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Savanna-IQ interaction hypothesis

Author: Dr Simon Moss


The basic contention of the Savanna-IQ interaction hypothesis is that intelligent individuals tend to flourish on tasks that are novel--tasks that diverge considerably from the activities that humans have undertaken throughout their evolutionary history (Kanazawa, 2004, 2008;; Kanazawa & Perina, 2009). This contention emerges from two key premises.

According to the first premise, derived from the field of evolutionary psychology, the human brain primarily evolved to accommodate the conditions that were pervasive during a previous epoch (e.g., Cosmides, 1989;; Cosmides & Tooby, 1989;; Crawford, 1993;; Tooby & Cosmides, 1990;; Tooby, Cosmides, & Price, 2006). Many cognitive mechanisms evolved to facilitate key tasks at the time, such as foraging (Rode, Cosmides, Hell, & Tooby, 1999). As a consequence, the human brain may not be optimal to withstand the complexities of society today.

Specifically, the human brain primarily evolved while humans negotiated the African savanna, during the Pleistocene Epoch. To clarify, geological time tends to be divided into various units, such as supereons, the largest unit, eons, eras, periods, epochs, and ages, the smallest unit. To illustrate, Triassic, Jurassic, Cretaceous, Paleogene, and Neogene are all periods. The latest period, Neogene, entails the Miocene, Pliocene, Pleistocene, and Holocene epochs. The Pleistocene epoch, which spanned from approximately 2.5 million years ago to 130,000 years ago, witnessed the evolution of man.

According to the second premise, mechanisms evolved that enable humans to solve problems that diverged from the tasks that epitomized the Pleistocene epoch. These mechanisms, collectively, represent general intelligence.

Taken together, these premises imply that general intelligence might not be needed to resolve problems or undertake tasks that mirror the activities that humans completed during the Pleistocene epoch. In contrast, general intelligence does enhance performance on tasks that are touted as evolutionary novel.

Empirical evidence

Nocturnal activities

Several studies have accumulated evidence that substantiate the Savanna-IQ interaction hypothesis. Kanazawa and Perina (2009) contended, and then verified, that intelligent individuals are more inclined to flourish at night. Specifically, humans evolved to be diurnal--to restrict most of their activities to the day rather than to the night.

Many arguments reinforce the proposition that humans, throughout evolution, tend to be active mainly in the day. First, humans rely appreciably on their vision--a sensory modality that is not especially effective at night, particularly before the advent of artificial light. Second, in almost all traditional cultures, as emphasized by a vast array of ethnographies, activity begins at dawn and tends to wane at dusk. This pattern, for example, has been observed in the Yanomano, the Mukogodo, the !Kung San, and the Sacha Runa (for a brief review, see Kanazawa & Perina, 2009).

Accordingly, the modern trend to udnertake some activity in the night, a trend that was facilitated by artificial lighting, demands intelligence. That is, according to the Savanna-IQ interaction hypothesis, general intelligence is needed to complete tasks that diverged from the ubiquitous activities in a previous epoch. General intelligence, therefore, should be correlated with willingness to maintain activity during the night.

To assess this possibility, high school students completed a test of verbal intelligence, the Peabody Picture Vocabulary Test. In addition, participants were asked to estimate the time they usually retire to bed on both school days and weekends. Consistent with the Savanna-IQ interaction hypothesis, students who performed well on the test of verbal intelligence also typically retired to bed late (Kanazawa & Perina, 2009).

Alternative explanations for nocturnal activities

Nevertheless, alternative explanations could, potentially, explain the relationship between general intelligence and activity during the night. Specifically, many other factors affect the circadian preferences of individuals, sometimes called morning versus evening types.

Diaz-Morales (2007), for example, showed that personality is related to whether individuals are alert, energetic, and capable during the morning or night. Specifically, individuals who prefer the night tend to be less conscientious. They also utilize logical rational arguments, in lieu of their intuition, to reach decisions. Finally, they prefer tangible information rather than abstract concepts.

Several mechanisms could explain the association between personality and activity during the night. To illustrate, the body clock of humans naturally spans 24 hours. That is, if humans lived in a cave, with no interaction with anyone else, they would awake 1 hour later each day. As a consequence, all humans experience a natural tendency to want to awake later each morning. Conscientious individuals, however, are especially likely to conform to social conventions. That is, they override their natural impulses more effectively and, as a consequence, can more easily awake earlier.

In short, individuals who are conscientious, and also neglect their intuitions, are more alert in the morning than in the evening. These qualities, however, might hinder intelligence, at least on some tasks (see Cognitive experiential self theory).

Intelligence across nations

According to Savanna-IQ interaction hypothesis, national intelligence should be elevated in nations that are remote from sub Saharan Africa. That is, novel features--that is, features that differ from the contexts that humans experienced during the Pleistocene Epoch in sub Saharan Africa--are more common in nations that are significantly distant from this region.

Consistent with this possibility, national IQ is positively associated with latitude (Kanazawa, 2008). Nevertheless, this association can be ascribed to the notion that IQ increases as temperature diminishes, because individuals need to develop the capacity to adapt to cold conditions.

However, Kanazawa (2008) also showed that IQ is positively associated with longitudinal distance from sub Saharan Africa. Such distance tends to be inversely related to temperature. This finding, therefore, seems to align to the Savanna-IQ interaction hypothesis.

Other theories of general intelligence

The capacity to adapt to stress

Bates (2007) reviewed various studies that indicate that g, or general intelligence, may reflect an index of the extent to which the developmental processes of individuals can adapt suitably to stresses in the environment. Specifically, some individuals possess alleles that enhance their capacity to adapt in response to stresses, such as relentless demands or food deprivation. These adaptations enhance a vast array of physiological processes and, ultimately, manifest as intelligence. In contrast, some individuals possess fewer of these alleles and, therefore, do not adapt as effectively.

This premise can explain a vital observation: Intelligence is correlated significantly with physical characteristics. To illustrate, in one study, Bates (2007) measured the extent to which the body parts of individuals--the length of their fingers, the width of their ankles and elbows, as well as the height of their ears--are asymmetrical. If body parts were asymmetrical, individuals did not perform as well on an abstract intelligence test, the Raven's progressive matrices. Furthermore, head size mediated this relationship.

According to Bates (2007), these body parts are usually symmetrical. Asymmetries imply that development could not withstand stress, called development instability. That is, individuals could not adapt to stress effectively. This adaptation also compromises the capacity of individuals to solve problems, manifesting as limited intelligence. Brain size also reflects both this capacity to adapt and correlates with general intelligence.

Allocation of talent in society

As Strenze (2013) showed, not only does IQ differ across nations, but the extent to which people with the highest IQ are allocated to the most complex jobs also varies. Indeed, in nations in which people with high IQs are assigned to complex jobs, economic development tends to be more pronounced.

Strenze (2013) developed a series of indices that measure this allocation of talent. Measures included the relationship between education and wages, the relationship between ability and wage or occupation--such as manager, professional, or clerical worker--the prevalence of use in ability tests, and finally the association between job complexity and wages. Most of these measures, besides the prevalence of ability tests or association between education and wages, were positively associated with growth in GDP, especially in wealthier societies. Accordingly, an efficient allocation of talent, in which individuals with advanced capabilities are not wasted in jobs where these talents are not utilized, facilitates economic development.


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Last Update: 7/4/2016