Agricultural expansion was such a momentous event that cultural or genetic evidence of its impact should be apparent. Abundant evidence indicates that agriculture was introduced into Europe at least 9,000 years ago. The primary issue remains whether agriculture spread by contact or by farmers moving into Europe. If agriculture was brought by farmers moving into foragers' territory, then genetic evidence should be apparent in the genes of modern Europeans. If foragers weredisplaced, then European genetic profiles should reflect the source population from the Near East. If there was interbreeding with the foragers who had a distinct genetic profile, then the genes of the Europeans descendants should reflect this admixture, with a clinal distribution of traits radiating from the Near East. These scenarios have been the focus of decades of debates between anthropologists and geneticists. In addition, genomic studies have been applied to pathogens in order to explore the link between agriculture and infectious disease.