Intelligence of the Mother, Temperament and Physical of the Father - although
this concerns humans, I've found that this is pretty much true of dog
breeding also. Not an absolute in dogs as if we are using dog's with a
high COI (inbreeding coefficients) brains and or beauty can be skewed
by the preponderance of fewer ancestors.
Do Children receive their Intelligence from their Mothers?
In an essay in the weekly Lancet medical journal, an Australian
geneticist has recently suggested that relatives and friends may be
getting things backward when they wish a baby the good looks of its
mother and the brains of its father. Or, restated in another way,
smart men may be bright because of genes they inherit from their
mothers. Gillian Turner (1996) of Hunter Genetics in Newcastle,
New South Wales says that a growing body of evidence suggests that
several genes, actually "eight discrete localizations", which determine
intelligence appear to be located on the X chromosome, the chromosome
that men inherit from their mothers. Such localizations or genes
"extend over the short and long arm of
the X chromosome" (p. 1814).
For the purposes of her most informative essay, Turner defined
intelligence "as the ability to deal adaptively with the changing
environment, to benefit from past experiences, to proceed in
goal-directed fashion, to pursue productive avenues of problem solving,
and to perceive common properties in otherwise separate domains of
experience" (p. 1814).
In Turner's own words, "these genes are distributed along the whole
length of the X chromosome and, presumably, code for various anatomical
or functional parts of the neural substratum of intelligence" (p.
1814). That is, women carry the gene for intelligence on their X
chromosome and are solely responsible for passing it on to their sons.
Thus, Turner forewarns men that they should temper hormones with logic
when selecting the mothers of their children and go for brains rather
than for good looks. Similarly, she feels that women are more
able to select their partners for their looks as they could be assured
that brains comes from the female side.
To repeat once again, Turner's argument goes along these lines.
Because the genes for intelligence are on the X chromosome, a single
mutation will have more effect on a man than on a woman. This is
because a woman inherits two X-chromosomes, one from her father and one
from her mother. Therefore, if she inherits a mutant gene on the
X chromosome from one parent, there is a good chance that she
will inherit a normal gene on the X chromosome from the other
parent which will dilute the mutant's impact (see Cooper, 1996; but for
a critical analysis, see Scully, 1996).
However, a male has only one X chromosome, inherited from his
mother. It is paired with the much smaller Y chromosome
from his father. And because the Y chromosome is so small, it
does not have a gene to match every gene found on the X chromosome.
As a result, in a male, a mutant gene on the X chromosome is likely to
be the only such gene and, unopposed, will have its full effect.
Conversely, if the predominate gene is not as strong as it should be,
the man is more likely to suffer mental retardation. Turner's
current hypothesis that if the gene is the one that increases
intelligence, then its full effect will be seen in men, while in women
the benefit is less pronounced.
This explains, she states, why some men are extraordinarily
intelligent. She concludes her two-page article by suggesting to
men that if they want smart sons their best bet is to marry a smart
To summarize, this discovery that women pass on their intelligence gene
to male offspring via the X chromosome is significant for mate
selection. Hence, a woman can choose a brawny mate yet
still be assured of bearing intelligent children since she has an extra
X chromosome. Meanwhile a man's "primitive urges in mate
selection are coded in his genome, and that they target current
ideals of sexual attractiveness and youth" (Turner, 1996, p. 1815).
So if a man wants to have smart sons, Turner concludes, his best chance
is to marry a smart woman, for it appears it is her X chromosome genes
that will determine how bright her boys will be.
Cooper, Glenda, (1996, June 28). Brainy sons owe intelligence to their
mothers. Independent, p. 4.
Scully, Jackie Leach (1996, July 02). Genes don't make us what we are.
Independent, p. 11.
Turner, Gillian (1996, June 29). Intelligence and the X chromosome. The
Lancet, 347(9018), 1814-1815.