Why Some Like It Hot: Food, Genes, and Cultural Diversity by Gary Paul Nabhan.  http://www.amazon.com/Why-Some-Like-Hot-Diversity/dp/1597260916/ref=sr_1_1?ie=UTF8&s=books&qid=1268854442&sr=8-1

My library had a copy.  Basically, the guy is a ethnobotanist who compared the human genome with cultural food choices and found some interesting connections.  Fava beans may create a physical response to the malarial parasite similar to sickle cell anemia.  That is, if you are sensitive to fava beans, eating them will cause your red blood cells to collapse if exposed to the parasite, thereby reducing your susceptibility to malaria.  So in Mediterranean cultures, fava beans are prepared at a certain time of year in a certain manner that actually increases the resistance.  People who come from cultures that are cattle herders are generally lactose tolerant, all other mammals (including people from non-cattle herding cultures) are lactose intolerant once they are mature adults.  Lots of other examples - alcohol and alcoholism, native diets and diabetes, the Mediterranean diet are some I remember.  He combines science and anecdotal evidence for an interesting read.