical Theory of Natural Selection (along with the contemporaneous work of Sewall Wright and J. B. S. Haldane) we’ve been habituated toward thinking of evolutionary processes on an abstract level which might allow us to make general deductive inferences from first principles. Genetic drift, selection, migration, etc., are parameters which are used to construct models that allow us to generate predictions and obtain deeper insight. The discovery of DNA and the elucidation of the biophysical substrate which constrains the modes of inheritance in a concrete manner opened up the startling vistas of molecular evolutionary genetics. This discipline has allowed an inspection of how the predictions of evolutionary theory are born out on a more fine grained level. And today the genomics revolution is ramping up the data sets as computational power enables more powerful extraction of the patterns and dynamics which emerge out of these discrete streams of information.
But this is all rather philosophical and abstract. Yesterday I posted on a paper which showed how selection and drift might have operated upon the frequency of an allele which has a disease implication, and so has a pragmatic impact on quality of life. Today I’d like to bring your attention to another paper which synthesizes the big picture ideas which might entail consequences in terms of the utilitarian details of daily life, Natural Selection on Genes that Underlie Human Disease Susceptibility:

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Postgrad education vs. literalism: update

Last month my posts Biblical literalism or low IQ: which came first? and Educational levels & denomination got a lot of play around the blogosphere. I used the US Religious Landscape Survey to get demographic data for denominations, but I had to cobble together numbers on Biblical literalism, etc. But with a further release of data I can now flesh out almost all the denominations plotting postgrad education % vs. belief that the Bible is the literal word of god.
Clarification: Y axis = % with postgrad education. X axis = % who believe the Bible is the literal word of god.
postgradvswordsmall.jpg
As you can see, the trend still holds with more denominations. I decided to do this since people were curious about denomination X, and I didn’t have that included. Click the image or here for a larger version so you can see the labels. And here is a chart with all religious affiliations included (e.g., includes non-orthodox Christians such as Mormons as well as non-Christians). Below the fold I’ve put the raw data I used, but if you want to snatch it for yourself, here it is as a CSV file (if you do some statistical analysis of the data post a link in the comments and I’ll link next week).

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Your generation was more violent

Previously we found that your generation was sluttier, so we turn now to another great threat to civilization — violence (between individuals). As before, our concern is with whether violent crime rates are increasing or decreasing, and not so much with the absolute level: it is easier to screw up civilization than it is to improve on it, so a decline can quickly snowball, while it may take much longer to restore things to their previous levels.

There are very good and very clear data on violent crime, so this post will be much more direct than the one on sluttiness. Let’s begin with homicide. The Bureau of Justice Statistics, part of the US Department of Justice, has taken homicide data from the CDC’s National Center for Health Statistics and put it into a straightforward graph. I see five trends in the graph: an increase from 1900 to the mid-1930s, a decrease from the mid-1930s to about 1960, an increase from 1960 to the late 1970s, a fairly steady high level (with oscillations) throughout the 1980s, and a decrease from 1992 to the present.

To be generous to older generations, let’s say that much of this homicide is committed by 15 year-olds. That means that the cohort born in 1945 is responsible for the increase that began in 1960. I figure you have to be about 73 years old in order to decry how violent the younger generations have been — certainly the Boomers and Gen X-ers cannot complain, while Generation Y should be thankful they’ve lived through such peaceful times.

The homicide data also caution against viewing the past with rosy spectacles — there was nothing peaceful at all about the first third of the 20th century. Declinists who long for better times in the past seem to latch onto a fleeting period of rest and prosperity. That’s fine, as far as worshipping one period over another goes. However, we should not think that we can easily maintain that level, whether through individual choice or institutional incentives, as oscillations and limit cycles appear to be the rule rather than the exception. We should aim instead to have a somewhat low level of Bad Things, with low-amplitude fluctuations, and not let the mere existence of waxing and waning cause us hysteria.

What about the intersection of sex and violence — how have forcible rape rates changed over time? Again we turn to BJS data, although they do not go back nearly as far as homicide data, the earliest year being 1960. After retrieving data from this page, looking at the entire United States, forcible rape rate, from 1960 to 2006, I put them into a simple graph:

There are only two trends here: an increase from 1963 to 1992, and a decrease afterward. In fact, the two trends look pretty linear on first glance. The slope of the increasing trend is about +1.11, and the slope of the decreasing trend is about -0.85, confirming the hunch that the decline of civilization snowballs more quickly than its restoration proceeds. As with homicide, Boomers and Gen X-ers cannot complain about rape epidemics in recent generations. This is particularly true for the Boomers and Gen X-ers who manufactured and continue to prop up the myth of the campus rape crisis.

The BJS also has an index of “violent crime” that includes murder and non-negligent manslaughter, forcible rape, robbery, and aggravated assault. I used the same search function as for the rape rate graph, and the trends for this general violent crime rate look the same as the rape rate trends, so I won’t include the graph. In brief, there’s an increase from 1962 to 1991, and a decrease afterward.

As in the case of sluttiness, using popular culture as a means of taking civilization’s pulse is highly unreliable. Before, we saw that slutty behavior has been decreasing even as perceived slutty appearances have been increasing. Here, we see that violent crime has been decreasing even as video games, movies, and TV shows have become increasingly violent. To pick just one example, gangsta rap was invisible during the 1980s and only became popular when Dr. Dre’s album The Chronic came out in 1992, drawing ever larger audiences throughout the 1990s — at the very time when violent crime was falling.

I don’t believe that trends in real behavior and in popular culture are causally related in an inverse way either — just that they are independent of each other. Cycles of fashion in the cultural realm are self-contained, and oscillations and limit cycles in real behavior are also self-contained, at least to a first approximation. I’ve read posts at Cognitive Daily that exposure to violent video games (and perhaps TV shows?) desensitizes people to violence within controlled, experimental laboratory settings, and that is an interesting finding. However, in examining the world outside of the lab, violent media cannot hope to account for even a trivial share of the variance across time in violent behavior.