Synopses & Reviews
The author presents a theory that major genes controlling the growth of human intelligence, both left- and right-brain attributes, are on the X-chromosome. The more significant of the implications of such X-linkage include: - Males tend to be more variable in intelligence. - Partial or total reversions to the aboriginal level of intelligence can account for virtually all cases of non-specific mental subnormality. - Since the X-linked genes control a pattern of growth, boys are more variable in the age of readiness for the skills required for progress in school. - Being on the X-chromosome, these genes, favorable or unfavorable, are not passed on from father to son, although they are passed on from father to daughter. In effect, earlier studies have come up with estimates of the heritability of intelligence that are too low.
Theorizes that the great variability in male intelligence is linked to the X chromosome and presents an evolutionary theory that is based on the belief that intelligence is passed from mother to son and not from father to son.
Table of Contents
The Big Leap
In Other Words
Chromosomes, Especially X
Variability in Intelligence
Division of Labor Within the Brain
Natural and Sexual Selection
The Races and the Spread of Homo Sapiens
Other X-Linked Traits
X-Linked Mental Deficiency
X-Linkage and Learning Disorders
Inheritance of X-Linked Traits
Sex Differences in Variance
Editorial Comment: What Good Is All This?