Editor's Note: This is the third part of a TNR debate about genetics and race. To read Merlin Chowkwanyun's original article, click here. To read Justin Shubow's response, click here, and to read Chowkwanyun's rebuttal, click here.

Dear Merlin,

I, too, hope that this fruitful debate doesn't conclude here, especially since, contrary to your mischaracterization, I don't think that science, while getting closer to the truth over time, ever reaches an endpoint.

To be clear, I didn't intend my remark about Latino life-expectancy to justify the use biological race in science or social science. I completely agree that "Latino" is an overbroad, unscientific category of limited use. I raised the statistic merely to shed doubt on the view that all disparities in group health statistics must be the result of environmental, as opposed to genetic, factors--a position that, given the space you devote to it in your reply, you seem to hold dear.

Though I mentioned only life-expectancy, you'll be interested to know that the "Hispanic Paradox" also includes the findings that, relative to non-Latino whites, Latinos have lower rates of cancer, heart disease, and strokes, as well as lower infant mortality rates--all of this despite their having a similar socioeconomic status to blacks, and being "even more likely to lack health insurance and have low health utilization rates." A number of factors are likely at work, including cultural ones such as diet and family structure, but genetics is also a significant possibility. Some epidemiologists have surmised that the paradox can be partly explained by the genetic benefits of having such a mixed ancestry, in contrast to the situation of highly endogamous groups, which are more prone to various diseases. To be sure, not every aspect of Latinos' ancestry has been a boon: Their susceptibility to diabetes could be caused by certain genotypes that were passed down from Native Americans, who seem likewise to be predisposed to the disease.

While you're right to criticize those who too hastily accept reductionist genetic explanations for social phenomena, the interesting question is why you are so eager to go to the opposite extreme. (I'm reminded of Timothy Noah's quip that conservatives think everything is genetic except homosexuality, whereas liberals think nothing is genetic except homosexuality.) My sense is that--like Jay Kaufman, the epidemiologist you cite who has been the leading critic of the slavery hypothesis--you find nothing but danger in the idea of "genetic determinism." As Kaufman writes in an article attacking that hypothesis, "The myth of genetic determinism cuts both ways... for although it absolves the individual from responsibility, it also absolves the society at large. 'Deterministic biological explanations ("it's in my genes")--much like theological explanations ("the devil made me do it")--locate problems (and, therefore, solutions) within individuals.'" But surely this is an odd claim to make regarding the slavery hypothesis, which explicitly holds that its purported "deterministic biological explanation" for black hypertension is the result of wrongs performed by humans over 200 years ago. It certainly doesn't absolve that slave-trading society from responsibility. And to the extent that our society is liable for its distant past wrongs, we too are liable.

In any event, Kaufman's worry, which you seem to share, confuses the origin of a harmful condition with who is responsible for ameliorating it. Suppose that some people are born sickly as a result of random genetic mutations--i.e., due to bad luck. Why can't a society, or any particular person, still be morally required to help them? There's no reason to think that blameworthiness is required for obligation.

As for my avoiding the substance of the slavery hypothesis, I preferred to address the fundamental considerations regarding the intersection of race, genetics, and science before evaluating any particular application of them. I also find that it's typically unhelpful to examine a general subject via distracting, let alone inflammatory, examples--as the saying goes, you don't teach anatomy with the bust of Marilyn Monroe.

For what it's worth, while I find the slavery hypothesis highly speculative and still unproven, it's a gross overstatement to say it has been "demolished on theoretical and evidentiary grounds." The January 2003 issue of Epidemiology contains a symposium in which Clarence Grim and others reply to the above-mentioned article by Kaufman. Among other things, the respondents cite research showing that when faced with increased sodium intake, black Americans retain more of the element in their body than do whites--a demonstration of the sort of physiological trait that would have survival advantages in low-sodium environments. They also counter Philip D. Curtin's historical claims, upon which you so heavily rely, by citing newer research on morbidity in the American slave trade, and they also raise doubts about the Curtin's understanding of the pathology of sodium depletion.

One thing they should have mentioned, but didn't, is another instance in which Curtin's grasp of the relevant science is weak. In his paper, he argues that "To make [their] case, Wilson and Grim would have to show that a physiologically traumatic experience lasting less than a year could have genetic consequences more than 2 centuries later. These authors point to the persistence of the sickle-cell trait in African Americans, but that trait was able to develop through about 5000 years of exposure to falciparum malaria." In thinking that this is a strong counterargument, Curtin shows himself to be totally unaware of the widely-accepted theory of "genetic bottlenecks," which can rapidly and dramatically alter a population's genotypes. (A prominent example of a hypothesis employing that concept is Stanley H. Ambrose's Toba Catastrophe Theory, which attempts to explain--ironically enough, given our debate--the surprising lack of variability in our species. He proposes that a super-volcanic eruption some 70,000 years ago created a six-year global winter that decimated the human population and fundamentally altered the gene pool.)

Like C. P. Snow and yourself, I agree that there needs to be better communication between the sciences and humanities, but, as the example of Curtin suggests, the same must be said for the divide between the sciences and the social sciences. Moreover, I disagree about the direction in which there is the greatest need for consultation. While you say we need to avoid "questionable faith-based initiatives," it is non-scientist academics who all-too-often profess the "New Creationism" that refuses to apply biological understandings to human beings. It is they, not genetic or medical researchers, who tend to be guilty of unempirical fideism.

Best,
Justin

By Merlin Chowkwanyun