ADNA sample from an African-American living in South Carolina revealed that the human Y chromosome may be much older than previously thought— pushing back the most recent common ancestor for the Y chromosome lineage tree by almost 70 percent to around 338,000 years ago. The Y chromosome is the hereditary factor determining the male sex; because it does not exchange genetic material with other chromosomes, it is easier to trace the ancestral relationships between lineages. After analysis, it was shown that this may be the oldest known branch of the human Y chromosome—a new divergent lineage that apparently branched from the Y chromosome tree even before the first appearance of anatomically modern humans in the fossil records.