{"id":4098,"date":"2019-09-18T13:27:19","date_gmt":"2019-09-18T04:27:19","guid":{"rendered":"http:\/\/163.180.4.222\/lab\/?p=4098"},"modified":"2019-09-18T13:27:19","modified_gmt":"2019-09-18T04:27:19","slug":"new-middle-chapter-in-the-story-of-human-evolution","status":"publish","type":"post","link":"https:\/\/biochemistry.khu.ac.kr\/lab\/?p=4098","title":{"rendered":"New middle chapter in the story of human evolution"},"content":{"rendered":"

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By comparing genetic information from extant humans worldwide, researchers have painted a broadstrokes picture of human prehistory. However, these data reveal only the oldest and most recent chapters of the story of human evolution. On page 999 of this issue, Narasimhan\u00a0et al.<\/em>\u00a0(1<\/em><\/a>) capitalize on recent advances in high-throughput genome sequencing techniques and access to well-preserved ancient human remains to write a key middle chapter of this story.<\/p>\n

Over the past 100,000 years or so, humans dispersed across Africa and then throughout the rest of the world, consequently adapting to a wide variety of lands, climates, and ecosystems (2<\/em><\/a>). This basic narrative illuminates questions\u2014about local adaptation, ecosystem disruption, linguistic evolution, and human prehistory\u2014that genomic data from extant humans fails to answer. To address this deficiency, Narasimhan\u00a0et al.<\/em>\u00a0built on previous large-scale studies of human migration history conducted with ancient DNA obtained from human remains across Eurasia (3<\/em><\/a>\u20136<\/em><\/a>) (see the figure). The authors sequenced more than 500 genomes of humans belonging to ancient cultures from archaeological sites across a large part of Asia. They then used an array of allele frequency\u2013based statistics and algorithms to model human populations across time as mixtures of other, earlier populations and investigated outstanding questions about human dispersals in South and Central Asia. Although this effort does not rewrite the history of humans in South Asia, it does fill in several missing pieces.<\/p>\n

Despite the archaeological and historical importance of the Copper Age Indus Valley Civilization in the northwest regions of South Asia, the genetic origins of the people of this culture remain uncharacterized. Narasimhan\u00a0et al.<\/em>\u00a0identified 11 individuals who lived in regions adjacent to, but outside of, South Asia between 3300 and 2000 BCE and whose genetic signatures indicate that they were migrants from the south. Each of these migrant genomes was a mixture of one population comprising mostly early Iranian farmers and another resembling hunter-gatherers from the Andaman Islands south of India. These two groups mixed between 5400 and 3700 BCE, forming a genetic signature detectable in South Asian genomes today. Because these South Asian migrants were contemporaneous with the Indus Valley Civilization, Narasimhan\u00a0et al.<\/em>\u00a0inferred that the migrants’ genetic profile was probably typical of members of the Indus Valley Civilization. Thus, their study provides evidence of the genomic origins of the Indus Valley Civilization despite not including any ancient genomes from the Indus Valley Civilization itself.<\/p>\n

These new data also suggest that, after the fall of the Indus Valley Civilization, several migrations into South Asia led to the formation of two distinct populations therein, one more ancestral to modern North Indians and the other more ancestral to modern South Indians. The ancestry of most present-day Indians is probably composed of these two populations along with a handful of others (6<\/em><\/a>\u20138<\/em><\/a>). The ancestral South Indian population formed as individuals typical of the Indus Valley Civilization continued to mix with a population related to today’s Andaman Islanders; this genomic mixing likely persisted until as late as 1700 to 400 BCE.<\/p>\n

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