NEW YORK — Members of the present-day Muwekma Ohlone Tribe in California share genetic ancestry with individuals who lived in the same region hundreds and even thousands of years ago, a new study has found.
The result contrasts with previous studies based on analyses of artifacts and linguistics that indicated the Muwekma Ohlone migrated to the region 1,500 to 1,000 years ago, according to the authors, led by researchers at Stanford University and the University of Illinois at Urbana-Champaign.
In response to a request from and in partnership with the Muwekma Ohlone Tribal Council, they sequenced the genomes of 12 ancient individuals uncovered at two archaeological sites in the San Francisco Bay Area alongside the genomes of eight present-day tribal members. By comparing the ancient and modern genomes to each other and to previously sequenced samples from other populations, the researchers uncovered evidence of genetic continuity in the area stretching back nearly 2,000 years, as they reported Monday in the Proceedings of the National Academy of Sciences.
"The Ohlone living today who participated in the study may not be direct descendants of the ancient people whose genomes we sequenced, but the analysis suggests they descended from the broader population to which those ancient people belonged," co-senior author Noah Rosenberg, a professor of population genetics and society at Stanford University, said in a statement.
The ancient samples the researchers analyzed were uncovered at two sites in the southeast San Francisco Bay Area, one of which, the Síi Túupentak site, dates back to 100 to 600 years ago and the other, the Rummey Ta Kuččuwiš Tiprectak site, to 175 to 2,440 years ago. The researchers sequenced the genomes of 12 ancient individuals: eight from Síi Túupentak who lived between 184 to 601 years ago, based on carbon dating, and four from Rummey Ta Kuččuwiš Tiprectak who lived 1,826 to 1,905 years ago.
The analysis also included eight present-day tribal members in conjunction with previously published data on 68 ancient and 223 present-day individuals from across Asia, Europe, North America, and South America.
In a principal components analysis, the European samples clustered together, as did the Siberian, Alaskan, and Greenland samples and the Californian, Nevadan, Mexican, and Central and South American samples. Zooming in on the last cluster, the researchers noted that the samples fell in part along a south-to-north cline, starting from South America and reaching to Nevada. Further, the ancient individuals in the analysis from the Bay Area and from Southern California overlapped.
Unsupervised clustering split the ancient California individuals into a group centered on Southern California and one from the Bay Area, which also included modern Muwekma Ohlone individuals.
Additional identity-by-state segment sharing analyses further pointed toward four clusters of the ancient individuals: Nevada, the Bay Area, the North Channel Islands and Santa Barbara, and the South Channel Islands.
Within the Bay Area samples, the researchers noted high levels of sharing of genetic regions between ancient and modern samples, to a higher degree than with the other groups. This suggested that there has been genetic continuity in the area. An admixture analysis additionally underscored the shared ancestry between the modern Muwekma Ohlone individuals and the individuals from the Síi Túupentak and Rummey Ta Kuččuwiš Tiprectak sites.
"We were able to find one ancestral component from their genomic analysis that was shared with ancient people from the Bay Area," Rosenberg said.
The researchers added that the study was done in partnership with the Muwekma Ohlone. "This was a rare, collaborative, community-engaged research project, with tribal members and archaeologists working side by side for more than a year of fieldwork, resulting in a tremendous repatriation of knowledge to the descendent community," coauthor Brian Byrd from the Far Western Anthropological Research Group said in a statement.