The first two articles of this series have covered a brief overview of evolutionary psychology and the difficulty in defining and measuring intelligence. In the first article, I covered that we can measure what people prefer and value, but we don’t know the "why" behind those preferences and values.

An evolutionary psychologist from the London School of Economics, Satoshi Kanazawa, wrote a paper on the origin of individual values and preferences that suggests values are tied to IQ, and you can theoretically predict the values of a nation based on its average intelligence.

The second article dealt with the thorny issue of intelligence – what is it? Can we measure it? Can we predict it using tools we have today? In a general sense, animal intelligence may be defined as the degree of mental or behavioral flexibility resulting in novel solutions. A possible measurement of this flexibility is the efficiency of brain structural organization – the number of cortical neurons, their ability to process data, and the speed at which they process information could be tied to what we consider "intelligence."

In this article, I will hopefully be able to address the many excellent comments from readers on the first two articles, as well as suggest a hypothesis described by Kanazawa as a possible explanation for individual values and preferences (tied to IQ), and how that ties in to the evolution of the human brain and intelligence. Kanazawa was kind enough to respond to an email I sent him with some of the comments, and I will include his responses as well.

The Savanna-IQ Interaction Hypothesis

As described in the first article, Kanazawa’s Savanna Principle says that the human brain has difficulty comprehending and dealing with entities and situations that did not exist in the ancestral environment.

In the ancestral environment there were recurrent adaptive problems, and evolution had "already done all the thinking, so to speak, and equipped the human brain with the appropriate psychological mechanisms," Kanazawa suggests.

This is what I would define loosely as what Gerhard called the "off-brain" storage, or culmination of centuries of knowledge that has become part of the social collective; or, related to what Josh says, adaptive knowledge.

But there had to be occasional problems popping up, Kanazawa said, that were not recurrent and were novel enough that our ancestors had to think and reason in order to solve.

"To the extent that these evolutionarily novel, non-recurrent problems happened frequently enough in the ancestral environment (different problem each time) and had serious enough consequences for survival and reproduction, then any genetic mutation that allowed its carriers to think and reason would have been selected for, and what we now call 'general intelligence' could have evolved as a domain-specific adaptation for the domain of evolutionarily novel, non-recurrent problems."
So how does the idea of general intelligence tie in with the Savanna Principle? Kanazawa says the logical conjunction is the Savanna-IQ Interaction Hypothesis: if general intelligence evolved to deal with evolutionarily novel problems, then the human brain’s difficulty in comprehending and dealing with entities and situations that did not exist in the ancestral environment should interact with general intelligence, such that the Savanna Principle holds stronger among less intelligence individuals than among more intelligence individuals.

In other words, more intelligent individuals should be better able to comprehend and deal with evolutionarily novel entities and situations than less intelligent individuals, but both can deal equally well with evolutionarily familiar values (since these adaptations have been "hard-wired" by evolution). Kanazawa gave a few examples of these novel experiences:

1. The lightning has struck a tree near the camp and set it on fire. The fire is now spreading to the dry underbrush. What should I do? How could I stop the spread of the fire? How could I and my family escape it? (Since lightning never strikes the same place twice, this is guaranteed to be a non-recurrent problem.)
2. We are in the middle of the severest drought in a hundred years. Nuts and berries at our normal places of gathering, which are usually plentiful, are not growing at all, and animals are scarce as well. We are running out of food because none of our normal sources of food are working. What else can we eat? What else is safe to eat? How else can we procure food?
3. A flash flood has caused the river to swell to several times its normal width, and I am trapped on one side of it while my entire band is on the other side. It is imperative that I rejoin them soon. How could I cross the rapid river? Should I walk across it? Or should I construct some sort of buoyant vehicle to use to get across it? If so, what kind of material should I use? Wood? Stones?

When considering values then, you can extrapolate and say that more intelligent individuals may be more likely to acquire and espouse evolutionarily novel preferences and values than less intelligent individuals, while general intelligence may make no difference for the acquisition and espousal of evolutionarily familiar values.

What are these values? Evolutionarily novel values include (but are not limited to) liberalism, atheism, sexual exclusivity (for men), vegetarianism, and democracy. Familiar values include children, marriage, family, and friends.

Before I go on I also want to differentiate between evolutionarily novel and experientially novel – the former is something that did not exist in the ancestral environment, whereas the latter is something that an individual person hasn’t experienced in his or her lifetime. In this series, we’re referring to the former.


Kanazawa uses the contemporary American definition of liberalism: the concern for the welfare of genetically unrelated others and the willingness to contribute large proportions of private resources for the welfare of such others. (He does not use this to mean Democrat versus Republican, in the sense of the parties’ platforms, but simply concern for the welfare of others. People in either party can have concern for the welfare of others.)

Humans are designed to be altruistic toward their genetic kin, repeated exchange partners, tribe/group –our ancestors lived mostly in small bands of 50-150 people. It follows, then, that our mega cities and nations, filled with complete strangers whom we are not likely ever to meet or exchange with, are novel. Liberalism is the concern for the welfare of those millions of strangers – contributing toward government and social programs – something our ancestors didn’t have to deal with given their environment. The Savanna-IQ Interaction Hypothesis predicts that more intelligent individuals are more likely to espouse liberal political ideology than less intelligent individuals.

As an aside, and in response to one of Gerhard’s comments that very little of what we have learned is a result of direct parental education, Kanazawa notes that political attitude has the heritability of 0.65, and about 43% of the variance in political attitudes is determined by genes. Parental socialization is responsible for roughly 22% of the variance, he says, but this did not take into account intelligence, and intelligence is tied to openness to experience (which is negatively correlated with conservatism). A recent study in 2008 showed that more intelligent British children are more likely to become liberal adults.

Back to liberalism: Kanazawa used highest marginal tax rate on individual income as a proxy for contribution toward government and social programs, and income inequality as a measure of the consequence of income redistribution. He found that national IQ has a significantly positive effect on rate of highest marginal individual income tax (p<0.05) and a negative effect on the nation’s net income inequality (p<0.01). Each point in national IQ increases the highest marginal individual tax rate by more than half a percentage point. Example: if we raised the national IQ by 10 points, the highest marginal tax rate increases by more than 5%.


Religion is a cultural universal, but may not be an adaptation in itself – it may have derived from other evolved psychological mechanisms, namely, paranoia. Pretend you’re one of our ancestors, and you’re hanging out near your favorite fruit tree late at night. Suddenly a piece of fruit beans you on the head. You can think one of two things: one, the fruit was intentionally thrown at your head (when in fact it was just because of gravity and the fruit fell on its own – type I error), or two, you were in the wrong place at the wrong time and the fruit just fell (when in fact it was intentionally thrown by a member of an enemy tribe who snuck up on you and wants to hack you to death – type II error).

Of the two thoughts, the second – the type II error, is far more detrimental to survival and reproduction, so it pays to be paranoid – it might save your life. So, evolution should favor psychological mechanisms that result in type 1 errors. As a result, our brains may be more disposed to perceive intentional forces (i.e. the hands of God) behind a wide range of natural phenomena – for example, Greek gods controlled everything from the sun rising to crop cycles. Since this is familiar, the more novel value would be to not believe in an unseen hand, and thus be agnostic or atheistic. And since more intelligent people are predicted to espouse novel values, more intelligent people are predicted to be atheistic.

Kanazawa used three questions to measure religiosity: do you believe in God, how important is God in your life on a scale of 1-10, and independent of whether you go to church would you say you are (a) a religious person, (b) not a religious person, or (c) a convinced atheist. He found that national IQ has a significantly negative effect on the proportion of the population who believes in God (p<0.01), a significantly negative effect on the mean importance of God (p<0.0001), and a significantly negative effect on the proportion who identify themselves as religious (p<0.01). Each point in national IQ decreases the proportion of the population who believes in God by more than a percentage point, and national IQ alone accounts for more than 70% of the variance in the mean importance of God across nations.


Humans have been mildly polygynous throughout human evolution. (N.B. Polygynous is when a man has two or more wives or partners at the same time. Polygamy is when any person has two or more marriage or sexual partners at one time.) This correlates with the spread between size of male and female – the larger the male is compared to the female, the more likely the species is polygynous. Gibbons are the same size, and are monogamous. Gorillas differ greatly in size by gender, and are highly polygynous. In humans, usually the male has had multiple partners while the woman has just had one. This means that sexual exclusivity, monogamy, is novel for males but not for females. More intelligent men, then, would likely espouse monogamy, while less intelligent men are man whores. Kanazawa found that as you may expect, the higher the national IQ, the more monogamous the society (p<0.05).

What does all of this mean?

According to Kanazawa’s data, more intelligent nations tend to be more liberal, atheistic, and monogamous.

But what about the argument that these are more adaptive reasons for psychological behavior, as Josh suggests, as opposed to looking at all the evolutionary forces? Josh says the real null hypothesis should be that psychology is the result of random evolutionary process. I sent this idea, along with some others, to Dr. Kanazawa, and he responded:

I suppose your friend is correct. That evolution has had no effect on the architecture of the human mind is the implicit null hypothesis against which we test our evolutionary psychological hypotheses, although, as the field matures and there remains less and less doubt that the null hypothesis valid, we begin to test competing hypotheses from the evolutionary psychological perspective. Given that the null hypothesis is false and evolution has had an effect on the design of the human mind, which hypothesis is more valid? The null hypothesis your friend proposes has been rejected every single time in the last 17 years!
Mike commented about average intelligence of a species versus the measure of intelligence of individuals in regard to the number of cortical neurons, and I’d direct him to the paper the previous article by Li et al. But regarding the Savanna-IQ Interaction Hypothesis, Kanazawa has a forthcoming paper in the March 2010 issue of Social Psychology Quarterly, which will test the Savanna-IQ Interaction Hypothesis at the individual level.

Simoncito asked about trying to find where cleverness exists in our brains, versus thinking about how intelligence is displayed in behavior. An article by J. Philippe Rushton (Intelligence (2004), 32, 321-328) may be of interest (to simoncito or anyone); it addresses intelligence in an evolutionary framework and the r-K matrix of life history-traits including longevity. Another article of interest, and one that I wanted to tie in to this article but it’s already far too long, is an article in Scientific American on the origins of the left and right brain (July 2009 issue, pages 60-67). This article seems to suggest that the novel evolutionary values described by Kanazawa are under control of the right hemisphere.