Girls Mature Earlier Than Boys, but Boys Become More Intelligent; Cause May Be Evolutionary Legacy of Polygyny

A longitudinal study of sex differences in intelligence at ages 7, 11 and 16 years
Richard Lynn a,⇑, Satoshi Kanazawa b

a b s t r a c t
This paper presents the results of a longitudinal study of sex differences in intelligence as a test of Lynn’s (1994) hypothesis that from the age of 16 years males develop higher average intelligence than females. The results show that at the ages of 7 and 11 years girls have an IQ advantage of approximately 1 IQ point, but at the age of 16 years this changes in the same boys and girls to an IQ advantage of 1.8 IQ points for boys.

From the discussion:

It is an interesting question why girls mature earlier than boys.
One reason may be in human evolutionary history of mild polygyny.
Under polygyny, girls who reach puberty earlier gain a reproductive
advantage over their age mates by being able to marry
polygynous men. The reason for this is that females are in competition
with other females for reproductive success. Females who
mature earlier than other females can start reproducing earlier
and have access to polygynous men, while their age mates who
have not yet reached puberty cannot. At the same time, there is
no reproductive incentive for men in a polygynous breeding system
to mature earlier. Another possible reason for the earlier maturation
of girls than boys is that decline in gamete quality with age
is a more serious constraint for women than for men. Decline in
sperm quality is buffered by the large number of sperm produced.
In contrast, ova production is much more limited. Women are
therefore under stronger selection pressure to begin mating as
soon as possible.

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3 comments
bgc says November 9, 2011

Richard Lynn has been saying this for many years, but few have been listening. From Lynn’s other work, the Male IQ advantage at 18 would be expected to have increased still further than at 16.

Reply
al fin says November 16, 2011

Maturing early can have its costs. Look at the earlier physical maturing of black babies, and the difference in lifespan.

We need to be very careful when comparing IQ scores of different groups of children. The differential in maturity level in different groups can paint a deceptive picture.

This is no doubt one reason why the IQ of blacks seems to decrease with aging out of childhood. The headstart in early maturation eventually gives way to the later and greater development of non-blacks.

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    anton says August 10, 2016

    Africans dont mature earlier as babies or reach pubety earlier.
    Maybe african americans, but tgat is another topic.
    Anyway, nobody was talking about blacks in the article.

    Reply
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