Biodemography--Learning About Ourselves By Studying Other Animals

The National Research Council just published a volume on "Sociality, Hierarchy, Health: Comparative Biodemography: Papers from a Workshop." Now, I admit that this is unlikely to lead to a hit series on HBO, but it really is fascinating. The major takeaway is that humans are not the only species in which we find a social gradient in health. Higher status animals routinely have better health and typically live longer than those at the bottom of the hierarchy. And, yes, most animal species have these social gradients--this is not something unique to humans. The first chapter in the volume is by Maxine Weinstein, Hillard Kaplan, and Meredith A. Lane, who nicely summarize the volume, but I especially like some of the comments in the final chapter by Michael G. Marmot and Robert Sapolsky. For example, one might well speculate that low social rank is caused by poor health, rather than things being the other way around. However, longitudinal studies of baboons suggests that...

While poor health can certainly lead to low social rank, the longitudinal data in these studies demonstrate that the pathophysiological correlates of subordination follow, rather than precede, the establishment of a rank. We argue that, as with the human health gradient, this rank/health link is mostly psychosocial in nature.

This is partly because the social gradient in health exists in high and low mortality societies, suggesting that it has little to do with the amount of food, for example, or the gene pool of the species. Studying non-humans helps us to understand humans.

One clear advantage of studying nonhuman primates is their very nonhumanness. Many of the candidates put forward to explain health inequalities in humans simply are not seen in other species. Baboons don’t smoke, eat fast foods, or have differential access to health care depending on ability to pay. A stressed primate, however, will have similar physiological responses to those of a stressed human. There is insight to be gained not only in understanding the biological pathways by which social position affects health, but also in understanding the circumstances under which these
physiological responses are evoked. They lend credence to our claim that psychosocial factors play a major role in generating the social gradient in health.

The bottom line for humans and non-humans is that context matters. You cannot understand health just by studying individuals. You have to put them into context. Indeed, an important part of that context is inequality. Greater inequality may be bad for your health, not just your pocketbook--unless of course you are in the top 1 percent.