A Tale of Two Lineages
The Mosuo people, residing near Lugu Lake in China's Yunnan province, practice a matrilineal and matrilocal lifestyle that sets them apart. In this society, heritage and property descend through the female line, and women remain in their maternal homes after marriage. This unique social structure, particularly the practice of "walking marriages" where men visit their wives at night but reside and work in their own mothers' homes, has changed the Mosuo gene pool.
Genetic investigations show a difference between the maternal and paternal lineages of the Mosuo. Studies analyzing mitochondrial DNA (mtDNA), which is inherited exclusively from the mother, show that the Mosuo's maternal lines are most similar to those of the neighboring Naxi and Pumi peoples. This suggests a shared female ancestry among these groups. Six major mtDNA haplogroups—B4, B5a, C, D*, D5a, and F1b—account for over 80% of the Mosuo maternal lineages.
The paternal story, read from the Y chromosome, is quite different. Mosuo paternal lineages show a stronger resemblance to those of the local Tibetan population. This genetic asymmetry—maternal heritage linked to one group and paternal to another—reflects their social customs. The matrilocal system means that while women and their mtDNA stay put, men from other groups, like the Tibetans, have historically integrated into the Mosuo population, introducing their Y chromosomes.
Genetic Clues to Cultural History
Researchers have examined specific genetic markers to understand these patterns more deeply. Analysis of the Y chromosome involved typing 13 Single Nucleotide Polymorphisms (SNPs) and 8 Short Tandem Repeats (STRs). One of the most frequent Y-SNP haplotypes found among the Mosuo is H8, which is also prevalent in Yunnan Tibetans, appearing in 31.9% of Mosuo males and 34.0% of the Tibetan sample group. Another significant haplotype, H5, is present in 23.4% of Mosuo men but is far less common in surrounding populations, except for the Naxi (37.5%).
The study of mtDNA diversity also shows the history of Mosuo matrilocality. Typically, in a matrilocal society where women do not move, one would expect to find lower mtDNA diversity compared to neighboring patrilocal groups where women do move. However, the Mosuo show comparable levels of mtDNA haplotype diversity. This finding suggests that the practice of matrilocality among the Mosuo is not ancient, likely having begun several thousand years ago, after the Paleolithic Age. The genetic data, therefore, confirms the effects of their social system and provides a rough timeline for its origin.