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Hereditarian Hypothesis Statement

There has been considerable debate about the representation of human population genetics in a recent book by journalist Nicholas Wade: A Troublesome Inheritance. A letter http://cehg.stanford.edu/letter-from-population-geneticists/signed by 143 scientists, including 16 members of the PLOS Genetics Editorial Board, and PLOS founder Mike Eisen, criticized the book in the New York Times Book Review on August 8, 2014. As there is widespread interest in this issue from our Editorial Board, we have invited Marcus Feldman to publish his book review in PLOS Genetics.

In 1969, Arthur Jensen ignited a decades-long debate when he wrote that it is a “not unreasonable hypothesis that genetic factors are strongly implicated in the average Negro–white intelligence difference” [1]. From this he inferred that educational interventions in communities whose members have lower measured intelligence quotient (IQ) could not succeed.

The errors in Jensen's choice of data [2] and statistical methods used to compute a heritability of about 80% for measured IQ were pointed out by numerous geneticists and statisticians. 25 years after Jensen's incendiary paper, Herrnstein and Murray's book, The Bell Curve[3], drew inferences similar to Jensen's that differences among races and social classes in IQ were genetically based. The Bell Curve elicited a flood of strong criticisms of the data used, the statistical analyses, and the policy inferences [4]. Much of the criticism of Jensen and Herrnstein and Murray centers on their interpretation of heritability of IQ. In 1975, Richard Lewontin and I [5] stressed the failure of the heritability statistic to do what these authors claim; namely, to show that IQ is largely genetically determined and hence that traits related to IQ, such as educational or economic success, would be impervious to environmental intervention.

As pointed out by Nicholas Wade in the first half of A Troublesome Inheritance, we are now in a genomic age, where individual differences at the level of DNA can be detected. The early chapters present a hodgepodge of historical ideas about race, aggression, and genetics. On page 57, Wade gives an inkling of what will come in the last half of the book: “important aspects of human social behavior are shaped by the genes” and “these behavior traits are likely to vary from one race to another, sometimes significantly so” [6].

Whereas inferences on the causes of human behavioral variation referred to above were based on correlations between relatives, on pages 97–99 Wade develops his arguments for the genetic basis of social behaviors in the second half of A Troubled Inheritance from results on worldwide variation in DNA polymorphisms, namely microsatellite polymorphisms (The Rosenberg-Feldman studies) [7], [8] and single nucleotide polymorphisms (another Stanford study) [9], from the Human Genome Diversity Panel [10]. Here, as in his previous journalism about these studies, Wade exhibits a complete lack of understanding of their implications. For example, he does not mention the finding, stressed in both studies, that only 5%–10% of the worldwide genomic variation is between continental groups, while the vast majority is between individuals within populations.

Using data from 15 protein genes, R. C. Lewontin in 1972 [11] was the first to point out that the overwhelming majority of human genotypic variation is within populations, and that continental “races” differed little genetically. 25 years later, Barbujani et al. [12] came to the same conclusion from their study of 109 DNA markers. Wade (page 120) criticizes Lewontin's conclusion that “racial classification is now seen to be of virtually no genetic or taxonomic significance” as representing Lewontin's “political stake in the issue.”

From the data and analyses of worldwide molecular genomic variation, Richard Lewontin and I amplified the conclusions of Lewontin and Barbujani et al. as follows: “The repeated and consistent results on the apportionment of genetic diversity…show that the genes underlying the phenotypic differences used to assign race categories are atypical of the genome in general and are not a reliable index to the amount of genetic differentiation between groups. Thus, racial assignment loses any general biological interest. For the human species, race assignment of individuals does not carry with it any general implication about genetic differentiation” [13]. The increased resolution on patterns of human variation that we now have has enabled us to understand a great deal about human migration, admixture, population size, and natural selection. However, it has not told us that the earlier studies underestimated the biological reality of race.

Even though the between-continent fraction of genetic variation is small, as the reader discovers on leaving the first half of A Troublesome Inheritance, Wade's erroneous interpretation of its significance for racial differences becomes the basis for his entry into the “speculative arena at the interface of history, economics, and human evolution” (page 15). In the second half of the book, he claims that differences among continents in economic development, social institutions, and social behaviors are based in genetics. This classic correlation–causation error cannot be excused on the grounds that Wade is just speculating; continents can be distinguished genetically; they also have different economic and social histories. One cannot conclude, as Wade does, that the former causes the latter.

The first paragraph of chapter seven summarizes Wade's process of inference: “Each of the major civilizations has developed institutions appropriate for its circumstances and survival. But these institutions, though heavily imbued with cultural traditions, rest on a bedrock of genetically shaped human behavior; and when a civilization produces a distinctive set of institutions that endures for many generations, that is the sign of a supporting suite of variations in the genes that influence human social behavior.” I will focus on two of the studies invoked by Wade to justify his totally unfounded claims that differences in the societies of different continents (which he terms “races” even though in a biological sense they are not understood as such) are due to their genetic differences.

The first is by Gregory Clark, an economic historian who studies changes in interpersonal violence, literacy, the propensity to save, and the propensity to work in the English population from 1200 CE to 1800 CE [14]. As Wade puts it on page 154, during this period “the nature of the people had changed.” Between 1200 and 1800, “these behavioral changes in the English population…gradually transformed a violent and undisciplined peasant population into an efficient and productive workforce.” On pages 159–161, Wade explains how this happened. “Clark has uncovered the simple genetic mechanism…the rich had more surviving children than the poor.” And further, “Most children of the rich had to sink in the social scale,” and as a result, “their social descent had the far reaching genetic consequence that they carried with them the same behaviors that had made their parents rich.”

Against the argument that changing culture may have been involved in the 600-year process, Wade states (page 160) that these “behaviors emerged gradually over several centuries, a time course more typical of an evolutionary change than a cultural change.” To justify his claim that 600 years is enough time to have produced “significant changes in social behavior” (page 161) of the English, Wade leans on experiments by Belyaev, who artificially selected silver foxes for tameness. The strength of this selection was extreme: “typically not more than 4 or 5 percent of male offspring and about 20 percent of female offspring have been allowed to breed” [15]. The strongest natural selection on humans is orders of magnitude weaker than this “sufficiently intense” artificial selection imposed on the foxes (page 161). Few evolutionists would agree that 600 years, that is, about 25 generations, is long enough for such significant behavioral changes to be due to human genetic evolution; here and elsewhere in the book, Wade uses “evolutionary” where it is obvious that he means “genetic.” “Ingrained” is another euphemism he occasionally uses. For example, on page 177, “Tribal behavior is more deeply ingrained than are mere cultural prescriptions. Its longevity and stability point strongly to a genetic basis.” Galton and Pearson would have approved of Wade's espousal of a genetic basis for class differences; there is more than a whiff of eugenics here.

Wade devotes almost four pages of chapter seven, the longest chapter in the book, to IQ. After claiming (page 190) that “intelligence is almost certainly under genetic influence,” he goes on to discuss the relationship between wealth and IQ and invokes the work of Richard Lynn and Tatu Vanhanen, in particular their book IQ and Global Inequality[16].

Lynn is known for his work as an associate editor of The Mankind Quarterly, described by the famous psychologist Leon Kamin as a “vulgarly racist” [17] journal. Lynn's 1991 paper on IQ of Africans is described by Kamin as “truly venomous racism, combined with scandalous disregard for scientific objectivity” [17]. In 2002, Lynn wrote the nonsensical statement: “The conclusion that there is a true association between skin color and IQ is consistent with the hypothesis that genetic factors are partly responsible for the black–white difference in intelligence…the evidence that a statistically significant correlation is present confirms the genetic hypothesis” [18]. In placing so much emphasis on Lynn's work (which was strongly supported by the notorious Pioneer Fund, which also supported William Shockley and was chaired by an even more notorious scholar, J. Philippe Rushton), Wade has apparently chosen to ignore important studies on IQ and environment such as those by Brooks–Gunn et al. [19] and Turkheimer et al. [20]. Brooks–Gunn found that “adjustments for economic and social differences in the lives of black and white children all but eliminate differences in the IQ scores between the two groups,” suggesting that socioeconomic status (SES) might be an important contributor to high heritability estimates. In the same vein, Turkheimer et al. found that heritability of IQ depended strongly on SES: there was a high heritability in higher SES environments, but not in low SES environments. By omitting reference to such studies that find very strong environmental contributions to IQ, while focusing on Richard Lynn, the book takes a very hereditarian stance.

Wade gives the appearance (page 192) of care in interpreting Lynn and Vanhanen: “It is hard to know which way the arrow of causality may be pointing, whether higher IQ makes a nation wealthier or whether a wealthy nation enables its citizens to do better on IQ tests.” However, from his statement (page 203) about “the strong heritability of intelligence” and his belief (page 160, referring back to Clark) that in England “the children of the rich carried with them inheritance for the same behaviors that made their parents rich,” we can only assume that Wade believes there is a genetic basis for both IQ and wealth. His “arrow of causality” has two points, with genetics responsible for both IQ and wealth.

This section of the book is redolent of the claims of Jensen, as well as Herrnstein and Murray, mentioned at the beginning of this review. It also harks back to claims by Taubman [21] in the 1970s, based on correlations between relatives, that variation between individuals in wealth has a strong genetic basis. It is most informative to compare Goldberger's 1977 [22] criticism of Taubman's analysis with related negative evaluations of studies on heritability of IQ. By invoking Richard Lynn on racial variation in IQ and wealth, Wade departs from his “speculative arena,” leaving us to infer that he is a devout hereditarian.

Wade goes even further than proposing a genetic basis for continental variation in wealth; he would have us believe that differences in economic and political institutions among populations have a genetic basis. On page 196, he criticizes the book Why Nations Fail by Acemoglu and Robinson [23] because “they have ruled out the obvious possibility that variations in human behavior are the cause of good or bad institutions.” Variation in institutions is why “a part of the world has grown steadily and vastly richer over the past 300 years.” He concludes that a reasonable explanation for this variation “is available in terms of human evolution.”

Wade is using “evolution” here to mean the production and maintenance of genetic differences, and “variations in human behavior” is his euphemism for racial, and hence (in his understanding) genetic differences. He appears to backtrack slightly in the final chapter (pages 240–241), where he poses the paradox “that people as individuals are so similar yet human societies differ so copiously.” His resolution of the paradox is that these societal differences “stem from the quite minor variations in human social behavior…that have evolved within each race during its geographical and historical experience.” Again, “evolved” must be understood in genetic terms: it is “because of their institutions—which are largely cultural edifices resting on a base of genetically shaped social behaviors—that the societies of the West and East Asia are so different.”

We can juxtapose Wade's conclusions on the genetic basis of racial differences in wealth, economies, and institutions with those of Ashraf and Galor on a similar topic. Their claim was that the high and low molecular genetic diversity characteristic of African and Native American populations, respectively, “have been detrimental for the development of these regions,” while “the intermediate levels of diversity associated with European and Asian populations have been conducive for development” [24]. Wade's use of worldwide patterns of human molecular genetic variation to define races and his inference that genetic variation between races explains their economic differences are qualitatively similar to Ashraf and Galor's thesis. Speculation aside, readers of A Troublesome Inheritance are advised to heed the admonition by Guedes et al. concerning Ashraf and Galor: “bold claims on the basis of weak data and methods can have profoundly detrimental social and political effects” [25].

Wade's premise is that molecular population genetics has shown sufficient variation between continents to define races. He argues (page 126) that these genetic differences are responsible for differences in individual social behaviors that “undergird” societal institutions, which themselves differ among races. Ironically, the molecular genomic data that have become available in the last fifteen years—the very data that Wade argues we need to bravely acknowledge—explain in terms of admixture, gene flow, demographic change, etc., why human genetic variation is arrayed the way it is. Echoes of the hereditarian arguments about racial difference in IQ and the reductionist arguments of sociobiology and evolutionary psychology resound in A Troublesome Inheritance. I have no trouble with the existence of human genetic variation. It is Wade's dangerous interpretation, however speculative, of the meaning of human genetic variation that is indeed troublesome.

References

1. Jensen AR (1969) How much can we boost IQ and scholastic achievement. Harv Educ Rev39: 1–123.

2. Kamin LJ (1974) The Science and Politics of IQ. Potomac: Lawrence Erlbaum. [PubMed]

3. Herrnstein RJ, Murray CA (1994) The Bell Curve: Intelligence and Class Structure in American Life. New York: Free Press.

4. Jacoby R, Glauberman N, Herrnstein RJ (1995) The Bell Curve Debate. New York: Times Books.

5. Feldman MW, Lewontin RC (1975) The heritability hang-up. Science190: 1163–1168. [PubMed]

6. Wade N (2014) A Troublesome Inheritance: Genes, Race and Human History. New York: The Penguin Press.

7. Rosenberg NA, Pritchard JK, Cann H, Weber J, Kidd KK, et al. (2002) The genetic structure of human populations. Science298: 2381–2385. [PubMed]

8. Rosenberg NA, Mahajan S, Ramachandran S, Zhao C, Pritchard JK, et al. (2005) Clines, clusters, and the effect of study design on the inference of human population structure. PLoS Genet1: e70. [PMC free article][PubMed]

9. Li JZ, Absher DM, Tang H, Southwick AM, Casto AM, et al. (2008) Worldwide human relationships inferred from genome-wide patterns of variation. Science319: 1100–1104. [PubMed]

10. Cann HM, de Toma C, Cazes L, Legrand MF, Morel V, et al. (2002) A human genome diversity cell line panel. Science296: 261–262. [PubMed]

11. Lewontin RC (1972) The apportionment of human diversity. Evol Biol6: 381–398.

12. Barbujani G, Magagni A, Minch E, Cavalli-Sforza LL (1997) An apportionment of human DNA diversity. Proc Natl Acad Sci U S A94: 4516–4519. [PMC free article][PubMed]

13. Feldman MW, Lewontin RC (2008) Race, ancestry, and medicine. In: Koenig BA, Lee SS, Richardson SS, editors. Revisiting Race in a Genomic Age. New Brunswick: Rutgers University Press.

14. Clark G (2007) A Farewell to Alms: A Brief Economic History of the World. Princeton: Princeton University Press.

15. Trut LN (1999) Early canid domestication: the farm—fox experiment. Am Sci87: 160–169.

16. Lynn R, Vanhanen T (2006) IQ and Global Inequality. Augusta: Washington Summit.

17. Kamin L (1995) Lies, damned lies, and statistics. Jacoby, R., and N. Glauberman, editors. The Bell Curve Debate. New York: Times Books. pp 86.

18. Lynn R (2002) Skin color and intelligence in African Americans: A Reply to Hill. Popul Environ24: 215–218.

19. Brooks-Gunn J, Klebanov PK, Duncan GJ (1996) Ethnic differences in children's intelligence test scores: role of economic deprivation, home environment, and maternal characteristics. Child Dev67: 396–408. [PubMed]

20. Turkheimer E, Haley A, Waldron M, D'Onofrio B, Gottesman II (2003) Socioeconomic status modifies heritability of IQ in young children. Psychol Sci14: 623–628. [PubMed]

21. Taubman P (1976) The determinants of earnings: genetics, family, and other environments: a study of white male twins. Am Econ Rev66: 858–870.

22. Goldberger AS (1977) The genetic determination of income. University of Wisconsin Social Systems Research Institute. Paper 7707.

23. Acemoglu D, Robinson JA (2012) Why Nations Fail: The Origins of Power Prosperity and Poverty. New York: Crown Publishers.

24. Ashraf Q, Galor O (2013) The out—of—Africa hypothesis, human genetic diversity, and comparative economic development. Am Econ Rev103: 1–46. [PMC free article][PubMed]

25. Guedes Jd'A, Bestor TC, Carrasco D, Flad R, Fosse E, et al. (2013) Is poverty in our genes?Current Anthropology54: 71–79.

1800 words

In 2005, Linda Gottfredson published What If the Hereditarian Hypothesis Is True? in the journal Psychology, Public Policy, and Law defending Rushton and Jensen’s (2005) conclusions on the black-white IQ gap. This gap in intelligence between the races has been noticed since the IQ test’s inception 100 years ago. What if the hereditarian hypothesis is true—what if there are genetic differences in intelligence between races? How should society handle such a ‘discovery’ if one were to occur?

In Rushton and Jensen’s opus paper, they didn’t set out to prove that the hereditarian hypothesis is true, rather they set out to prove that the hereditarian hypothesis—which states that 50 percent of racial differences in intelligence come down to genetic factors with environment dictating the other 50 percent—is more tenable the culture-only hypothesis—0 percent genetics 100 percent environment. Gottfredson states that the hereditarian hypothesis becomes scientifically plausible “only after five evidentiary requisites have been met”: “IQ differences among same-race individuals represent (a) real, (b) functionally important, and (c) substantially genetic differences in general intelligence (the g factor), and mean IQ differences between the races likewise reflect (d) real and (e) functionally important differences on the same g factor.” (Gottfredson, 2005: 311) The past one hundred years of intelligence testing has proven all of this. The black-white differences in intelligence are on subtests that are more heritable, proving a genetic component.

The hereditarian hypothesis has been proven by adoption studies such as the Minnesota Transracial Adoption Study, to differences overall in IQ tests, to differences in life success etc. Environmentalists believe it’s ‘racism’ or ‘classism’ that’s the cause for racial/ethnic/class differences in achievement, when a genetic explanation makes a lot more sense.

The Denial of the Hereditarian Hypothesis

The denial of the hereditarian hypothesis has greatly harmed American society. Before the push for multiculturalism in the 60s, a genetic reason for racial/class differences was widely accepted. Minorities couldn’t perform well in school in comparison to whites because they had lower innate g. The difference in causes differences in wealth attainment, salary, mortality, fitness, educational attainment, and other pertinent achievements. This then leads to programs with an abysmal ‘success rate’, such as Head Start. Head Start does not work, its gains fade away in a few years after the program. It’s time to stop Head Start, because it makes people believe that parental intervention can have any kind of effect on a young child, when it’s shown that these so-called gains fade away in a few years as the heritability of intelligence increases. Individuals differ on g, races differ on g, there are differences in achievement and more people in one SES bracket and other people in another SES bracket and it’s down to g. Denying the hereditarian hypothesis wastes taxpayer money as more and more money goes towards programs like Head Start that don’t do anything to close any of the gaps they promise to close.

Academic achievement in math, science, art, humanities, and second language were all shared by the same genes. They found that 60 percent of the results in GCSE scores were attributed to genetic factors. Genes and not upbringing had more of an effect on the scores one receives on the GCSE.

Moreover, other behavioral traits such as psychopathology and personality also account for genetic influence on GCSE scores beyond that predicted by intelligence. This shows that ‘nature’ wins out in the nature-nurture debate. If individual differences in test scores are largely determined by genetics, why not the black-white difference?

Individuals nor groups are ever ‘equal’ in terms of any capacity. One will be better at something than someone else, and that will largely be determined by genetic factors. Training and repetition brings out the best in one that’s genetically inclined to excel. We accept genetic differences for differences in sports, such as sprinting and distance running. They are genetically inclined to excel at those competitions due to fast and slow twitch muscle fibers. Take Usain Bolt. Do you think anyone can train to get to that level? Do you think random Joe can just wake up one day and decide to try to be the fastest man in the world? If you say no, you’re a hereditarian. Of course Bolt’s training makes him better, but without his genetics, he wouldn’t be the fastest man in the world.

Now take the genetic differences from sports (that any sane person would recognize), and think about that in regards to brain power. We are talking about 2 groups that have been genetically isolated for tens of thousands of years. They had to do different things to survive and both faced different selective pressures that would have an effect on intelligence.

The worldwide differences in IQ between East Asians, Europeans and Africans; an inverse correlation between the race differences and brain attributes and black-white-East Asian differences in body maturation; . 2 and .4 correlations with skull size and in vivo brain volume, moderately high correlation of .6 to .7 of different IQ test’s loadings on the magnitude of the black-white-East Asian differences as well as the measures of the subtests being rooted in biological and genetic processes; rising heritability of IQ; differences in crime, gestation, and sex ratio at birth, law-abidingness, marital stability; and a genetic divergence of world population groups during evolution. The most telling one is the last one, genetic divergence of world population groups during evolution. These differences in the brain are rooted in genetic factors. The hereditarian hypothesis fully explains within and between group differences in achievement and intelligence. No “culture-only” hypothesis could ever convince me otherwise.

Richard Nisbett has attempted to say that the hereditarian hypothesis is wrong and that culture-only theory is the only game in town. He couldn’t be more wrong. Citing studies like Moore and Eyferth to make your case against the hereditarian hypothesis won’t get you anywhere. They had a smaller sample size, and some of the subjects were extremely young. Environmentalists use these studies to say that the difference in IQ comes down to a type of ‘ghetto’ environment that saps American blacks’ intellect and that raised away from that type of environment, they’d be able to score on par with  whites. Except that’s not what was found in the Minnesota Transracial Adoption Study. This is the only study to test the children again at age 17, when genetics would be taking its full effect. The racial gap in intelligence still stayed the same (Rushton and Jensen, 2005: 258). I’ve written about the strong evidence for the hereditarian hypothesis in regards to adoption studies and how they support the hypothesis that genetics, and not culture, are the cause for differences in intelligence.

If the Hereditarian Hypothesis is Accepted What Policies Should Change?

If the general public were to ever accept a genetic hypothesis for individual and group differences as a whole, then affirmative action and other such programs that shoehorn kids with lower ability into schools should be abolished and these spots should be filled on merit. Sure there would be fewer blacks and more whites, Jews, Asians, than blacks, ‘Hispanics’ and others but that’s how a merit-based society looks, not one based on feelings and imaginary causes of racism as the culprit for any types of intellectual downfalls. When we come to our senses with genetics and educational achievement and intelligence—which should be coming soon due to the advent of CRISPR—then America can start to become less polarized, in my opinion, on the so-called ‘racist system’ ‘holding down’ minorities. Maybe if people/groups accepted they were less intelligent and it was due majorly to genetic factors, then some of this racial animosity between groups in America will die down. That’s an extremely far reach, though, and I can see them then arguing that accepting by accepting the hereditarian hypothesis then we should continue these programs.

That’s an extremely far reach, though, and I can see them then arguing that accepting by accepting the hereditarian hypothesis then we should continue these programs due to genetic differences. They would say “Well, as a group, we are less inclined to make it into higher areas of learning so we, therefore, should continue to receive these benefits.” To that I would say you’ve been taking advantage of these benefits for 50 years and what’s changed? Billions of dollars have been spent on affirmative action and related cases since the 60s and what has changed? These groups still complain and talk about being oppressed by ‘the man’ not getting what they want. Yet there is an ongoing racial preference for blacks and ‘Hispanics’ over whites and Asians in US medical schools. This is all an effect of affirmative action and the policies it brings to American institutions. Admission into places of higher learning should be completely merit-based, not based on what racial/ethnic group you belong to. That in and of itself is continuing the so-called ‘racism’ and ‘prejudiced attitudes’ that people complain about since they insist on having special privileges based on their ancestral background.

If we were to accept the hereditarian hypothesis as a country, I’d hope to see an abolishment of affirmative action, Head Start, and related programs that do not work. The acceptance of the hereditarian hypothesis would only be a net gain over time, as people would learn to not blame ‘the man’ on their problems, but would look to better themselves in ways that accentuate their strengths. Since any attempt at raising scholastic achievement has failed due to the heritability of intelligence and how it increases as one ages (which is why Head Start doesn’t work and should be abolished) once this is accepted then other avenues can be taken to address these issues that don’t focus on attempting to raise scores. Gottfredson states at the end of her paper that we should have targeted intellectual support for those with an IQ below 80. She also says we should make some jobs less complex, ie “inadequate or overly complex labeling, instructions, and forms”, target training and education towards people with that level of intelligence, and provide more assistance in daily living matters,  This can increase their QoL and ability to attain meaningful employment.

She sees a more positive outlook in the future than I do. I see things become more stratified as automation rolls out. This will have the lower IQ people out of work, while the higher IQ people still are sitting well at the top due to the increasingly complex society that we make for ourselves. Accepting the hereditarian hypothesis can ease this slightly by targeting programs at the less intellectually inclined as well as attempt to soften the claims of ‘racism’ when this starts to really become noticeable. The only way to explain such a disparity is with a genetic hypothesis, at least 50/50 genetics culture. The culture-only theory has no leg to stand on. Once we accept that individual and group differences are due to genetics, then we can begin to accept some of the differences in our society in terms of class and race.

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