As is normally the case, my annual list comprises the best books I have read in the past year, irrespective of their date of release. I read fewer books this year than usual, so I’m drawing from a smaller pool than for the last couple of years (2010 and 2011). Here are my favourite six for 2012:

Passions Within Reason: The Strategic Role of the Emotions by Robert Frank (my review): A book I should have read a long time ago. I particularly appreciated Frank’s use of path-dependent evolution to develop his model of human behaviour.

The Righteous Mind: Why Good People Are Divided by Politics and Religion by Jonathan Haidt (my review): At the top of many lists for good reason.

Adapt: Why Success Always Starts with Failure by Tim Harford (my review): Apart from being interesting and full of reasonable advice, Harford demonstrates a deep understanding of evolutionary processes, which is not often the case in books of this nature.

Thinking, Fast and Slow by Daniel Kahneman (my review): Magnificent. The clear and accessible way that each chapter illustrates a bias or heuristic makes it the best book on rationality and decision-making that I have read.

Moby Dick by Herman Melville: The best classic I read this year. Although I could have skipped some of the detours, many are fascinating.

Darwinian Politics: The Evolutionary Origin of Freedom by Paul Rubin (my review): A strong argument for political institutions that maximise freedom.

There are a few books that I read this year that have me in two minds, so I haven’t included them in the above list. I enjoyed Ridley’s The Rational Optimist: How Prosperity Evolves  (my review), but despite his claims to the contrary, Ridley stretched the evolutionary metaphor too far in drawing a Panglossian case. Robert Trivers’s The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life (my review) would have required a much more thorough editing to make this list. I also enjoyed Kevin Kelly’s What Technology Wants (my review), despite not buying the central argument.

Of the books I have in my reading pile, I still haven’t got to Pinker’s The Better Angels of Our Nature: Why Violence Has Declined, and I intend to read Flynn’s Are We Getting Smarter?: Rising IQ in the Twenty-First Century over the Christmas break (edit: review here). Hopefully they will crack next year’s list.

John Kay writes:

A narrow focus is characteristic of scientific method but gets in the way of understanding social phenomena. …

The economists who argue that the rationale of the family is found in cost savings have a point. Two together can live more cheaply than two separately, if not as cheaply as one. But anyone who thinks the quest for scale economies is the primary explanation of the human desire for family life is strangely deficient in observational capacity, as well as common sense.

The “economics of the family” is a prime example of an economic imperialism that seeks to account for all behaviour through a distorted concept of rationality, an extreme example of economists’ notorious physics envy.

Rationality is a powerful tool in the economic toolkit, and the lens of natural selection is a powerful rationalising agent. But what is the objective we are rationally trying to achieve in forming a family? Likely not the minimisation of costs. And what powers do we have to achieve that objective? Not perfect foresight and calculating ability. The application of economic tools with an understanding of the agent’s objectives and the bounded nature of human rationality is the more fruitful exercise.

David Dobbs has written a great National Geographic piece on the human compulsion to explore. At the centre of the article is the question of genetic influence.

First, on whether migration has a genetic basis:

[T]here is a mutation that pops up frequently in such discussions: a variant of a gene called DRD4, which helps control dopamine, a chemical brain messenger important in learning and reward. Researchers have repeatedly tied the variant, known as DRD4-7R and carried by roughly 20 percent of all humans, to curiosity and restlessness. …

Most provocatively, several studies tie 7R to human migration. The first large genetic study to do so, led by Chuansheng Chen of the University of California, Irvine in 1999, found 7R more common in present-day migratory cultures than in settled ones. …

Another recent study backs this up. Among Ariaal tribesmen in Africa, those who carry 7R tend to be stronger and better fed than their non-7R peers if they live in nomadic tribes, possibly reflecting better fitness for a nomadic life and perhaps higher status as well. However, 7R carriers tend to be less well nourished if they live as settled villagers. The variant’s value, then, like that of many genes and traits, may depend on the surroundings. A restless person may thrive in a changeable environment but wither in a stable one; likewise with any genes that help produce the restlessness. …

I’m not sold on the DRD4-7R variant story yet, but I am open to the idea that there is a basket of traits that differ between migrants and those who stay. If that is the case, the interesting question is what effect those traits have in other spheres. For example, Galor and Michalopoulos note the DRD4-7R variant in their argument that selection for entrepreneurial traits plays a role in the economic development process. Are migrants naturally more entrepreneurial?

Of course, those who migrate may be different from those they leave simply through chance:

[A] migratory wave can concentrate not just particular types of people on its frothy front edge; it can also concentrate and aid the expansion of any genes that may encourage those people to migrate.

Sometimes a gene rides such a wave passively, more or less by accident—the gene just happens to be common in the leading migrators, so it becomes common in the communities they establish. …

But a migratory wave can also allow genes friendly to migration to drive their own selection. …

Laurent Excoffier, a population geneticist at the University of Bern, thinks something similar occurred with the Quebec loggers. In a 2011 paper Excoffier and some colleagues analyzed centuries of Quebec parish birth, marriage, settlement, and death records and found that the pioneer families behaved and bred in a way that spread both their genes and the traits that drove them to the front. These wave-front couples married and mated sooner than did couples back home, perhaps because they were more impatient folks to begin with and because the frontier gave them access to land and a social atmosphere favorable to starting sooner. This alone produced more children than the “core” families who stayed behind did (9.1 per family versus 7.9, or 15 percent more). … In this case it rapidly raised the share of these families’ genes and cultures within their own population—and thus within North America’s larger population.

Excoffier believes that if this “gene surfing,” as some call it, happened often as humans scattered around the globe, it would have selected for multiple genes that favor curiosity, restlessness, innovation, and risk taking. This could, he says, “help explain some of our exploratory behavior.”

Migration provides an opportunity for strong selection through the new environment that the migrants are exposed to, possibly favouring traits that were neutral or deleterious in the earlier environment. Even if migrants are no different from those they leave, it may not stay the case for long.

As an end note, Razib rightfully asks whether heritability is a better place to focus in exploring this genetic link than looking for genes such as DRD4-7R. I think this is the case in a lot of fields in the short term, including genoeconomics.

The Smithsonian magazine has an interview with James Flynn about his book Are We Getting Smarter? (HT: Annie Murphy Paul) First, Flynn on the “bright tax:

The wisdom always was that the brighter you were, the less your mental abilities declined in old age. I found that was an oversimplification. It is true of verbal intelligence. The brighter you are, the more you get a bonus for verbal skills. I call that a “bright bonus.” Your vocabulary declines at a much less steep rate in old age than an ordinary or below average person. But to my amazement I found that for analytic abilities it was just the reverse. There is a “bright tax.” The brighter you are, the quicker after the age of 65 you have a downward curve for your analytic abilities. For a bright person, you go downhill faster than an average person.

This raises an interesting question. Is it something to do with the aging brain, or does it have to do with environment? It could be that a good analytic brain is like a high performance sports car; it just requires more maintenance, and in old age, the body can’t give it. That would be a physiological explanation; the bright brain requires sustenance from the body, which as the body ages is no longer forthcoming. The environmental explanation would be that we use our analytic abilities mainly at work. That means that if a bright person is in a cognitively demanding profession, they are like an athlete; they build up a big exercise advantage over the average person, who has a humdrum job. Then, retirement would be a leveler. That is, if you give up work at 65, you are like an athlete who is retired from competition. You no longer have that exercise advantage of your analytic abilities that work affords. We don’t really know which of these things is true. It could be that they are both true to some degree.

Also, a prediction of the next 100 years:

In my book, I study six developing nations. Kenya is undergoing explosive IQ gains. Brazil and Turkey are undergoing quite profound gains. Nations like Saudi Arabia and the Sudan are not, but the Sudanese keep having civil wars and the Saudis are really just living off of oil revenue. They are not industrializing in any real sense. Dominica is the sixth case. There, they are making IQ gains, but their infrastructure is wiped out about every 10 years by hurricanes, earthquakes and tsunamis. I predict that Brazil, Turkey and Kenya will industrialize over the next century and begin to rival the Western world for IQ.

I’ve posted before about Paul Krugman’s dislike of the work of Stephen Jay Gould, but I have come across another old essay in which Krugman weighs in on the question of Gould’s role in communicating evolutionary biology. Krugman argues that Gould was attractive to readers because he made no attempt to explain the mathematical logic of evolutionary theory. Krugman writes:

Ask a working biologist who is the greatest living evolutionary thinker, and he or she will probably answer John Maynard Smith (with nods to George Williams and William Hamilton). Maynard Smith not only has a name that should have made him an economist; he writes and thinks like an economist, representing evolutionary issues with stylized mathematical models that are sometimes confronted with data, sometimes simulated on the computer, but always serve as the true structure informing the verbal argument. A textbook like his Evolutionary Genetics (1989) feels remarkably comfortable for an academic economist: the style is familiar, and even a good bit of the content looks like things economists do too. But ask intellectuals in general for a great evolutionary thinker and they will surely name Stephen Jay Gould — who receives one brief, dismissive reference in Maynard Smith (1989). …

What does Gould have that Maynard Smith does not? He is a more accessible writer — but evolutionary theory is, to a far greater extent than economics, blessed with excellent popularizers: writers like Dawkins (1989) or Ridley (1993), who provide beautifully written expositions of what researchers have learned. (Writers like Gould or Reich are not, in the proper sense, popularizers: a popularizer reports on the work of a community of scholars, whereas these writers argue for their own, heterodox points of view). No, what makes Gould so popular with intellectuals is not merely the quality of his writing but the fact that, unlike Dawkins or Ridley, he is not trying to explain the essentially mathematical logic of modern evolutionary theory. It’s not just that there are no equations or simulations in his books; he doesn’t even think in terms of the mathematical models that inform the work of writers like Dawkins. That is what makes his work so appealing. The problem, of course, is that evolutionary theory — the real thing — is based on mathematical models; indeed, increasingly it is based on computer simulation. And so the very aversion to mathematics that makes Gould so appealing to his audience means that his books, while they may seem to his readers to contain deep ideas, seem to people who actually know the field to be mere literary confections with little serious intellectual content, and much of that simply wrong. In particular, readers whose ideas of evolution are formed by reading Gould’s work get no sense of the power and reach of the theory of natural selection — if anything, they come away with a sense that modern thought has shown that theory to be inadequate.

Krugman’s larger question in the essay is why the concept of comparative advantage is so hard to communicate. One reason is that comparative advantage, like evolutionary theory, has at its base a mathematical model. The whole essay is worth the read (as is most Krugman from that era).

A few weeks ago, Bryan Caplan pointed out this great working paper by David Hedengren and Thomas Stratmann:

The Dog that Didn’t Bark: What Item Non-Response Shows about Cognitive and Non-Cognitive Ability 

What survey respondents choose not to answer (item non-response) provides a useful task based measure of cognitive ability (e.g., IQ) and non-cognitive ability (e.g., Conscientiousness). Using the German Socio-Economic Panel (SOEP) and the National Longitudinal Survey of Youth 1997 (NLSY97), we find consistent correlation between item non-response and traditional measures of IQ and Conscientiousness. We also find that item non-response is more strongly correlated with earnings in the SOEP than traditional measures of either IQ or Conscientiousness. We also use the Survey of Income and Program Participation (SIPP) Gold Standard, which has no explicit measure of either cognitive or non-cognitive ability, to show that item non-response predicts earnings from self-reported and administrative sources. Consistent with previous work showing that Conscientiousness and IQ are positively associated with longevity, we document that item non-response is associated with decreased mortality risk. Our findings suggest that item non-response provides an important measure of cognitive and non-cognitive ability that is contained on every survey.

The triumph of this paper is the mass of survey data to which this technique can be applied. As the authors state in the opening paragraph:

Studying the importance of non-cognitive skills, such as conscientiousness, perseverance, and motivation, has been hamstrung by the fact that many popular data sets in economics do not contain information on an individual’s personality traits. However, surveys contain a valuable but neglected piece of data: what respondents do not say. Respondents skip, refuse to answer, or claim ignorance on at least a few questions in virtually all surveys. When a respondent forgets to fill in answers to some questions on the survey form, or refuses to provide an answer to the interviewer, we gain important information about the respondent.

Tomas Rees points to an interesting paper by Marcus Jokela, who examined how the fertility rates of Americans born between 1920 and 1960 were affected by their personality.

Using the big five personality traits – openness, conscientiousness, extraversion, agreeableness and neuroticism – Jokela found that higher levels of conscientiousness in women and higher levels of openness in both sexes became more strongly related to low fertility as time went on. Effectively, cultural conservatives are now more likely to have higher fertility.

Using this result, Rees argued that religiosity is not evolutionarily advantageous due to higher fertility, even though current fertility trends may make it seem so. Rather, the link is between conservative values and fertility, and this link is relatively recent.

I appreciate this argument, largely because it highlights the inconsistency and looseness in the way many studies define phenotypes. Is religiosity just a manifestation of someone’s big five personality traits? We consistently see new papers about the heritability and evolutionary advantage of various political views, happiness, religious persuasions, income and so on. But ultimately, many of these analyses are versions of the same theme, and the analysis could be hardened by deciding on some firm phenotypic traits on which to conduct the analysis. For example, most religious views can probably be captured through the big five personality traits and IQ. I have previously made a similar point about the heritability of political views. If the analyses were linked to a consistent set of phenotypic traits, we would be better positioned to compare results, look at them through time and to explore the underlying causal mechanisms.

Jokela’s paper also highlights that a trait may become advantageous or not with changes in the environment. Heritable variation in reproductive outcomes is often evidence that the evolutionary advantage is relatively recent. After all, evolution eliminates variation. As a result, particularly in modern contexts, we need to consider what environmental shocks have played out. We can make a coherent story about Jokela’s findings using that framework, with changes in the social environment between 1920 and 1960 allowing those who were more open to experience to choose the alternative low fertility option.

A new Nature paper by Fu and colleagues has been the subject of a few good write-ups. First, from Brandon Keim at Wired:

In the most massive study of genetic variation yet, researchers estimated the age of more than one million variants, or changes to our DNA code, found across human populations. The vast majority proved to be quite young. The chronologies tell a story of evolutionary dynamics in recent human history, a period characterized by both narrow reproductive bottlenecks and sudden, enormous population growth.

The evolutionary dynamics of these features resulted in a flood of new genetic variation, accumulating so fast that natural selection hasn’t caught up yet. As a species, we are freshly bursting with the raw material of evolution.

“Most of the mutations that we found arose in the last 200 generations or so. There hasn’t been much time for random change or deterministic change through natural selection,” said geneticist Joshua Akey of the University of Washington, co-author of the Nov. 28 Nature study. “We have a repository of all this new variation for humanity to use as a substrate. In a way, we’re more evolvable now than at any time in our history.” …

Put simply, more people means more mutations, and in a growing population, there is less chance that those mutations will be lost through drift.

Despite their young age, these new variants are relevant for our recent evolutionary history. As pointed out by Greg Cochran, if you couple this explosion in new variants with the large changes in selection pressures associated with the shift to agriculture, you would see adaptive evolution in humans speed up.

The different population dynamics associated with African and European populations is also interesting. More from Keim:

Also playing a role are the dynamics of bottlenecks, or periods when populations are reduced to a small number. The out-of-Africa migration represents one such bottleneck, and others have occurred during times of geographic and cultural isolation. Scientists have shown that when populations are small, natural selection actually becomes weaker, and the effects of randomness grow more powerful. …

The result, calculated Akey, is that people of European descent have five times as many gene variants as they would if population growth had been slow and steady. People of African descent, whose ancestors didn’t go through that original bottleneck, have somewhat less new variation, but it’s still a large amount: three times more variation than would have accumulated under slow-growth conditions.

This finding is an interesting fit with the argument of Ashraf and Galor linking genetic diversity and economic development. As genetic diversity results in a wider spectrum of traits in the population, it is more likely that there will be traits complementary to technological advance. The measure of diversity used by Ashraf and Galor, expected heterozygosity, is based on the probability that two randomly selected people will differ with respect to a certain gene, averaged over all measured genes. As people migrated from Africa through Europe and beyond, they migrated out with only a subset of the available genetic variation in the population, and therefore, expected heterozygosity declines with distance from Africa. But as the paper by Fu and colleagues shows, the prevalence rare variants does not decline with distance from Africa. Could these additional rare variants in some populations increase the probability that there will be traits complementary to technological advance?

Also worth reading is the post from John Hawks. Hawks raises some questions around the estimated age of the variants (are they older than they seem?) and asks whether some of these rare variants came from Neanderthals.

In Forbes, Jon Entine discusses the rise of “positive eugenics”:

Scientists offered what they considered to be a progressive solution: “positive eugenics,” which would encourage society’s healthiest citizens to have more children—the founder of Planned Parenthood, Margaret Sanger, was an eager proponent of eugenics—and more tentatively, “negative eugenics.”The “negative” wing of eugenics prevailed, however, which for the most part meant restricting the mentally ill, poor, immigrants and non-whites from propagating. It served as an inspiration and justification for Nazism and the “Final Solution,” which led to the discrediting of the entire movement.

Now, eugenics is back in vogue with a clear focus on the positive role that genetics can and is playing in medicine and health. …

[M]odern eugenics aspirations aren’t about top-down measures promoted by the Nazis or the forced sterilizations of the past, as Comfort points out. Instead of being driven by a desire to improve the species, new eugenics is being driven largely by the individual’s personal desire to be as healthy, intelligent and attractive as possible—and for our children to be so.

Entine focuses on medical interventions, such as the testing of foetuses, and hints at the ethical debates about more controversial areas such as choice of sex and genetic enhancement. While he does not go into enhancement in detail, Entine links to an interesting post at Gene Expression, where Razib asks how “positive eugenics” might  be implemented for traits such as intelligence. As a huge number of gene variants affect intelligence, genetic screening for intelligence is not an easy task. Razib argues that this will cause the initial focus to be on mutation load. If intelligence is highly vulnerable to mutations, with variation in intelligence largely due to negative mutations, reducing mutation load will probably be a long-term approach too.

Interestingly, some of the “positive eugenics” discussed by Entine does not reduce the frequency of harmful alleles in the population, but rather affects the frequency in which they express themselves in the population. For example, the incidence of Tay Sachs disease has been reduced due to screening in Jewish populations. As the disease only manifests when someone possesses both disease-related alleles, the prevention of marriage between carriers of the alleles stops their children from having the disease. But the disease-related allele can still be harmlessly present in the next generation. Further, if there were a positive effect from carrying only one of these alleles, which is suggested by the spread of the allele despite the high costs to the disease, screening could actually increase the prevalence.

Finally, as I have posted before, a positive eugenics program has been ongoing for millions of years through our selection of partners with whom we wish to have children. We are still some way from using modern technologies to shape out genetic future to the extent that sexual selection already does.

Henry Harpending writes:

In 1300 the homicide rate was about 50 per 100,000 people, or 0.5 per thousand. Homicide must have caused on the order of 1 to 2 percent of all deaths and a much higher proportion of deaths of young adult males. Our assumption of a Normal distribution of the underlying trait immediately implies that the threshold was 3.3 standard deviations greater than the mean (from any table of the Normal distribution). Natural selection, social selection we would say in this case, disfavors homicide and the distribution is shifted so that the homicide threshold is surpassed by only 1 in 100,000 people rather than 1 in 2,000. By the year 2000 the homicide threshold is at 4.3 standard deviation from the population mean. In other words selection has moved the distribution 1 standard deviation in 700 years or 28 generations. …

In the present case we need a response of 1/28 of a standard deviation per generation. Assuming an additive heritability of 0.5 (the true value is probably 0.8 or so from literature on the heritability of aggressive behavior in children) the selective differential must be about 1/14 or .07 standard deviations per generation. In terms of IQ this would correspond to a one point IQ advantage of parents over the population average and in terms of stature parents with a mean stature 0.2 inches greater than the population average. This would occur if the most homicidal 1.5% of the population were to fail to reproduce each generation.

If homicides were responsible for one to two per cent of all deaths around 1300, it seems, on face value, unlikely that the most homicidal 1.5% would fail to reproduce. If the effect was direct, that would require most murderers to reach an evolutionary dead-end. But as Harpending notes in the comments to his post:

[W]e think (most of us) that homicide is an indicator of something else—proneness to violence, high time preference, fast life history, and so on. We cannot treat homicide as a discrete real trait. It is instead a shadow on the wall of the cave.

If those who had lower rates of time preference and who were less risk seeking gained a fitness advantage from success in apparently unrelated domains such as commerce, the effects would almost certainly play out in the context of violent behaviour.

Harpending’s post also reminds me that quantitative genetics is a severely underused tool on questions such as these.