Person:

Shattuck-Heidorn, Heather

We present a critique of a paper written by two economists, Quamrul Ashraf and Oded Galor, which is forthcoming in the American Economic Review and which was uncritically highlighted in Science magazine. Their paper claims there is a causal effect of genetic diversity on economic success, positing that too much or too little genetic diversity constrains development. In particular, they argue that “the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions.” We demonstrate that their argument is seriously flawed on both factual and methodological grounds. As economists and other social scientists begin exploring newly available genetic data, it is crucial to remember that nonexperts broadcasting bold claims on the basis of weak data and methods can have profoundly detrimental social and political effects.

Abstract Background and objectives: The human immune system is an ever-changing composition of innumerable cells and proteins, continually ready to respond to pathogens or insults. The cost of maintaining this state of immunological readiness is rarely considered. In this paper we aim to discern a cost to non-acute immune function by investigating how low levels of C-reactive protein (CRP) relate to other energetic demands and resources in adolescent Gambian girls. Methodology: Data from a longitudinal study of 66 adolescent girls was used to test hypotheses around investment in immune function. Non-acute (under 2 mg/L) CRP was used as an index of immune function. Predictor variables include linear height velocity, adiposity, leptin, and measures of energy balance. Results: Non-acute log CRP was positively associated with adiposity (β = 0.16, P < 0.001, R2 = 0.17) and levels of the adipokine leptin (β = 1.17, P = 0.006, R2 = 0.09). CRP was also negatively associated with increased investment in growth, as measured by height velocity (β = −0.58, P < 0.001, R2 = 0.13) and lean mass deposition β = −0.42, P = 0.005, R2 = 0.08). Relationships between adiposity and growth explained some, but not all, of this association. We do not find that CRP was related to energy balance. Conclusions and implications: These data support a hypothesis that investment in non-acute immune function is facultative, and sensitive to energetic resources and demands. We also find support for an adaptive association between the immune system and adipose tissue.

The sex disparity in COVID-19 mortality varies widely and is of uncertain origin. In their recent Nature paper “Sex differences in immune responses that underlie COVID-19 disease outcomes," Takahashi et al. assess immune phenotype in a sample of COVID-19 patients and conclude that the “immune landscape in COVID-19 patients is considerably different between the sexes,” warranting different vaccine and therapeutic regimes for men and women -- a claim widely disseminated following the publication. Here, we argue that these inferences are not supported by their findings: this study does not demonstrate that biological sex explains COVID-19 outcomes among patients. This study is diagnostic of an ongoing pattern in sex difference research of overstatement of findings and superficial treatment of factors beyond innate sex in analyzing the causes of gender/sex disparities in health outcomes.