Why night owls are more intelligent, Personality and Individual Differences 47 (2009) 685–690.


The origin of values and preferences is an unresolved theoretical problem in social and behavioral sci-
ences. The Savanna–IQ Interaction Hypothesis suggests that more intelligent individuals are more likely
to acquire and espouse evolutionarily novel values and preferences than less intelligent individuals, but
general intelligence has no effect on the acquisition and espousal of evolutionarily familiar values and
preferences. Individuals can often choose their values and preferences even in the face of genetic predis-
position. One example of such choice within genetic constraint is circadian rhythms. Survey of ethnog-
raphies of traditional societies suggests that nocturnal activities were probably rare in the ancestral
environment, so the Hypothesis would predict that more intelligent individuals are more likely to be noc-
turnal than less intelligent individuals. The analysis of the National Longitudinal Study of Adolescent
Health (Add Health) confirms the prediction.

It doesn’t happen often, but i don’t like this evo psych hypothesis. :P I am referring to the Savanna hypothesis.

Choice is not incompatible with or antithetical to genetic influ-
ence. As long as h2 < 1.0, genes merely set a broad reaction range,
and individuals can still exercise some choice within broad genetic
constraints. For example, political scientists have discovered that
two genes are responsible for predisposing individuals to be more
or less likely to vote in elections (Fowler & Dawes, 2008). However,
individuals can still choose to turn out to vote or not for any elec-
tion, and there are environmental (nongenetic) factors that can
predict their voting (Kanazawa, 1998, 2000).

Pretty interesting. The full cite is: Fowler, J. H., & Dawes, C. T. (2008). Two genes predict voter turnout. Journal of Politics, 70, 579–594.

Virtually all species in nature, from single-cell organisms to
mammals, including humans, exhibit a daily cycle of activity called
the circadian rhythm. ‘‘This timekeeping system, or biological
‘‘clock,” allows the organism to anticipate and prepare for the
changes in the physical environment that are associated with day
and night, thereby ensuring that the organism will ‘‘do the right
thing” at the right time of the day” (Vitaterna, Takahashi, & Turek,
2001, p. 85). The circadian rhythmin mammals is regulated by two
clusters of nerve cells called the suprachiasmatic nuclei (SCN) in
the anterior hypothalamus (Klein, Moore, & Reppert, 1991). Genet-
icists have by now identified a set of genes that regulate the SCN
and thus the circadian rhythm among mammals (King & Takahashi,
2000). A behavior genetic study of South Korean twins (n = 977
pairs) shows that heritability in morningness–eveningness is .45
and nonshared environment accounts for 55% of the variance,
while shared environment does not appear to explain any of the
variance in it (Hur, 2007).

Interesting to me on a personal level. Since i appear to have a non-24 circadian rhythm.

In order to ascertain the extent to which our ancestors might
have engaged in nocturnal activities, we have consulted ethno-
graphic records of traditional societies throughout the world. In
the 10-volume compendium The Encyclopedia of World Cultures
(Levinson, 1991–1995), which extensively describes all human cul-
tures known to anthropology, there is no mention of nocturnal
activities in any of the traditional cultures. There are no entries
in the index for ‘‘nocturnal,” ‘‘night,” ‘‘evening,” ‘‘dark(ness),” and
‘‘all-night.” The few references to the ‘‘moon” are all religious, as
in ‘‘moon deity,” ‘‘Mother Moon (deity),” and ‘‘moon worship.”
The only exception is the ‘‘night courting,” which is a socially ap-
proved custom of premarital sex observed among the Danes and
the Finns, which are entirely western cultures far outside of the
ancestral environment.

What. Never heard of this. Googled it and found this:

Marriage. Women married into the circumstances of their grooms, whether landed or landless. Property owners tended to arrange marriages for their sons and daughters so that the young couple could have a farm of their own. Marriage was neolocal insofar as newlyweds usually set up housekeeping on their own. A patrilocal quality was imparted, however, by the tendency to settle in the community of the groom’s family or even to take over the farm of the groom’s parents. Divorce was difficult to obtain legally and was strongly censured by village opinion and church morality. Adultery in the village was regarded as highly reprehensible. Unmarried mothers were ostracized. A woman encountered no difficulty, However, if a pregnancy occurred before marriage but in betrothal, especially when a gold ring had been given to the young woman. Many couples hitherto only casually joined saved the situation when a pregnancy occurred by announcing that they were engaged. Premarital sexual activity was, in fact, common, and young men in many villages were permitted to sleep over in the bed of a young woman in the custom called night courting. Village customs thus set the stage for the Sexual freedom and independence of both women and men that is characteristic of Denmark today.

Seems to be an older cultural thing.


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