The coevolutionary relationship of humans and domesticated plants

Human-plant interactions have figured prominently in our species' evolution and they continue to influence the contemporary geographical patterns of human biodiversity. The domestication of particular plant taxa has genetically modified those taxa and intensified human contact with specific plants and their endogenous bioactive allelochemicals (secondary plant compounds). This contact, sustained over multiple generations of humans and plants has provided, on occasion, unique opportunities for amplified interactions of microevolutionary importance. In this paper, a theoretical overview of these interactions is presented and four case studies are detailed as examples of local potentially coevolutionary specificity. The first set of case studies include two human-plant diads: 1) salivary proline-rich proteins and carcinoma in East Asian ethnic groups and ingestion of tea (Camellia sinensis) flavonoids (polyphenols) and 2) HLADQ2+ phenotypes and celiac disease in Northern Atlantic European ethnic groups and ingestion of wheat (Triticum aestivum) A-gliadin peptides. Since established human-plant interactions frequently involve a third species, the second set of case studies includes two human-plant-parasite triads: 1) red blood cell G6PD variants similar to Gdmed and favism in Mediterranean ethnic groups and ingestion of fava bean (Vicia faba) glycosides and exposure to Plasmodium falciparum malaria and 2) HbβS phenotypes and sickle cell anemia in West African ethnic groups and ingestion of cassava (Manihot esculenta) cyanogenic glucosides and exposure to Plasmodium falciparum malaria.