Strong Amerind/white sex bias and a possible sephardic contribution among the founders of a population in northwest Colombia

Historical and genetic evidences suggest that the recently founded populati on of Antioquia (Colombia) is potentially useful for the genetic mapping of complex traits. This population was established in the 16th-17th centuries through the admixture of Amerinds, Europeans, and Africans and grew in rel ative isolation until the late 19th century. To examine the origin of the f ounders of Antioquia, we typed 11 markers on the nonrecombining portion of the Y chromosome and four markers on mtDNA in a sample of individuals with confirmed Antioquian ancestry, The polymorphisms on the Y chromosome (five biallelic markers and six microsatellites) allow an approximation to the or igin of founder men, and those on mtDNA identify the four major founder Nat ive American lineages. These data indicate that similar to 94% of the Y chr omosomes are European, 5% are African, and 1% are Amerind. Y-chromosome dat a are consistent with an origin of founders predominantly in southern Spain but also suggest that a fraction came from northern Iberia and that some p ossibly had a Sephardic origin. In stark contrast with the Y-chromosome, si milar to 90% of the mtDNA gene pool of Antioquia is Amerind, with the frequ ency of the four Amerind founder lineages being closest to Native Americans currently living in the area. These results indicate a highly asymmetric p attern of mating in early Antioquia, involving mostly immigrant men and loc al native women. The discordance of our data with blood-group estimates of admixture suggests that the number of founder men was larger than that of w omen.