The frequencies of Haplogroup O-M119 among various East Asian and Austronesian populations suggest a complex genetic history of the modern Han populations of southern China. Although Haplogroup O-M119 occurs only at an average frequency of approximately 4% among Han populations of northern China and peoples of southwestern China and Southeast Asia who speak Tibeto-Burman languages, the frequency of this haplogroup among the Han populations of southern China nearly quadruples to about 15-23%. The frequency of Haplogroup O-M119 among the Southern Han has been found to be slightly greater than the arithmetic mean of the frequencies of Haplogroup O-M119 among the Northern Han and a pooled sample of Austronesian populations. This suggests that modern Southern Han populations may possess a non-trivial number of male ancestors who were originally affiliated with some Austronesian-related culture, or who at least shared some genetic affinity with many of the ancestors of modern Austronesian peoples.