quality:correction, information:classification, stylistic:style_transfer, structural:scholar_edition
Mitochondrial DNA

Haplogroup X genetic sequences diverged about 20,000 to 30,000 years ago to give two sub-groups, X1 and X2. X2's subclade X2a occurs only at a frequency of about 3% for the total current Indigenous population of the Americas. However, X2a is a major mtDNA subclade in North America; among the Algonquian peoples, it comprises up to 25% of mtDNA types. It is also present in lower percentages to the west and south of this area — among the Sioux (15%), the Nuu-chah-nulth (11%–13%), the Navajo (7%), and the Yakama (5%). The predominant theory for sub-haplogroup X2a's appearance in North America is migration along with A, B, C, and D mtDNA groups, from a source in the Altai Mountains of central Asia. Haplotype X6 was present in the Tarahumara 1.8% (1/53) and Huichol 20% (3/15)