There is little evidence that spicy food in hot countries is an adaptation to reducing infection risk

Spicier food in hot countries has been explained in terms of natural selection on human cultures, with spices with antimicrobial effects considered to be an adaptation to increased risk of foodborne infection. However, correlations between culture and environment are difficult to interpret, because many cultural traits are inherited together from shared ancestors, neighbouring cultures are exposed to similar conditions, and many cultural and environmental variables show strong covariation. Here, using a global dataset of 33,750 recipes from 70 cuisines containing 93 different spices, we demonstrate that variation in spice use is not explained by temperature and that spice use cannot be accounted for by diversity of cultures, plants, crops or naturally occurring spices. Patterns of spice use are not consistent with an infection-mitigation mechanism, but are part of a broader association between spice, health, and poverty. This study highlights the challenges inherent in interpreting patterns of human cultural variation in terms of evolutionary pressures. Spices with antimicrobial effects have been considered to be a Darwinian adaptation to reduce risk of foodborne infection. Bromham et al. analyse more than 30,000 recipes and find that spice use is more strongly associated with socioeconomic factors than infectious disease.