Table 3. Geographic information.

Region	No. of individuals	Ethnic group	Mean altitude	Longitude and latitude
Chamdo	7	Tibet	3500	28°5′–32°6′N, 93°6′–99°2′E
Lhasa	11	Tibet	3650	29°36′N, 91°06′E
Nagqu	1	Tibet	4500	29°55′–36°30′N, 83°55′–95°5′E
Shannan	2	Tibet	3700	27°08′–29°47′N, 90°14′–94°22′E
Shigatse	9	Tibet	4000	27°13′–31°49′N, 82°1′–90°20′E
Xianyang	29	Han	400	108°70′N, 34°33′E