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Monoamine oxidase A gene (MAOA) predicts behavioral aggression following provocation:

Monoamine oxidase A gene (MAOA) has earned the nickname “warrior gene” because it has been linked to aggression in observational and survey-based studies. However, no controlled experimental studies have tested whether the warrior gene actually drives behavioral manifestations of these tendencies. We report an experiment, synthesizing work in psychology and behavioral economics, which demonstrates that aggression occurs with greater intensity and frequency as provocation is experimentally manipulated upwards, especially among low activity MAOA (MAOA-L) subjects. In this study, subjects paid to punish those they believed had taken money from them by administering varying amounts of unpleasantly hot (spicy) sauce to their opponent. There is some evidence of a main effect for genotype and some evidence for a gene by environment interaction, such that MAOA is less associated with the occurrence of aggression in a low provocation condition, but significantly predicts such behavior in a high provocation situation. This new evidence for genetic influences on aggression and punishment behavior complicates characterizations of humans as “altruistic” punishers and supports theories of cooperation that propose mixed strategies in the population. It also suggests important implications for the role of individual variance in genetic factors contributing to everyday behaviors and decisions.

Regularly readers know we’ve talked about MAOA in the past, it’s one of those big-effect genes which keeps popping up in behavior genetic studies. It definitely increases my confidence in the reality of past associations to see it produce results in experimental situations which match our predictions. Along with the dopamine receptor loci this is likely a keeper. The issue of mixed strategies is something I’ve been mentioning periodically, the idea of evolutionary game theory has been around for nearly two generations, and frequency dependent selection is over a century old. But I think far too often people who are interested in the intersection between biology and behavior start conversations which assume that these are minor or trivial dynamics. At a certain point if “transient” states are more common than periods when there is an ESS, you need to reorient your frame. Human environments (that is, cultures) change a lot. Sometimes that change is exogenous (consider shifting climate), but in many cases instability in the background parameters upon which an ESS is conditional might result in periodic shifts in state.* Peter Turchin‘s work to some extent describes this on the macro-level, while Martin Nowak has developed models on a smaller scale. The main unfortunate byproduct of accepting this relatively more complex explanatory framework is that it makes glib assertions about natural selection on behavioral traits more difficult.

Here’s the ScienceDaily summary.

* Basically, if you figure out an “unbeatable” strategy at winning a game, you are screwed when the rules change.

Arnold Kling comments about my assertion that until recently cities were genetic black holes:

Today,. we think of cities as places where people come to thrive. Wealth is higher in cities than in small towns and rural areas. Richard Florida tells us that the creative class is to be found in cities.

…

I wonder: who came to cities? Was it people without land? Were cities like an awful lottery that people would play when they had no other choice? A bunch of landless people gathered together to prey on one another, with the winners thriving (moving to the country as soon as they could afford it) and the losers enduring a Hobbesian existence, where life was nasty, brutish and short?

My comment was a contention in relation to reproductive fitness; not quality of life or satisfaction (H/T to Greg Cochran for the observation). In the comments I cite a paper which suggests that city and rural divide in mortality favored the rural until around 1900 in the United States. The divide does not exist in large part due to proactive public health measures. Needless to say, though there were variations (e.g., compare 18th century London to Tokyo/Edo), in the pre-modern context public health was much more primitive.

So why move to the city? I think it is likely correct that city air makes one free. We can see this today as social change is occurring in Developing World megalopolises. In the ancient cities there were clear benefits for the poor, Rome and Constantinople had doles for the urban proletariat (though these doles were of course simply viable due to rents derived from their Empire). After the wars of the middle to late republic many impoverished peasants migrated to Rome to escape famine (the famine was exacerbated by the fact that many men were called up as soldiers to serve in foreign wars, and so their labor was missing). On the other hand, despite the dole there was often no regular employment. From the data I have seen modern urban-life worldwide tends to correlate with a lower fertility; and I see no reason this would not be so in the pre-modern world (I assume that the marginal return on “extra hands” provided by more children would likely be lower for a sporadically employed urban laborer than a farmer). But the main difference I suspect is disease load over time. Plagues regularly killed on the order of 50% of the population of ancient cities. After the population declines the cities would bounce back, but not through natural increase, but further waves of rural migrants. Rome’s population declined to tens of thousands in the medieval period, from on an order of 1 million in antiquity. I am skeptical of the idea that most modern Romans are descended from a demographic expansion of the medieval deme as opposed to migrants from the hinterland.

All the population genetic negatives are not to deny that civilization and the city are to a large extent identical (Sumer). Who says that cultural creativity or innovation has to track Darwinian fitness? Look at our own modern societies, the least successful by accepted measures are often the most “fit” in Darwinian terms.

Addendum: A shorthand way of thinking what I’m asserting, imagine two brothers who are farmers. One moves to the city to get on the bread dole, while the other attempts to make do on the margins. The former might have a higher chance of surviving, but because of the greater power of disease in the urban context the city brother is likely to have far fewer descendants than the country brother as periodically all of his descendants come under threat of dying in a plague (again, I also believe that fertility will be lower for urban descendants).

Sheril has a post up, On Sacrificing Reproductive Fitness For Career Advancement…, which makes a common sense point:

Angier references a recent survey of 160,000 Ph.D. recipients that found 70 percent of male tenured professors were married with children while only 44 percent of their female counterparts were. Further, twelve years or more after receiving doctorates, tenured women were more than “twice as likely as tenured men to be single and significantly more likely to be divorced.” Another California study reported nearly double the number of female faculty agree with the statement, “I had fewer children than I wanted,” compared to men. Angier sums it up:

I decided to check the mean number of hours worked last week against the number of children an individual had, and break that down by sex. Below the fold are the results.

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At ScienceBlogs, I posted on a new paper on Jewish genetics. At Taki’s Magazine I offer my opinion as to why labor and capital flows are qualitatively different, as well as some pedantic comments on points of Roman history. I wouldn’t be such a stickler on Roman history…but people just love to make analogies based on presumed correspondences. I’ve been meaning to review Peter Turchin’s new book, Secular Cycles, which you can read for free as a PDF. But if you recall how long my last post on his previous book was, it might be a little while in coming, so I encourage everyone to read Secular Cycles if the topic interests them. Finally, Ed Yong has a nice review of a new paper Language Phylogenies Reveal Expansion Pulses and Pauses in Pacific Settlement (the paper is in Science, but it doesn’t seem online yet).

Carl Zimmer pointed me to a new paper, A genome-wide genetic signature of Jewish ancestry perfectly separates individuals with and without full Jewish ancestry in a large random sample of European Americans. The title is so informative that pasting the abstract is almost unnecessary, but here is the conclusion which gets to the point:

In conclusion, we show that, at least in the context of the studied sample, it is possible to predict full Ashkenazi Jewish ancestry with 100% sensitivity and 100% specificity, although it should be noted that the exact dividing line between a Jewish and non-Jewish cluster will vary across sample sets which in practice would reduce the accuracy of the prediction. While the full historical demographic explanations for this distinction remain to be resolved, it is clear that the genomes of individuals with full Ashkenazi Jewish ancestry carry an unambiguous signature of their Jewish heritage, and this seems more likely to be due to their specific Middle Eastern ancestry than to inbreeding.

There have been other papers which show that Ashkenazi Jews form a separate cluster from gentile whites in the United States. This is important again in the context of biomedical studies attempting to ascertain the genetic roots of particular diseases; population substructure (e.g., Jew vs. non-Jew) may result in confounded associations. Also, one of the authors of the paper is David Goldstein, author of the fascinating Jacob’s Legacy.
In any case, on to the PC charts where the real action is. Do note that I’ve resized and added explanatory labels here & there for clarity.

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The Department of Children, Schools and Families in Great Britain has released its report for 2007/2008 breaking down nationwide educational attainment by pupil characteristics, including race. Actually, the report was released in November, but I was holding off on posting about it because I was under the erroneous impression that updated, race-specific data would be provided in mid-January.

DavidB has posted on previous reports for 2002, 2003/2004, 2005, and 2006/2007. Some readers might be interested in my summary of the 2007/2008 GCSE results for racial and ethnic groups in England, which I’ve posted here.

The Monito del Monte is the only extant member of its order, the Microbiotheria. This order is itself part of the superorder Australidelphia, which includes Australian Marsupials and the Monito del Monte, whose native habitat are the forests of Chile and Argentina. In other words, the Monito del Monte is more closely related to the Marsupials of Australia than to those of the New World.

Market forces affect patterns of polygyny in Uganda:

Polygynous marriage is generally more beneficial for men than it is for women, although women may choose to marry an already-married man if he is the best alternative available. We use the theory of biological markets to predict that the likelihood of a man marrying polygynously will be a function of the level of resources that he has, the local sex ratio, and the resources that other men in the local population have. Using records of more than 1 million men in 56 districts from the 2002 Ugandan census, we show that polygynously married men are more likely to own land than monogamously married men, that polygynous marriages become more common as the district sex ratio becomes more female biased, that owning land is particularly important when men are abundant in the district, and that a man’s owning land most increases the odds of polygyny in districts where few other men own land. Results are discussed with reference to models of the evolution of polygyny.

My piece for The Guardian, Monogamy: bucking the trend?, was fundamentally an argument against natural short term market forces.

Evidence of gender differences in the ability to inhibit brain activation elicited by food stimulation:

Although impaired inhibitory control is linked to a broad spectrum of health problems, including obesity, the brain mechanism(s) underlying voluntary control of hunger are not well understood. We assessed the brain circuits involved in voluntary inhibition of hunger during food stimulation in 23 fasted men and women using PET and 2-deoxy-2[18F]fluoro-D-glucose (18FDG). In men, but not in women, food stimulation with inhibition significantly decreased activation in amygdala, hippocampus, insula, orbitofrontal cortex, and striatum, which are regions involved in emotional regulation, conditioning, and motivation. The suppressed activation of the orbitofrontal cortex with inhibition in men was associated with decreases in self-reports of hunger, which corroborates the involvement of this region in processing the conscious awareness of the drive to eat. This finding suggests a mechanism by which cognitive inhibition decreases the desire for food and implicates lower ability to suppress hunger in women as a contributing factor to gender differences in obesity.

ScienceDaily has a lot more:

“The finding of a lack of response to inhibition in women is consistent with behavioral studies showing that women have a higher tendency than men to overeat when presented with palatable food or under emotional distress,” Wang said. “This decreased inhibitory control in women could be a major factor contributing to the observed differences in the prevalence rates of obesity and eating disorders such as binge eating between the genders, and may also underlie women’s lower success in losing weight while dieting when compared with men.”

Here’s a question: do the sexes differ in time preference?