Jensen From Behavior to Genes and Back Again
What should babies be screened for, and who should share in the data? Credit: BSIP/UIG via Getty
Blueprint: How DNA Makes United states of america Who We Are Robert Plomin Allen Lane (2018)
Information technology's never a skillful time for another bout of genetic determinism, but it's hard to imagine a worse 1 than this. Social inequality gapes, exacerbated by climate change, driving hostility towards immigrants and flares of militant racism. At such a juncture, nonetheless another expression of the discredited, simplistic idea that genes alone command human nature seems particularly insidious.
And yet, here nosotros are once more with Blueprint, by educational psychologist Robert Plomin. Although Plomin oft uses more civil, progressive language than did his predecessors, the book'due south message is vintage genetic determinism: "Deoxyribonucleic acid isn't all that matters but it matters more than everything else put together". "Nice parents have nice children because they are all prissy genetically." And it's not just any nucleic acid that matters; it is human chromosomal DNA. Sorry, microbiologists, epigeneticists, RNA experts, developmental biologists: you're non part of Plomin'due south picture.
Rough hereditarianism often re-emerges after major advances in biological knowledge: Darwinism begat eugenics; Mendelism begat worse eugenics. The flowering of medical genetics in the 1950s led to the notorious, now-debunked idea that men with an extra Y chromosome (XYY genotype) were decumbent to violence. Hereditarian books such equally Charles Murray and Richard Herrnstein's The Bong Curve (1994) and Nicholas Wade'due south 2014 A Troublesome Inheritance (see N. Comfort Nature 513, 306–307; 2014) exploited their respective scientific and cultural moments, leveraging the cultural authorization of science to accelerate a discredited, undemocratic agenda. Although Pattern is cut from different ideological cloth, the consequences could be but as grave.
The scientific advance this time is the genome-broad association report (GWAS). Invented in 1996, GWAS has gained massively in predictive power with the appearance of 'polygenic scores', a statistical tool that in contempo years has lured social scientists to the genome, with the promise of genetic explanations for complex traits, such equally voting behaviour or investment strategies. As Plomin notes, it was something they had been trying to do for a long time.
Plomin's predecessors tried to get monogenic take chances scores. For instance, Henry Goddard, an educational psychologist who from 1906 to 1918 directed the New Bailiwick of jersey Training School for Feeble-Minded Girls and Boys in Vineland, claimed he had found the gene for low intelligence. With Charles Davenport, a prominent US eugenicist, whispering in his ear, Goddard suggested that learning disabilities resulted from a single Mendelian recessive gene. Scanning the swathes of pedigrees he had collected (progressive-era 'large information'; encounter D. Dobbs Nature 558, 28–29; 2018), he identified what seemed to be a unit character: an apparent recessive "gene for" learning disability. When he factored in behaviours idea to result from that condition — such as misdeed and promiscuity — the alleged association went heaven-high. Goddard's pedigrees bloomed with antisocial traits, which he believed were passed down the generations as a Mendelian recessive cistron. He never seems to have questioned whether a single gene for such a complex trait made sense biologically. Information technology doesn't.
No one is so foolish as to believe in a single factor for learning disability any more. As has been well established, the genetic contribution to complex traits is spread over many genes, each contributing a minuscule sliver of the variability for the trait. Polygenic chance scores sum and weight these many tiny effects, creating what some researchers have chosen a "monogenic equivalent"— a "gene for" past proxy.
A polygenic score is a correlation coefficient. A GWAS identifies unmarried nucleotide polymorphisms (SNPs) in the Deoxyribonucleic acid that correlate with the trait of interest. The SNPs are markers only. Although they might, in some cases, advise genomic neighbourhoods in which to search for genes that directly bear on the trait, the polygenic score itself is in no sense causal. Plomin understands this and says so repeatedly in the book — even so contradicts himself several times past arguing that the scores are, in fact, causal.
Plomin deploys a standard feint in hereditarian psychology, insisting on the trivial so‑called first constabulary of behavioural genetics: that no psychological trait is entirely unaffected by genetics. But he insists that "genetics is the main systematic force in life", often mediating both gene–environment effects and even environmental effects, such every bit breastfeeding and TV-watching on school achievement. If all you lot accept is a polygenic score, everything looks like a gene. Blueprint is uncritical DNA boosterism, and Plomin "unabashedly a cheerleader" by his own admission.
Polygenic scores practise suggest some things to cheer most. We should applaud the wide-based shift beyond biomedicine from monogenic to polygenic causation. This approach analyses behaviour in a much more complex, surgical way than the rough stabs of Goddard's ilk. The method is finding wide application, from precision medicine to field biology. For example, polygenic scores have been shown to improve risk predictions for prostate, ovarian and breast cancers. They can point to traits that might have been influenced by local adaptation, and estimate the pace of evolutionary change.
Plomin adopts the language of personalized medicine to phone call for DNA-driven advances in education policy — "personalized learning". He argues that nosotros should think of personality traits as we practice autism or attention-deficit hyperactivity disorder: as existing on spectra. He urges psychologists to move away from the language of disorders and to talk instead of graded "dimensions"— personality traits, such as introversion or agreeableness. "All children have special needs," he in one case told the paper The Guardian. In a book so filled with retrograde ideas well-nigh genes, I was pleasantly surprised to find this strong, welcome biological support for the idea of neurodiversity.
In fundamental means, however, Plomin'southward argument is just one-time hereditarian vino pipetted into thousands of tiny polygenic bottles. In 1969, educational psychologist Arthur Jensen dropped a pseudo-statistical bombshell in the Harvard Educational Review. He argued that genetics was responsible for the notional IQ gap between African Americans and white people (non bias broiled into the test or environmental effects) and that remedial education was pointless. Jensen's arguments and much of his 'information' were old, part of a dark tradition of hereditarian social science that would subsequently emerge in books such as The Bell Bend. Design uses language, imagery, rhetoric, conclusions and numbers that will be familiar to readers who have, like me, slogged through all these works. A sobering theme of most, Blueprint included, is their aspiration of shaping social policy.
Like much of that literature, Blueprint plays fast and loose with the concept of heritability. Sometimes Plomin treats it (correctly) as a variable property of a population in a given environment. As population geneticist Richard Lewontin pointed out in a scathing critique of Jensen'southward arroyo in 1970, in times of plenty, acme is highly heritable; in a famine, much less and then (R. C. Lewontin Bull. Atom. Sci. 26, ii–8; 1970). Just elsewhere, Plomin, like Jensen, treats heritability wrongly as a property inherent in a trait.
Pattern does depart from much prior hereditarian social science in non explicitly mentioning race — the hot-button issue of many earlier works. It instead looks at class. Plomin uses a data set up of by and large white British twins, most of whom attended English language grammer schools. Still, given Plomin's extensive feel and his footnotes, the absence of whatsoever explicit mention of race (to disavow it, say, or to allude to intersectionality) is conspicuous.
The most troubling affair about Blueprint is its Panglossian DNA determinism. Plomin foresees individual, directly-to-consumer companies selling sets of polygenic scores to bookish programmes or workplaces. Yet, as this "incorrigible optimist" assures usa, "success and failure — and credit and blame — in overcoming problems should exist calibrated relative to genetic strengths and weaknesses", not environmental ones. All is for the best in this best of dauntless new worlds.
Plomin likes to say that various components of nurture "matter, just they don't brand a deviation". Just the benefits of skilful education, of school lunches and breakfasts, of having textbooks and air-conditioning and heating and plumbing have been established irrefutably. And they actually are causal: nosotros know why stable blood sugar improves mental concentration. Withal Plomin dismisses such effects as "unsystematic and unstable, and then there'south non much we can practise virtually them".
Ultimately, if unintentionally, Pattern is a road map for regressive social policy. Nada hither seems overtly hostile, to schoolchildren or anyone else. Only Plomin'southward argument provides alive ammunition for those who would abandon proven methods of improving bookish achievement among socio-economically deprived children. His utopia is a forensic earth, dictated by polygenic algorithms and the whims of those who know how to utilize them. People would exist defined at birth by their Dna. Expectations would be set, and opportunities, resources and experiences would be doled out — and withheld — a priori, earlier anyone has had a chance to show their mettle.
To paraphrase Lewontin in his 1970 critique of Jensen's argument, Plomin has made information technology pretty clear what kind of world he wants.
I oppose him.
Source: https://www.nature.com/articles/d41586-018-06784-5
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