Noted: The connection between TRPM8 and migraine isn’t clear, other than the association. “Selection is optimizing fitness,” says anthropologist John Hawks of the University of Wisconsin-Madison who was not associated with the study. “It doesn’t optimize health, it doesn’t optimize happiness, so sometimes things are pushed by selection and they have negative side effects. This seems to be a case where a gene is pushed higher in frequency by selection for adaptation to cold, and it maybe has a bad side effect on increased susceptibility to migraines.” It’s also possible that the downside to having the cold-adaptive TRPM8 allele is a modern phenomenon, and that the migraine risk didn’t appear until more recently as environments have changed, says Nielsen.