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

Physical Environment and Mental Development 347
ancestral gene pools of the fetus. In two all-white samples from a
New England population, comprising all socioeconomic levels,
Bresler established highly significant relationships among three
factors: fetal loss, the number of countries in the background of
parents, and the distances between birthplaces of parents. The
ancestry of each fetus, whether lost or live-born, was determined
back as far as the great-grandparental generation. Since there are
eight great-grandparents, they could have been born in anywhere
from one to eight different countries. Bresler determined percentage
of fetal loss as a function of the number of different countries
among the birthplaces of the great-grandparental generation. He
also determined the percentage of fetal loss as a joint function of
number of countries among the great-grandparents and the distance
apart (in miles) of the birthplaces of the two parents of the
fetus. Both of these factors serve as indices of the degree of genetic
heterogeneity of the fetus’s ancestry. Bresler’s summary of his
main findings was as follows:
Data on two white populations show that fetal loss (Fx generation)
in matings of the parental generation (P J increases
cumulatively by approximately 2-5 percent to 3 percent with
each additional country of birth in the great-grandparental
generation (Px). A dependent relation shows that increased fetal
loss is also related to greater distances between birthplaces of
mates within the Px generation. Conversely, low fetal loss is
encountered with a small number of countries in the background
and shorter distance between birthplaces. It is suggested that a
large number of countries of birth represents a larger number
of Mendelian gene pools and that with increased mixture of
these gene pools, fetal loss increases proportionately. An animal
model is cited in support of this contention, (p. 24)
Bresler also found that SES had no significant relationship to
percentage of fetal loss in these samples. He specifically excluded
from his study all families in which one or more persons had any
African background in the family history, and he states, ‘No
extrapolation of these findings can be made to interracial matings
at this time.’ So the findings, which are highly reliable, and the
genetic theory that explains them, can serve only to suggest an
hypothesis that the high rate of fetal loss and the various sublethal
aspects of reproductive casualty which are a part of this continuum