In the most comprehensive study to date on the genetic origins of Native Americans, an international research team confirmed that Native Americans who descended from ancestors who crossed from Asia to the Americas approximately 20,000 years ago are offspring of six founding, or ancestral, mothers. The study also confirms the presence of genetic subgroups of more rare, less known and geographically limited genetic groups who arrived later. This study is the first time all known Native American mitochondrial DNA (mtDNA) sequences and lineages have been compiled, corrected and organized into a single tree with branches dated.
Researchers from the Sorenson Molecular Genealogy Foundation (SMGF), a non-profit foundation building the world's largest collection of integrated genetic and family history information, the department of genetics and microbiology at the University of Pavia, and others today published online at the Public Library of Science (www.plos.org) the results of their study of more than 200 full mtDNA sequences from Native Americans. mtDNA traces maternal ancestry for both men and women and is inherited exclusively from mothers.
Researchers combed GenBank, the National Institutes of Health genetic sequence database, and earlier scientific publications for scans of Native American mitochondrial lineages and added previously unpublished sequences to this work, said study co-author Ugo Perego, director of operations at SMGF. The genetic sequences are pan-American, including native North, Central and South American populations.
"This is the first comprehensive overview of the principal pan-American branches of the Native American mtDNA tree," said Antonio Torroni, study co-author heading the University of Pavia group. Torroni is considered one of the fathers of genetic research on Native Americans and was the first to discover, 15 years ago, the four major genetic groups to which 95 percent of Native Americans belong.
The study released today identifies the six surviving Native American mtDNA lineages that are dated to approximately 20,000 years ago, designated as A2, B2, C1b, C1c, C1d and D1. Today's study also confirms the presence of five more rare, less known and geographically limited genetic groups: X2a, D2, D3, C4c and D4h3.
The five more rare genetic groups will help researchers isolate branches within the pan-American groups that are younger or come from a better-defined geographic area, said lead author Dr. Alessandro Achilli, researcher at the University of Pavia and assistant professor at the University of Perugia. "For example, we learned one branch is only found among Aleuts and Eskimos," he said. "The presence of these additional subgroups suggests different migratory events from Asia or the Bering Straits. This study will be used as a reference for all future research on Native Americans. It is essential for reconstructing the history of specific Native American groups and for reliable association studies between mtDNA haplogroups and complex disorders," said Achilli.
Comprehensive data from the study is available online at www.plos.org, said Perego, and may be used to improve tests by commercial genetic genealogy firms, such as GeneTree. GeneTree (www.genetree.com) is a DNA-enabled family history-sharing Website helping people understand where their personal histories belong within the greater human genetic story. GeneTree was developed by the Sorenson family of companies and draws on the expertise of the Sorenson Molecular Genealogy Foundation.
People are increasingly using genetic testing to learn about their roots, said Perego. "I receive calls and emails regularly asking, 'With a DNA test, can you prove I have Native American ancestry?' Our new research has the potential to fine-tune genetic genealogy tests for these people." He noted genetic testing is not currently accepted as proof of ancestry for admission into a tribe.
About Sorenson Molecular Genealogy Foundation
The Sorenson Molecular Genealogy Foundation (SMGF; www.smgf.org) is a non-profit research organization that has created the world's largest repository of correlated genetic and genealogical information. The SMGF database currently contains information about more than six million ancestors through linked DNA samples and pedigree charts from more than 170 countries, or approximately 90 percent of the nations of the world. The foundation's purpose is to foster a greater sense of identity, connection and belonging among all people by showing how closely we are connected as members of a single human family. For more information about the foundation's free, publicly available database, visit
http://www.smgf.org/.
See also:
http://download.ajhg.org/AJHG/pdf/PIIS0002929708001390.pdf
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