Genomic diversity and structure among South and East Asian human populations

Abstract

Genetic variability is a complex concept that is affected by many factors. Studying the genetic variability within the human population provides a better understanding of how populations evolve. The genetic variability within modern humans resulted from different conditions experienced in different routes used by out of Africa migrations to other parts of the world. These events included mating with other human species (Neanderthals and Denisovans) and the development of cultural practices as they arrived in other parts of the world. Asia is more diverse in terms of physical geography, cultures, and languages, which makes it an interesting region to study human population genetic diversity and population structure. From animal studies, colonization of islands is often associated with loss of genetic diversity resulting in isolation. Although humans can easily move around, various aspects could result in isolation between populations. To test the concept of low genetic variability in island populations, I used 1000 genomes project variant calls datasets (autosomal, X-chromosome, Y-chromosome, and mitochondrial data), which include 983 individuals from ten Asian populations. I estimated the genetic diversity from autosomal dataset of South and East Asian populations to compare the genetic affinities between mainland and island populations. Reduced levels of genetic diversity were observed in Japan suggesting a possible genetic bottleneck during the initial colonization of the island. Despite the diverse cultural practices and South Asia being colonized early the populations are not more internally structured nor more genetically diverse compared to East Asia. Most East Asian populations had higher heterozygosity compared to South Asian populations. It is clear from the results that physical geography plays a crucial role in shaping the genetic diversity between populations. Significant levels of gene flow were observed between populations that are at close geographical distance compared to populations at distant proximity.