As the world’s largest ethnic group, the genetic landscape of Han Chinese had been widely concerned during the last decades. Previous studies based on mitochondrial DNA (mtDNA) variants indicated a north-south maternal genetic divergence among Han populations. However, these studies mainly based on low-resolution mtDNA data of relatively limited samples, making the maternal genetic landscape, as well as the forces shaping the genetic structure of this ethnic group remain unclear until nowadays. 

A team of scientists from the Kunming Institute of Zoology, Chinese Academy of Sciences (KIZ, CAS) and Chengdu 23 Mofang Biotechnology Co., Ltd recently carried out an intensive investigation of genetic landscape of Han Chinese. Based on mtDNA high-resolution genotyping data (4,004 SNPs) of more than 21 thousand samples from 33 of the 34 administrative regions in China, they identified a general north-south genetic divergence among Han populations. Additionally, they found a much more significantly genetic differentiation existing among Han populations residing in different river valleys, especially those from the three major river valleys (i.e. Yellow river, Yangtze river and Zhujiang river valleys). 

Further analyses indicated that haplogroups D4, B4 and M7 contributed most to the three river clusters, respectively. Age estimation suggested most of their lineages can be traced back to the early Holocene period (5-11.5 kilo years ago (kya)).

This would be attributed to the climate improvement as well as the origination (or expansion) of three ancient agricultures along the different river valleys during this period, viz. the millet agriculture (Yellow river), rice agriculture (Yangtze river), and tropical agriculture (Zhujiang river). Concordantly, rapid population growths along the three river valleys were also observed since the beginning of Holocene era. 

These evidence indicated that that the maternal gene pools of contemporary Han Chinese populations have retained more genetic imprint of early Neolithic farmers from different regions, thus highlighting the important roles of the three ancient agricultural traditions played in shaping the genetic landscape of Han Chinese. 

This work was published on Molecular Biology and Evolution. Dr. LI Yuchun (Assistant Professor at KIZ), YE Weijian and JIANG Chuangui (23 Mofang Biotechnology Co., Ltd) are co-first authors of this work. Dr. KONG Qingpeng (Professor at KIZ) is corresponding author. This work was supported by grants from fromthe National Natural Science Foundation of China, Strategic Priority Research Program and Key Research Program of Frontier Sciences of Chinese Academy of Sciences, National Key R&D Program of China, Yunnan Applied Basic Research Project, CAS “Light of West China” Program, and National Natural Science Foundation of China.

(By LI Yuchun)