Average human brain size has declined for 20,000 years, a stark contrast to the steady increase over the preceding millions. While I would argue that translation of this reduced brain size into lower intelligence would have a negative result, I am not convinced that intelligence has dropped over that time.

Eighteen months ago, Discover magazine published an article by Kathleen McAuliffe on the shrinking brain phenomenon and what this means for intelligence. On the idiocracy side of the debate was David Geary and Drew Bailey:

[T]he Missouri team used population density as a proxy for social complexity, reasoning that when more people are concentrated in a geographic region, trade springs up between groups, there is greater division of labor, the gathering of food becomes more efficient, and interactions among individuals become richer and more varied.

Bailey and Geary found population density did indeed track closely with brain size, but in a surprising way. When population numbers were low, as was the case for most of our evolution, the cranium kept getting bigger. But as population went from sparse to dense in a given area, cranial size declined, highlighted by a sudden 3 to 4 percent drop in EQ starting around 15,000 to 10,000 years ago. “We saw that trend in Europe, China, Africa, Malaysia—everywhere we looked,” Geary says.

The observation led the researchers to a radical conclusion: As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive. As Geary explains, individuals who would not have been able to survive by their wits alone could scrape by with the help of others—supported, as it were, by the first social safety nets.

In a Malthusian world where incomes hover around subsistence levels, population density is proportional to the level of technology available to the population. Population density is not something that simply arises, but it is enabled by the technology which allows for the required level of subsistence to be produced for a larger population in a given area. As a result, I am not convinced by Bailey and Geary’s conclusion. If we need a higher level of technology to support higher population density, and average intelligence of the population is related to technology, you would expect higher intelligence populations to have higher population densities.

As for their concerns about the dysgenics of the first social safety nets (I wonder what their views are about the modern ones), I am not convinced that higher populations delivered such survival benefits to the dumb. With a larger, more dense society comes trade, specialisation and more complex social arrangements, all of which are likely to favour those with higher intelligence. Plus, if there was such a social net, why wasn’t it also supporting those huge brained people who were burning too much energy to survive? If we throw sexual selection into the mix, the benefits to intelligence appear larger.

John Hawks puts a different spin on Bailey and Geary’s data, which may reconcile the Malthusian assumptions with the brain size observations:

The organ is such a glutton for fuel, he says, that it gobbles up 20 percent of all the calories we consume. “So although a bigger brain can presumably carry out more functions, it takes longer to develop and it uses more energy.” Brain size probably depends on how those opposing forces play out.

The optimal solution to the problem, he suggests, “is a brain that yields the most intelligence for the least energy.” For evolution to deliver up such a product, Hawks admits, would probably require several rare beneficial mutations—a seeming long shot. But a boom in the human population between 20,000 and 10,000 years ago greatly improved the odds of such a fortuitous development. He cites a central tenet of population genetics: The more individuals, the bigger the gene pool, and the greater the chance for an unusual advantageous mutation to happen. …

Hawks notes that such changes would be consistent with the many brain-related DNA mutations seen over the past 20 millennia. He speculates that the organ’s wiring pattern became more streamlined, the neurochemistry shifted, or perhaps both happened in tandem to boost our cognitive ability.

While bigger brains lead to greater intelligence (there is a positive correlation in modern populations), intelligence is not all about size. More efficient arrangements may result in a better energy-intelligence trade-off, delivering more efficient, smaller but smarter brains. The continued strong selection of alleles associated with brain size is also suggestive of this.

As an end note, brain size has been back on an increasing trend for the last 200 years, and there is some suggestion that this is not all environmental:

Since evolution does not happen overnight, one would assume this sudden shift (much like the increase in height and weight) is unrelated to genetic adaptations. Hawks, for instance, says the explanation is “mostly nutrition.” Jantz agrees but still thinks the trend has “an evolutionary component because the forces of natural selection have changed so radically in the last 200 years.” His theory: In earlier periods, when famine was more common, people with unusually large brains would have been at greater peril of starving to death because of gray matter’s prodigious energy requirements. But with the unprecedented abundance of food in more recent times, those selective forces have relaxed, reducing the evolutionary cost of a large brain.

Of course, as Geary may point out, the survival cost of a small brain’s lack of intellectual horsepower is also well down.

Matt Ridley writes on the fossil evidence that human brains have shrunk from around 1,500 cubic centimetres to 1,350 cubic centimetres over the last 20,000 years:

This neither worries nor surprises me. We ceased relying upon individual brain power tens of thousands of years ago. Our civilization now gets all its inventive and creative power from the linking of brains into networks. Our future depends on being clever not individually, but collectively.

Ridley’s reason for not worrying is at odds with evidence that the return to an increase in an individual persons IQ is lower than that for an equivalent increase in average IQ for a population.

Take this factoid from Garett Jones’s website (I have blogged about work by Jones before, including here and here):

A two standard deviation rise in an individual person’s IQ predicts only about a 30% increase in her wage.  But the same rise in a country’s average IQ score predicts a 700% increase in the average wage in that country.

There are massive positive externalities to a population having a higher average IQ. Ridley is right to point to the networked nature of intelligence, but those networks result in large benefits to being surrounded by high IQ people. If I considered that intelligence were declining along with brain size (I’m not, which is a subject for a later post), I would be worried.

Richard Conniff’s Yale Alumni Magazine article on Irving Fisher’s support of eugenics has some great stories (HT Arnold Kling), but one of the closing paragraphs caught my attention.

We know better now, of course. And yet eugenic ideas still linger just beneath the skin, in what seem to be more innocent forms. We tend to think, for instance, that if we went to Yale, or better yet, went to Yale and married another Yalie, our children will be smart enough to go to Yale, too. The concept of regression toward the mean—invented, ironically, by Francis Galton, the original eugenicist—says, basically: don’t count on it. But outsiders still sometimes share our eugenic delusions. Would-be parents routinely place ads in college newspapers and online offering to pay top dollar to gamete donors who are slender, attractive, of the desired ethnic group, with killer SAT scores—and an Ivy League education.

Regression to the mean often gets trotted out in discussion of eugenics or human evolution, but it is a misunderstanding of the concept. If we eliminated the bottom half of the population by measured IQ, the average IQ of that population will change as the underlying genotype will have changed. The next generation will not have as high IQ as the survivors, as we would have eliminated some people with high-IQ genotypes who had low phenotypic IQ due to luck or environment, and vice versa. However, that population and their descendants will have a higher mean than the original population. Gregory Clark amusingly pointed out the evolutionary implications of the regression to the mean argument in response to critiques (pdf) of his book A Farewell to Alms:

Adapting one of Bowles’s points McCloskey tries to land a knockout blow. Regression to the mean would in a few generations destroy any effects of ‘survival of the richest’ on behavior, by taking descendants back to the average characteristics of the population. Such selection could thus only influence behavior for any descendants of the economically successful for a few generations.

This is just a misunderstanding of the concept of regression to the mean. If McCloskey was right, farmyard animals would all be at their medieval sizes still, and instead of the wonderful modern extravagance of dog breeds, all dogs would have the characteristics of wolves and would make bad house pets. As a further reductio ad absurdum, humans would never have evolved from apes in the first place. Why haven’t creationists latched onto this wonderful insight, which, according to McCloskey, Galton, the great social Darwinist, fully appreciated (and yet clung to social Darwinism)?

The problem with eugenics is not that it could not change the average of traits in the population. The stronger arguments rest on human decency, freedom from interference, untended consequences and the tyranny of government.

Conniff’s example of seeking a high-IQ Yalie as a mate has another amusing problem. The process of selecting mates and the evolutionary result is known as sexual selection. As described in Geoffrey Miller’s The Mating Mind, sexual selection may have shaped our brains as those with higher intelligence were more reproductively successful.  Those who did not seek intelligent, attractive mates are no longer with us as their unintelligent, ugly children left no descendants. The process of seeking suitable mates described by Conniff , whatever the difficulty in observing the traits we care about, is not delusional. It is also a large reason why we are as we are.

Last week’s edition of Science has an interesting article by Sam Bowles on the role of conflict on human social evolution. Bowles covers some familiar ground on the debate around the role of group selection in shaping human altruistic preferences:

Bowles cites his theoretical models that show this point, but is there any society whose warlike behaviour against other groups extended to elimination of the women of their vanquished rival? If any of the women of the defeated group are absorbed into the victor, there will be substantial gene flow. Add exogamy to the mix, and I struggle to see how a human group could maintain the required level of genetic differentiation.

Bowles has a number of other interesting threads in the article. The most novel of these is the manner in which he links conflict with the modern liberal state. Bowles writes:

Seven centuries ago, in what is now Italy, there were more than 200 distinct independent governing entities. Europe was governed by about 500 sovereign bodies: “empires, city states, federations of cities, networks of landlords, religious orders, leagues of pirates, warrior bands”. By World War I, fewer than 30 remained. A single political form had survived: the national state, a centralized bureaucratic structure maintaining order over a defined territory, with the capacity to mobilize substantial resources by taxation and borrowing and to deploy permanent armed forces.

What explains the competitive success of this novel form of rule? The simple answer is that national states won wars.

This battle then continued within the state:

American high school students are taught that their democratic constitution was the gift of the landed and commercial elites of the 13 former colonies. James Madison and the other authors of The Federalist Papers, the story goes, convinced the haves that the have nots would never be able to unite sufficiently to redistribute wealth. The elites could safely take a chance on democracy. But that is just one of America’s national myths. The United States would wait more than a century and a half to meet the elementary standard of democratic rule by extending suffrage to virtually all adults (with the Voting Rights Act of 1965), a process propelled by the victories of abolitionists, slaves and their descendants, workers, and women demanding the vote .

A natural corollary to the argument that group conflict was important in shaping human traits and our institutions is the question about whether that must necessarily have negative implications for conflict today. Bowles is optimistic on this front:

It seems likely, too, that conflict will remain important for human progress. But does this require the violence, suffering, bigotry, and waste characteristic of the conflicts of the past along with the cultural inheritance of this dismal trajectory, an unpleasant nexus of predispositions that Choi and I call “parochial altruism,” marked by generosity toward those we call “us” and hostility and intolerance toward “them” ?

As is often the case, the whole article is worth a read.

I enjoyed the responses to Michael Sandel’s critique of markets in the How Markets Crowd Out Morals forum on the Boston Review website. Sandel’s essay follows in the wake of his new book, What Money Can’t Buy: The Moral Limits of Markets.

Most of the response are worth reading, but I particularly enjoyed the one by Herb Gintis. Some of the more interesting parts of Gintis’s piece were as follows:

The idea that some valuable things should not be bought and sold on markets has been known for centuries, certainly since the anti-slavery movement in England. All mature economists understand this well. Just because some otherwise-obscure economist can gain fifteen minutes of fame by advocating the suppression of non-monetary gift-giving doesn’t mean we should interpret his claims as an exercise of brilliant economic argument. …

By focusing on the marketability of particular things, Sandel misses the larger effect of an economy regulated by markets on the evolution of social morality. Movements for religious and lifestyle tolerance, gender equality, and democracy have flourished and triumphed in societies governed by market exchange, and nowhere else.

My colleagues and I found dramatic evidence of this positive relationship between markets and morality in our study of fairness in simple societies—hunter-gatherers, horticulturalists, nomadic herders, and small-scale sedentary farmers—in Africa, Latin America, and Asia. … [W]e measured the degree of market exposure and cooperation in production for each society, and we found that the ones that regularly engage in market exchange with larger surrounding groups have more pronounced fairness motivations. The notion that the market economy makes people greedy, selfish, and amoral is simply fallacious.

As an aside, an interesting question is the direction of causation between markets and morality. I suspect the emergence of markets is endogenous to the characteristics of the populations in which they emerge.

When measured against his fantastic The Company of Strangers, Paul Seabright’s new book The War of the Sexes: How Conflict and Cooperation Have Shaped Men and Women from Prehistory to the Present was always facing a tough task. The War of the Sexes contains some interesting insights, and it is accessible and easy to read. However, some parts of the book feel flat.

Part of my reaction stems from the first half of the book, titled “Prehistory”, which contains little new for someone who is well-read in evolutionary biology. It is a great introduction to sexual selection, signalling, sexual conflict and the evolutionary basis for male-female differences, but it contains few surprises for someone who might have read, say, Geoffrey Miller’s The Mating Mind and Spent, or Matt Ridley’s The Red Queen.

One novel thread in the first half concerns Seabright’s views on the change in the relative power of women as societies transitioned from hunter-gathering to agriculture to modern society. Seabright considers that men in agricultural societies had an increased ability to confine women relative to what they had previously. Unfortunately, we only get a taste of this idea because, as noted in reviews by Arnold Kling and John Whitfield, Seabright spends little time on the transition.

My equivocal feelings extended to the next two chapters where Seabright discusses whether talent or occupational preferences might explain differences in outcomes for men and women. Seabright implicitly rejects these explanations. I say implicitly as Seabright does not state this as a direct conclusion, but instead focuses on undermining assumptions that might be made for the other side. For example, he notes the greater prevalence of men at the very high end of mathematics performance and states that this should not be assumed to immediately carry over into economic value, rather than seeking to address whether it might be true. Similarly, when he notes that men and women have different occupational preferences, his major area of exploration is their respective preferences for competition. But what of winner take all professions or scalability? Or desire for power and influence? Maybe they are not the answer, but Seabright prefers to chip at particular points rather than taking on the whole issue and drawing strong conclusions.

I expect Seabright’s approach is partly driven by a desire to be even-handed, which he is gallantly so in an area where many authors are happy to march through with bold, unsubstantiated claims. This will likely have the benefit of reaching an audience who are turned off by discussions of male-female differences. But given the mountain of literature in the area, which Seabright samples but does wholeheartedly embrace, he could have more robustly engaged with the positions of others. Seabright rarely names another author and takes them to task, which leaves parts of the book some distance from the cutting edge of debate.

The two most interesting chapters of the book relate to networking and charm. Men tend to have larger networks, and when it comes to positions of power such as top executive positions, those larger networks give men a material return. Seabright also considers that technological progress is raising the need for charm. When the internet can pull in thousands of responses to a job advertisement, it takes something special to get on the shortlist for that job – and networks and charm are an important part of that. Seabright hypothesises that when women take time out of the workforce to have children, their networks suffer as they are no longer on the charm offensive. When they return, everyone who remained in the workforce was busy building and strengthening networks that the woman now no longer has.

Once he has fingered networks as being a factor in the disparate economic outcomes, Seabright puts forward two ideas to address them. His first is that short lists for positions should be subject to quotas. This brings women into the mix for consideration when their networks may not get them through the first cut. They are then assessed on merit against the other short-listed candidates. If networks, not talent, are standing in the way of higher female representation, this may present a solution. However, as Seabright notes, if this is a good idea, companies should do this without any push from outside as it would be in their own interest to find the most talented staff. The other question is what happens to less social but talented men, who Seabright notes often suffer the same penalties from non-conformist life choices.

Seabright’s other idea, compulsory paternity leave, is likely to be the more controversial. Seabright proposes that men should have to take the same breaks as women, which should then remove the signalling and networking cost to women of taking time off work.

Beyond my natural apprehension at a compulsory scheme of that nature, the question at the forefront of my mind was whether networks have merit in themselves. Employers care about signalling as it contains information. And within a job, networks can lead to sales, a real benefit to the employer.

Apart from his policy recommendations, Seabright’s closing chapter has an interesting take on “the model relationship”. Given the balance of conflict and cooperation that a relationship entails, Seabright argues that is unreasonable to expect our relationships to be conflict free, consistently loving and free from jealousy. If a politician slips up, it probably says nothing about their ability to manage government. If we slip up, it may not mean that we no longer love our partner. We should not measure others or ourselves against an unrealisable ideal.

Seabright’s assault on the model relationship is interesting, but I am not convinced that recognising its flaws would allow us to escape relationship straight jackets. Evolved preferences, however unreasonable, underlie the expectations of relationships as much as social norms.

From Jared Diamond’s review of Why Nations Fail:

But it’s obvious that good institutions, and the wealth and power that they spawned, did not crop up randomly. For instance, all Western European countries ended up richer and with better institutions than any tropical African country. Big underlying differences led to this divergence of outcomes. Europe has had a long history (of up to nine thousand years) of agriculture based on the world’s most productive crops and domestic animals, both of which were domesticated in and introduced to Europe from the Fertile Crescent, the crescent-shaped region running from the Persian Gulf through southeastern Turkey to Upper Egypt. Agriculture in tropical Africa is only between 1,800 and 5,000 years old and based on less productive domesticated crops and imported animals.

As a result, Europe has had up to four thousand years’ experience of government, complex institutions, and growing national identities, compared to a few centuries or less for all of sub-Saharan Africa. Europe has glaciated fertile soils, reliable summer rainfall, and few tropical diseases; tropical Africa has unglaciated and extensively infertile soils, less reliable rainfall, and many tropical diseases. Within Europe, Britain had the further advantages of being an island rarely at risk from foreign armies, and of fronting on the Atlantic Ocean, which became open after 1492 to overseas trade.

It should be no surprise that countries with those advantages ended up rich and with good institutions, while countries with those disadvantages didn’t. The chain of causation leading slowly from productive agriculture to government, state formation, complex institutions, and wealth involved agriculturally driven population explosions and accumulations of food surpluses, leading in turn to the need for centralized decision-making in societies much too populous for decision-making by face-to-face discussions involving all citizens, and the possibility of using the food surpluses to support kings and their bureaucrats.

The more interesting question is not how institutions support economic growth, but rather why growth promoting institutions arise in some places and not in others. As Diamond notes, there are some strong patterns in this.

There is an interesting podcast on Science Talk titled The Coming Entanglement, with Fred Guterl interviewing Bill Joy, co-founder of Sun Microsystems, and Danny Hillis.

The basic argument by Joy and Hillis is that we are reaching a point where our systems are so entangled (most of the conversation is in terms of technical systems) that no one understands the whole thing. They suggest that we need to get over the fact that there is no expert who understands what is going on.

One example is the Windows Operating System, with no-one understanding the entire code. That contrasts to their earlier days when they could hold an entire operating system code in their heads. Another example they gave was that no one knows what would happen if GPS got turned off.

The consequence of this is that when something goes wrong, we no longer have the ability to step back and determine what went wrong. Each system so dependent on the other that you might not be able to restart one system without the other, so cannot restore two mutually dependent systems.

Unlike Y2K, which they (not sure which of the two said this) were optimistic about, the entanglement has moved far beyond the level of complication that existed at that time.

This sounds somewhat like the concept of normal accidents, whereby complex systems will fail. The solution does not lie in preventing accidents, but in decoupling from that system so that the collateral damage is minimised when it surely fails.

From an excellent article in Nature News by Ed Yong on problems with replication in psychology:

One reason for the excess in positive results for psychology is an emphasis on “slightly freak-show-ish” results, says Chris Chambers, an experimental psychologist at Cardiff University, UK. “High-impact journals often regard psychology as a sort of parlour-trick area,” he says. Results need to be exciting, eye-catching, even implausible. Simmons says that the blame lies partly in the review process. “When we review papers, we’re often making authors prove that their findings are novel or interesting,” he says. “We’re not often making them prove that their findings are true.”

I recommend reading the whole article.

At the recent The Biological Basis of Preferences and Behaviour conference, Colin Camerer presented the results of a paper about work he and his co-authors had done on chimpanzees at the Primate Research Institute at Kyoto University.

At the beginning of the presentation, Camerer showed a couple of videos of experiments dealing with the working memories of chimps. The videos show subjects undergoing a test in which they see five numbers briefly flash on a screen before the numbers are covered with white boxes. The subject must then press the boxes in the order of the numerals. Of the three videos below, the first is a human subject, the second and third a chimpanzee. The chimpanzee (Ayumu) is receiving pieces of apple for each correct answer, which he is collecting from the lower right of the screen.

While the contrast between the first two videos is striking, the third video shows the power of the snapshot that Ayumu has in his mind.

More on this work can be found on the PRI website and in Current Biology. I’ll post on the substance of the paper presented by Camerer, about the game theoretic abilities of chimpanzees, when it is published (hopefully) soon.

Human

Chimp

Distracted chimp

*Jeff Ely beat me to putting up these videos over at Cheap Talk, but since I already had the post put together, it’s still worth a share.