I'd really like a link to the biracial & white vs. black mothers study if anyone has it.
This is from Rushton and Jensen (2005).
It also addresses a little bit the admixture issue versus using "the old social theory of race".
In the Minnesota Transracial Adoption Study, the IQs of the mixed-race
(Black/White) adoptees averaged between those of the “nonmixed” White and the
“nonmixed” Black adoptees, as expected under a genetic hypothesis (see Table 2).
Results from some other types of studies are also consistent with that hypothesis.
In her review, Shuey (1966) found that in 16 of 18 studies in which skin color
could be used as a proxy for amount of admixture, Blacks with lighter skin color
averaged higher scores than those with darker skin, although the magnitude of the
association was quite low (r .10). The Black American average IQ of 85 (15
points higher than the sub-Saharan African average of 70; see Section 3) is also
consistent with the genetic hypothesis, given the approximately 20% White
admixture of Black Americans (Chakraborty, Kamboh, Nwankwo, & Ferrell,
1992; Parra et al., 1998). The mixed-race “Colored” population of South Africa
also has an average IQ of 85, intermediate to the respective African and White
means of 70 and 100 (Owen, 1992). Early studies of brain weight data also fit with
the genetic hypothesis. Bean (1906) found, as did Pearl (1934), that the greater the
amount of White admixture (judged independently from skin color), the higher the
mean brain weight at autopsy in Black groups. More recent data of this nature are
not available.
***
Although the studies of racial hybrids are generally consistent with the genetic
hypothesis, to date they are not conclusive. It may be true, for example, that
lighter skinned Cape Coloreds and African Americans have better nutrition, have
greater opportunities for learning, or are treated better by their societies. On the
other hand, the Minnesota Transracial Adoption Study (Table 2) held many such
factors constant and removed the most frequently proposed causal agents such as
poverty, malnutrition, poor schools, and dysfunctional neighborhoods. Yet, here
too, the mixed-race children had a higher mean IQ than did the children of two
Black parents, and the means for each group were very similar to those for their
respective counterparts elsewhere in the United States. The discussion in this
section is particularly supportive of Loehlin’s (2000) conclusion that “Research
using larger samples and better techniques for estimating ancestry is called for and
quite feasible” (p. 188).
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