Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

226 Educability and Group Differences
group; since these alternate forms occupy the same locus and are
therefore mutually exclusive, he will not possess G2 or G3. So,
for this individual, G 'l = 1 and G'2 = G'3 = 0. This individual,
then, is represented in the top right-hand cell (b PAGl) of the above
matrix. The estimated probability E(b') that this individual’s G 'l
blood type originated from Caucasian ancestors is thus:
M P
E(b') = --------------- ^ 4 ------- (9.2)
MPAGl+ (l-M )P CGl
where P is the value shown in the first table above and M is the
proportion of Caucasian genes in the hybrid group, being the
average of a number of determinations using blood groups for
which the estimated ancestral frequencies are most reliable, such
as the Duffy Fya gene. For each individual E(b') is determined
similarly from a number of polymorphisms, mostly various blood
antigens, and an average of the Vs, b \ will be the estimate of the
proportion of Caucasian genes in an individual. Since there is
non-random mating in natural populations, there should be a
correlation between individual estimates of b' for various genes;
that is, because of assortative mating, genes of Caucasian origin
would have tended to stay together to some greater than chance
degree in the Negro hybrids. The extent of this deviation from
random assortment can be computed. If it can be shown that the
value of b' for one assessed phenotypic character (e.g., a particular
blood group) can reliably predict the average b' for all the other
assessed phenotypes, then it can be presumed that it also predicts
the genetic mix in the unassessed phenotypes. If the estimates of
b' for individuals meet these criteria with a high level of statistical
significance, the b's for individuals can be correlated with measures
of skin color and of mental ability. If the correlation of b' with
intelligence is significantly larger than with skin color (or if the
partial correlation of b' and IQ, with the effect of skin color
removed, is significantly greater than zero) we would reject the
hypothesis of no genetic racial difference in ability.
Since variation in skin pigmentation, because of its socialenvironmental
consequences, is controlled in this research design,
any direct biochemical connection between degree of skin pigmentation
and intelligence must be either ruled out or, if such a
relationship is established, its consequences for the present design
must be assessed. The possibility of a biochemical connection