Several years ago, a team of researchers from Cornell University proposed that the spices used in traditional meat-based cuisines originally served not as flavor, but to stave off bacteria and fungi. Now new research is providing further food for thought: findings reported in the June issue of Evolution and Human Behavior explain why vegetable-based dishes tend to lack such spiciness.

Plants, it turns out, don't require so much protection against microorganisms as meats because they have their own natural chemical and physical defenses, which continue to function after cooking. Cornell neurobiologist Paul W. Sherman and undergraduate Geoffrey Hash thus predicted that if spices first served as antimicrobials, especially in warmer climates, vegetable recipes in the same countries surveyed for the meat research should feature fewer spices. Subsequent investigation bore this out. Analyzing 2,129 traditional vegetable recipes from 36 different countries, the team found that spice usage was far lower than that found in meat-based dishes from the same cultures. Indeed, of the 41 spices considered, 38 appear more frequently in meat recipes; the three that don't fit this patternsesame, caraway and sweet pepperoffer little protection anyway.

"Humans have always been in a co-evolutionary race with parasites and pathogens in foods, and our cookbooks are the written record of that race," Sherman asserts. "We haven't had to 'run' as hard when we ate vegetables. We haven't had to use extra pharmaceuticals to make vegetables safe for consumption."