Rare Chinese Allele Found Among Southwestern U.S. Hispanics and North Mexican Indians
Like about 5 percent of North Americans, Francesca Serrano was adopted and never knew her birth parents. Wishing to find out her ancestry, she took our DNA Fingerprint Plus, an autosomal test based on an analysis of STR frequencies that can suggest overall ancestry matches to world populations. The caseworker who prepared her report was amazed at all the apparent Chinese ancestry mixed with Hispanic and Native American.
Photo: A Chinese woman.
After delivering the report recently, we nervously interviewed Serrano, who works in an East Coast DNA diagnostic center. She explained that the results made perfect sense. She grew up in Colima, Mexico, and people often asked her, “Do you have any Asian going on in you?”
Taking a closer look at her 16-locus STR profile, we noticed several unusual alleles. We will focus on one of them in this report, a value of 9 at D16S539. Admittedly, this is only one tiny ray of light into the genomic inheritance of a person, but geneticists have proved the utility of examining single STRs like this.
Sioux Need Not Apply
A rather sensational article—if genetics literature can ever be considered crowd-inciting—appeared in 2007, when Kari Schroeder and her team at the Department of Anthropology, University of California, Davis, showed that a value of 9 at D9S1120 cropped up in sample profiles of 35.4% of North and South American Indians as well as “West Beringians.” This marker was later dubbed a “private allele” shared by the members of a small hunting party that crossed the Bering Land Bridge and spread through the Americas many, many moons ago (the “single entry” theory).
STRs mutate almost as slowly as mitochondrial DNA and can therefore be useful markers for deep ancestry (see our post, “Evolution and Ancestry: DNA Mutation Rates,” October 23, 2012). One must be careful, however, not to make too much of them. For instance, the Sioux and Jemez reported 0.0% frequency of the touted allele (see Schroeder et al., “Haplotypic Background of a Private Allele at High Frequency in the Americas,” Mol. Biol. Evol. 26/5  1003), but that doesn’t make them any less Indian than the others. Try telling any Lakota Sioux he is less Indian than the others.
In Hispanic people in the American Southwest, our allele (which we will call for the sake of convenience “the Serrano allele”) occurs in only 8% percent of the population. It is not even among the most common possible numbers on that location; a repeat of 11 occurs in 31%.
|Huichol Indians Chiapas||7.5|
Analysis and Conclusion
From these figures, we get a general picture of the Serrano allele running relatively high, though still a minority report, in Western Hispanics, Mexicans and Indians. It is highest in the Navajos (who are rumored to have migrated from Chinese Turkistan in historical times). It is about the same in Arizona Hispanics as Mexicans from Chihuahua. We have no data from Sonora or Sinaloa, unfortunately.
Although present at an average frequency of about 12% in American Indian populations, the Serrano allele reaches its highest level among the Salishan Indians of British Columbia, where it is 30%. In neighboring regions of Canada, indigenous people have only about 8% of it (Saskatchewan aboriginals).
Everything comes from somewhere, and the Serrano allele in terms of human history is no exception. Its frequency is low or entirely absent in European populations and extremely high in East Asian, where it is highest among the Atayal tribe of Taiwanese aborigines (52%). It is also elevated among the Evenks (one of Russia’s native peoples), the Japanese, Pacific Islanders and Koreans. It is about the same level in Central, North, Chaozhou, Sichuan, Cantonese and Singapore Chinese populations, about 25%.
Like all alleles it is found in Africa, the ultimate source of all present-day humans, in modest amounts, but in even scarcer quantities in all the populations between there and North Asia. It enjoyed an enormous expansion in China.
It averages only 2.4% in all Native Americans, showing it is an extremely rare allele for American Indians to have overall.
Serrano’s No. 1 match on the basis of her entire profile (13 loci) is Chinese Hui – Ningxia. In this homeland of the Tangut people which once formed part of the Xia Xian Empire, the value of 9 on this marker is modal, with a frequency of 30%.
What are we to make of a single allele that is relatively rare in Native Americans, even rarer in European, Middle Eastern and other populations, but modal in some Chinese populations, with an apparent ancient center of diffusion in Taiwan? We conclude that it just may be a vestige of Asian DNA from China’s ancient and medieval periods of history, not deep history tracing back to Siberia.
In our next post we will see if any confirmatory evidence comes from other avenues of investigation.