Bell Curve

3 10 The National Context Ethnic Differences in Cognitive Ability 3 11A follow-up a decade later, with the children in adolescence, doesnot favor the no-genetics case."5 The new ordering of IQ means was109 for the biological children of white parents, 106 for the white adoptivechildren, 99 for the adopted children with one black parent, and89 for the adopted children with two black parents."261 The mean of 89for adopted children with two black parents was slightly above the nationalblack mean but not above the black mean for the North CentralUnited States. The bottom line is that the gap between the adoptedchildren with two black parents and the adopted children with twowhite parents was seventeen points, in line with the B/W difference customarilyobserved. Whatever the environmental impact may have been,it cannot have been large.Scarr and Weinberg continue to argue that the results are consistentwith some form of mixed gene and environmental source of the B/Wdifference, which seems to us the most plausible concl~sion.'~~ Butwhatever the final consensus about the data may be, the debate over theMinnesota transracial adoption study has shifted from an argumentabout whether the environment explains all or just some of the B/Wdifference to an argument about whether it explains more than a trivialpart of the difference.Several smaller studies bearing on racial ancestry and IQ were wellsummarized almost two decades ago by Loehlin, Lindzey, and Spuhler.L2yThey found the balance of evidence tipped toward some sort of mixedgene-environment explanation of the B/W difference without sayinghow much of the difference is genetic and how much en~ironmental."~"'This also echoes the results of Snyderman and Rothman's survey of contemporaryspecialists.The German StoryOne of the intriguing studies arguing against a large genetic component toIQ differences came about thanks to the Allied occupation of Germanyfollowing World War 11, when about 4,000 illegitimate children of mixedracial origin were born to German women. A German researcher trackeddown 264 children of black servicemen and constructed a comparisongroup of 83 illegitimate offspring of white occupation troops. The resultsshowed no overall difference in average IQ.'" The actual IQs of the fatherswere unknown, and therefore a variety of selection factors cannot heruled out. The study is inconclusive but certainly consistent with the suggestionthat the B/W difference is largely environmental.But dissenting voices can be heard in the academic world. For example,a well-known book, Not in Our Genes, by geneticist RichardLewontin and psychologists Steven Rose and Leon Kamin, criticizesanyone who even suggests that there may be a genetic component tothe B/W difference or who reads the data as we do, as tipping toward amixture of genetic and environmental influences.I3' How can they dothis? Mostly by emphasizing those aspects of the data that suggest environmentalinfluences, such as the correlations between the adoptingparents' IQs or educational levels and the IQs of their black adoptedchildren in the Minnesota study from the first follow-up (the book waspublished before the second follow-up). But they have nothing to sayabout the aspects that are consistent with genetic influence, such as theeven larger correlations between the educational level of either the biologicalmothers or fathers and the IQs of their adopted-away black children."'Although Lewontin, Rose, and Kamin do not say it in so manywords, their argument makes sense if it is directed at the claim that theB/W difference is entirely genetic. It does little to elucidate the ongoingscientific inquiry into whether the difference has a genetic component.We have touched on only the highlights of the arguments on both sidesof the genetic issue. One main topic we have left untouched involvesthe malleability of intelligence, with two extremes of thought: that intelligenceis remarkably unmalleable, which undercuts environmentalarguments in general and cultural ones in particular, and that intelligenceis highly malleable, supporting those same arguments. Becausethe malleability of intelligence is so critical a policy issue, it deserves achapter of its own (Chapter 17).RETHINKING ETHNIC DIFFERENCESIf the reader is now convinced that either the genetic or environmentalexplanation has won out to the exclusion of the other, we have notdone a sufficiently good job of presenting one side or the other. It seemshighly likely to us that both genes and the environment have somethingto do with racial differences. What might the mix be? We are resolutelyagnostic on that issue; as far as we can determine, the evidence does notyet justify an estimate.We are not so naive to think that making such statements will domuch good. People find it next to impossible to treat ethnic differences