Personal genomics: “measures of intelligence”
Posted by Nathaniel Comfort on 09/09 at 07:19 AM
A recent blog post by the genetic counselor Robert Resta mentioned a client who patronized a direct-to-consumer (DTC) genomics company to learn about her disease risk. In the results she received, tucked in among the estimated risk for breast cancer and curly hair, was a result that set Bob’s and my historical radar a-flashing: “measures of intelligence.”
The company, 23andMe, is one of the leaders in the marketization of genetic information. They offer, for several hundred dollars, profiles of genealogy or health information (mostly disease risks) based on genetic markers in the DNA in your spit, which you send to them in a little tube.
But intelligence is not a health risk for anyone with the wherewithal to use DTC genomic profiling. Measuring it is genetic tourism. And by including it in their panel of tests, 23andMe is exposing a long-discredited cultural and intellectual legacy.
In the accompanying marketing text on their website, 23andMe appears to be the picture of circumspection. “Though genetics clearly plays a role, the relative significance of nature and nurture in determining a person’s intelligence is highly controversial,” they write. “Even the nature of intelligence and the validity of tools used to measure it are subject to great debate.” However, they conclude with hard numbers: “Recent studies estimate that in early childhood about 25 - 40% of individual variation in measurable intelligence can be attributed to genetics. In adults, this number increases to about 80%.”
First, IQ is not “intelligence.” We’ll get to the relationship between the two in a moment, but just note the slippage there.
Second, there’s a history to that 80%. In 1994, just as the Human Genome Project was getting off the ground, John Murray and Richard Herrnstein published the now-infamous book The Bell Curve. The core of its 900 pages was the argument that although it may be politically incorrect to say it, intelligence is real, IQ tests measure it, it’s about 80% heritable—and it’s correlated with race.
It was an old argument. Herrnstein himself had been making it since 1971, in a much-cited article in The Atlantic titled, “IQ.” The Berkeley psychologist Arthur Jensen developed it in a 1969 article in the Harvard Educational Review—whose 120 turgid pages bore the blustery stylistic hallmarks of this literature. All three leaned on the early 20th century work of the English psychologist Cyril Burt, and all depend on the association of IQ with Spearman’s “g”, for general intelligence. 23andMe calls it “nonverbal IQ.” The roots of this go way back, to early eugenicists such as Edward Thorndike and Francis Galton.
But let’s stick with Jensen, because he developed a genetic argument that is most relevant to the 23andMe test. Jensen’s argument was that since blacks characteristically score lower than whites on IQ tests, and since IQ is highly heritable and therefore innate and unchangeable (Jensen estimated the heritability of IQ at 80%—the number preferred by 23andMe), there is no point in wasting national resources on compensatory education to raise black students to the level of whites. We should, instead, train them in jobs that are their lot in life, as dictated by their highly heritable IQs.
What Herrnstein, and later Murray, added to the argument was to say that IQ is not merely a genetically based, socially important variable—it is an actual measure of intelligence. The cultural differences in IQ scores, said Herrnstein, mean that blacks aren’t just innately less successful, they’re inherently stupider.
Call it Humpty-Dumpty genetics: if the character from Through the Looking Glass had been a scientist, facts would have meant what he wanted them to mean, neither more nor less.
As the population geneticist Richard Lewontin has been pointing out since Jensen’s article appeared, heritability is a measure of the genetic contribution to a trait within a population, under a given set of environmental conditions. It is the result of many-to-many relationships among genes, environmental variables, and interaction terms. It is meaningless to compare heritability across populations—or across races. Lewontin concluded that the only explanation for Jensen’s argument was an a priori conviction that compensatory education was pointless and that he had martialed a genetic argument to support it.
Personalized medicine is still racial. Although the genome gurus tout the universality and continuity of the geographical distribution of gene frequencies, they still use race as a genetic marker, a convenient bin that holds a large number of associated alleles. Race continues to play a fundamental role in haplotyping, a technique for distilling the bewildering mass of genomic data into categories the human brain can grasp. The genealogical panel offered by 23andMe and other DTC genomics companies testifies to the continuing genetic commitment to race in the genomic age.
IQ genetics is a hairsbreadth from a new and breathtaking racialization. Arbitrarily placed under “health,” nonverbal IQ could just as easily be moved into genealogy. Bingo, Arthur Jensen’s wet dream: Scientific proof of racial differences in intelligence.
Even without a racial correlation, IQ genetics is problematic. The “measures of intelligence” test is for a marker near a gene that explains about 3% of the variation in nonverbal IQ. Not much, and typical for single-gene assays for complex traits. The “measures of intelligence” test measures nothing more than a sliver of the variation in a gene correlated with a culturally biased test. Although 23andMe issues the right caveats, the average person will likely brush them aside. People want simple answers: Do I or do I not have the IQ gene?
A historical perspective on contemporary biomedicine helps us see how scientific facts have a context. It helps guide us to what we should be worrying about, in the present and in our immediate future. The bigger biomedicine gets, the more we need to mind its history.
References and Further Reading
Fleck, Ludwik. Genesis and Development of a Scientific Fact. Chicago: University of Chicago Press, 1979.
Gannett, Lisa. “Racism and Human Genome Diversity Research: The Ethical Limits Of “Population Thinking"." Philos Sci 63, no. 3(Suppl.) (2001): S479-92.
Gosso MF et al. (2006) . “The SNAP-25 gene is associated with cognitive ability: evidence from a family-based study in two independent Dutch cohorts.” Mol Psychiatry 11(9):878-86.
Gould, Stephen Jay. The Mismeasure of Man. New York: WW Norton, 1981.
Herrnstein, Richard J., and Charles A. Murray. The Bell Curve : Intelligence and Class Structure in American Life. New York: Free Press, 1994.
Herrnstein, Richard. “I.Q.” The Atlantic 228, no. 3 (1971): 43-64.
Jacoby, Russell, and Naomi Glauberman. The Bell Curve Debate. New York: Random House, 1995.
Jensen, Arthur. “How Much Can We Boost Scholastic Achievement?” Harvard Educational Review 39 (1969): 1-123.
Lewontin, Richard. “Race and Intelligence.” Bulletin of the Atomic Scientists 26, no. 3 (1970): 2-8.
Resta, Robert, “A DNA Day surprise,” The DNA Exchange, Aug. 15, 2010 (http://thednaexchange.com/).