An African-American man in South Carolina has lineage tracing back 338,000 years, according to a new study. The unidentified man’s Y chromosomes — a hereditary factor determining male gender — has a history so old that it predates the age of the oldest known Homo sapiens fossils, according to the report published in the American Journal of Human Genetics.
The man’s chromosome carries a rare mutation, which researchers matched to a similar chromosome in the Mbo, a population living in a tiny area of western Cameroon in sub-Saharan Africa. “Our analysis indicates this lineage diverged from previously known Y chromosomes about 338,000 ago, a time when anatomically modern humans had not yet evolved,” Michael Hammer, associate professor at the Univ. of Arizona’s Department of Ecology and Evolutionary Biology and a research scientist at the UA’s Arizona Research Labs, said via a press release. “This pushes back the time the last common Y chromosome ancestor lived by almost 70 percent.”
The DNA study began after the South Carolina man submitted a small tissue sample to theNational Geographic Genographic Project. Researchers were shocked after they noticed none of the genetic markers used to assign lineages to known Y chromosome groupings were found. The man’s DNA sample was sent to Family Tree DNA for sequencing. Fernando Mendez, a postdoctoral researcher in Hammer’s lab, led the effort to analyze the DNA sequence. It included more than 240,000 base pairs of the Y chromosome. Searches through a huge database led to the Mbo connection.
The scientists were then able to estimate the emergence of the chromosome mutation based on rates of change, creating a sort of “family tree” for the chromosome. The discovery doesn’t necessarily mean that all humans descended from an ancestor living in western Cameroon. “It is a misconception that the genealogy of a single genetic region reflects population divergence,” Hammer explained. “Instead, our results suggest that there are pockets of genetically isolated communities that together preserve a great deal of human diversity.”
Hammer added that still “It is likely that other divergent lineages will be found, whether in Africa or among African-Americans in the U.S. and that some of these may further increase the age of the Y chromosome tree. There has been a lot of hype with people trying to trace their Y chromosome to different tribes, but this individual from South Carolina can say he did it.” The study has even further implications. It strengthens the belief that there is no “mitochondrial Eve” or “Y chromosome Adam.” All of humankind, as a result, did not descend from exactly one pair of humans that lived at a certain point in human evolution.
Maria Lloyd (@WritingsByMaria) is the Business Manager for the Your Black World Network. She is a graduate of Clark Atlanta University and an advocate of dismantling the prison industrial complex, increasing entrepreneurship, reforming education, and eradicating poverty.