Fazendo exceção com a eugenia humana - Mengele redivivus???

terça-feira, outubro 11, 2016

Taking Exception to Human Eugenics

Frederick P. Roth, John Wakeley

GENETICS October 1, 2016 vol. 204 no. 2 821-823; 


We are concerned that the Perspectives article “Mutation and Human Exceptionalism: Our Future Genetic Load” by Michael Lynch (2016) opens the dark chapter of eugenics without clearly reading it as a cautionary tale.
Given the history of eugenics, especially high standards for scholarship, sensitivity, and attention to historical context are needed when discussing the complex issues surrounding human genetic improvement. Statements similar to those Lynch makes in his article—which in the 1920s and 1930s were being made by leading population geneticists such as R. A. Fisher, J. B. S. Haldane, and H. J. Muller—led directly to eugenic policies and were later readily attached to the genocidal programs of Nazism (Kevles 1995). Failing to engage these issues, or offering vague recommendations, invites misappropriation by those who wish to see the return of an aggressive eugenics.
Lynch focuses on the rate and long-term consequences of deleterious mutations in humans. Despite concluding that humans are unexceptional in both germline and somatic mutation rates, he worries that deleterious mutations might accumulate in the future because of “exceptional” human behaviors that “thwart selection.” Specifically, by treating disease and reducing variation in the number of children per person, we reduce the impact of genetics on survival and procreation, and in turn threaten the “future of the human gene pool.”
Lynch contrasts deleterious mutations of large effect, which can be detected in parents or early-stage embryos (then “culled”), with mutations that are “impervious to detection” but have selective effects that can be ameliorated by medical intervention. We will refer to these as type 1 and type 2 mutations, respectively.
For type 1 mutations, Lynch quantifies the effectiveness of culling “in which a fraction fof the population is accurately screened for the mutation, with carrier chromosomes being culled upon detection.” He does not restrict this statement to prenatal screening, referring also to “direct screening in parents.” To be clear, Lynch did not advocate culling. However, he does ask us to entertain the idea, without specifically discussing the ethical minefield and horrifying history surrounding medical procedures without a net benefit to the recipient. For type 2 mutations, Lynch suggests that the extent to which we thwart selection is the extent to which “bad genes” will become prevalent and eventually exact their cost.
Some points in the article are argued poorly. On page 871, Lynch promises to back up the worrisome claim that our mutation rate is destined to increase, saying “...the possibility that the baseline human mutation rate will elevate over time (for reasons discussed below) motivates a strong argument...” yet he never delivers. Presumably “below” refers to the paragraph spanning the two columns of page 872, in which is it claimed that “hundreds of genetic loci influence the mutation rate either directly or indirectly,” without any citation. The paragraph ends with the statement: “It is therefore plausible that the human mutation rate is destined to slowly increase toward exceptional levels.” Despite Lynch’s additional promise early in the article (page 869) that “many of the issues addressed below were raised by Crow prior to the genomics revolution and can now be evaluated in a more quantitative way” (see Crow 19972000), there is no calculation here, only an undocumented claim of plausibility.