Clarence Gravlee, Amy Non and Connie Mulligan have just published an outstanding article in PLoS ONE, Genetic Ancestry, Social Classification, and Racial Inequalities in Blood Pressure in Southeastern Puerto Rico. The abstract opens:

The role of race in human genetics and biomedical research is among the most contested issues in science. Much debate centers on the relative importance of genetic versus sociocultural factors in explaining racial inequalities in health. However, few studies integrate genetic and sociocultural data to test competing explanations directly.

Note how that fits so well into the points just made in Nature/Nurture: Slash to the Rescue. But Gravlee, Non and Mulligan don’t just say we need to overcome the nature vs. nurture dichotomy, they do research that bridges it and even better, test ideas on both sides: “We draw on ethnographic, epidemiologic, and genetic data collected in southeastern Puerto Rico to isolate two distinct variables for which race is often used as a proxy: genetic ancestry versus social classification.”

This type of collaborative research can be crucial to getting the data to answer complicated questions. Connie Mulligan and Lance Gravlee deserve credit for taking the time to discuss how to bring together their respective approaches before going out to do research. In this case, the data come down more on the nurture (or social) side. As they write:

Our preliminary results provide the most direct evidence to date that previously reported associations between genetic ancestry and health may be attributable to sociocultural factors related to race and racism, rather than to functional genetic differences between racially defined groups.

Before someone gets all hot and bothered, Lance has also shown how to bring nurture back to nature. In Gravlee’s recent paper, How Race Becomes Biology: Embodiment of Social Inequality (pdf), he gives us following: “Drawing on recent developments in neighboring disciplines, I present a model for explaining how racial inequality becomes embodied – literally – in the biological well-being of racialized groups and individuals. This model requires a shift in the way we articulate the critique of race as bad biology.”

In the PLoS paper, Lance, Amy and Connie are aiming squarely at the use of race in medicine, where it has become common in some circles to use racial classification as a proxy for genetics. Basically this research destroys the proxy notion, since social classification turns out to be a better predictor of blood pressure than genetic ancestry.

Yet the research also highlights that genetics does play a role, just not in the broad way we normally think (nature as cause). Specifically the data revealed an association between systolic blood pressure and a specific polymorphism, α2C adrenergic receptor deletion, only when social classification and socioeconomic status were included in the analysis.

This research also reveals social complexity. As the figure from the PLoS paper above indicates, there are interactions between racial classification, socioeconomic status, and systolic blood pressure in Puerto Rico. The basic conclusion is the opposite of what many of us might expect – those perceived as darker (negro) have higher blood pressure when in a higher social class. Conversely, those with lighter skin have higher blood pressure with lower SES. These results can be related to complex social dynamics. Darker colored individuals likely face more racial discrimination when in a higher SES because Puerto Rico is still a racially divided country, with wealth and status running lighter to darker. Here is the PLoS paper:

The pattern we observe is consistent with the hypothesis that social classification based on color entails differential exposure to social stressors related to blood pressure. In particular, there is ethnographic evidence that Puerto Ricans perceived as negro, as compared to trigueño or blanco, may encounter more frequent frustrating interactions in high-SES settings due to institutional and interpersonal discrimination.

Put in a broader sense, this paper points to the need to actively consider social inequality and discrimination as causes of health problem, something the “race as genetics” idea completely fails to do. Along with colleagues, Gravlee has made this point forcefully in a previous paper, Race and Ethnicity in Public Health Research: Models to Explain Health Disparities.

At the end of the PLoS paper Lance, Amy and Connie highlight an important direction for future research: “Although our measure of social classification improves on existing approaches, further research is needed to assess how well it approximates the ascription of color in everyday social interaction. Future research could build on our measurement approach by testing whether non-biological markers of social status (e.g., hair style, dress, speech) influence social classification.”

I’d also encourage Lance and his colleagues to look more closely at perceived discrimination, that this is also a crucial mediator of how race ends up driving biology. It’s not just consensus about racial classification, but how an individual person reacts to that. This point is made broadly by Robert Sampson when he discusses perceptions of disorder as an important force behind disparity. Building an ethnographically informed measure of subjective discrimination could add an important link in the pathway from social inequality to changes in blood pressure.

But this paper also challenged me. What is particularly good is that Lance builds on previous research that established how social classification according to “color” trumps actual skin pigmentation in establishing race and in impacting health. Now he and Connie have taken that a step further to get the data and test both biological and cultural ideas.

So this morning I am thinking more seriously how I could better examine the nature/nurture debate around addiction (quite similar in form to the race and health debate – biology does it; no, it’s inequality). How can studying sin become a closer look at how people get engaged in destructive behaviors, and which factors (working together, I’d say) are most important? Because right now the biologists are going to say, well it’s dopamine (or glutamate or whatever neurotransmitter is the flavor of the day) and the anthropologists are going to say, well it’s meaning. I’m still stuck at saying “holistic interactionism” (as Pinker would put it) rather than showing more concretely how the two come together and then relating both to genetics and to symbolism.

Lance Gravlee, Amy Non and Connie Mulligan have already taken that next concrete step. Kudos!

For more on Lance Gravlee’s work, please visit his website. For more on Connie Mulligan’s work, here’s her UF website.

For those looking for coverage of some of the paper’s highlights, you can check out the University of Florida’s press release, Socio-cultural, genetic data work together to reveal health disparities.

Gene Expression also provides a useful summary with Hypertension, Race, Class and Puerto Rico, including a comment by Lance clarifying a couple points.

And here’s the link for the PLoS full text of Genetic Ancestry, Social Classification, and Racial Inequalities in Blood Pressure in Southeastern Puerto Rico.