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.