Throwing new light on the origins of present-day Europeans, a team of international researchers has traced their roots to three ancestral groups and not two as was believed. The results of the study have been published today (September 18) in Nature .
The consortium led by researchers from the University of Tubingen and Harvard Medical School in collaboration with scientists from the Centre for Cellular and Molecular Biology (CCMB), Hyderabad, studied three different ancient human bone samples and compared them with 200 diverse contemporary populations across the world through genome-wide data of about 2,400 humans. The contemporary populations included the enigmatic tribal population of Andaman and Nicobar Islands, according to Dr. Kumaraswamy Thangaraj, one of the authors of the study and Senior Principal Scientist at CCMB.
The study analysed ancient human genomes from a more than 7,000-year-old early farmer from Stuttgart in Southern Germany, belonging to linearbandkeramik (LBK), a sedentary farming culture, a more than 8,000-year-old hunter-gatherer from the Loschbour rock shelter in Luxembourg, and seven over 8,000-year-old hunter-gatherers from Motala in Sweden.
Tremendous impact According to a CCMB release, the beginning of agriculture and animal domestication, which began in the Near East about 11,000 years ago, had a tremendous impact on human lifestyle. Hunter-gatherers were replaced in many places by farmers and there were large increases in population size that laid the foundation for larger towns and eventually complex societies.
Archaeological evidence suggests that a transition to a farming lifestyle in Central Europe occurred around 7,500 years ago with the appearance of LBK.
While the first ancestral group was indigenous hunter-gatherers; the second comprised Middle Eastern farmers that migrated to Europe around 7,500 years ago. The novel third group is a more mysterious population that spanned North Eurasia and genetically connects Europeans and Native Americans.
All three groups The researchers calculated the proportion of the ancestral components in present-day Europeans and found that all Europeans have ancestry from all three groups. While Northern Europeans have more hunter-gatherer ancestry (up to 50 per cent in Lithuanians), Southern Europeans have more farmer ancestry.
The Northern Eurasian ancestry was the smallest component and never more than 20 per cent.
Dr. Thangaraj said that a genetic mutation was introduced to digest milk-sugar in humans after they domesticated cattle and started drinking milk. Hunter-gatherers and early farmers had high copy numbers of amylase in their genomes suggesting they had already adapted to a starch-rich diet. This amylase factor was more common in Europeans, Middle Eastern people and North West Indians.
Indian emergence CCMB scientists earlier found that Indians emerged from two ancestral populations — ancestral South Indians (ASI) and ancestral North Indians (ANI). While ASI did not have any genetic affinity outside India, ANI showed up to 70 per cent genetic affinity with Europeans. “However, it would be interesting to see which one of the three ancestral European populations is related to ANI”, says Dr. Lalji Singh, formerly Director of CCMB and also a co-author of the study.
Dr. Thangaraj says he suspected that the Middle Eastern component of milk-digesting gene might have contributed to ANI.