Several lines of evidence indicate that spicing may represent a class of cultural adaptations to the problem of food-borne pathogens. Many spices are antimicrobials that can kill pathogens in foods. Globally, common spices are onions, pepper, garlic, cilantro, chili peppers (capsicum) and bay leaves. Here’s the idea: the use of many spices represents a cultural adaptation to the problem of pathogens in food, especially in meat. This challenge would have been most important before refrigerators came on the scene. To examine this, two biologists, Jennifer Billing and Paul Sherman, collected 4578 recipes from traditional cookbooks from populations around the world. They found three distinct patterns.
1. Spices are, in fact, antimicrobial. The most common spices in the world are also the most effective against bacteria. Some spices are also fungicides. Combinations of spices have synergistic effects, which may explain why ingredients like “chili power” (a mix of red pepper, onion, paprika, garlic, cumin and oregano) are so important. And, ingredients like lemon and lime, which are not on their own potent anti-microbials, appear to catalyze the bacteria killing effects of other spices.
2. People in hotter climates use more spices, and more of the most effective bacteria killers. In India and Indonesia, for example, most recipes used many anti-microbial spices, including onions, garlic, capsicum and coriander. Meanwhile, in Norway, recipes use some black pepper and occasionally a bit of parsley or lemon, but that’s about it.
3. Recipes appear to use spices in ways that increase their effectiveness. Some spices, like onions and garlic, whose killing power is resistant to heating, are deployed in the cooking process. Other spices like cilantro, whose antimicrobial properties might be damaged by heating, are added fresh in recipes.
Thus, many recipes and preferences appear to be cultural adaptations adapted to local environments that operate in subtle and nuanced ways not understood by those of us who love spicy foods. Billing and Sherman speculate that these evolved culturally, as healthier, more fertile and more successful families were preferentially imitated by less successful ones. This is quite plausible given what we know about our species’ evolved psychology for cultural learning, including specifically cultural learning about foods and plants.