Admixture with indigenous people helps local adaptation: admixture-enabled selection in Polynesians

Area of Science:

• Population Genetics
• Human Evolution
• Genomics

Background:

• Human populations have undergone numerous admixture events throughout history.
• Polynesians represent a unique case of admixture between Austronesian (Asian-related) and indigenous Near Oceanian (Papuan-related) ancestors.
• Investigating Polynesian genomes offers insights into how admixture influences local adaptation.

Purpose of the Study:

• To estimate local ancestry across the Polynesian genome.
• To identify genomic regions showing evidence of admixture-enabled selection from Papuan-related ancestors.
• To understand the role of admixture in the rapid local adaptation of Polynesian populations.

Main Methods:

• Local ancestry estimation was performed on the genomes of 23 Tongan subjects.
• Genomic regions with significantly enriched Papuan-related ancestry were identified.
• Coalescent simulations and approximate Bayesian computation were used to infer selection.

Main Results:

• Papuan-related ancestry constituted a mean of 24.6% of the Polynesian genome.
• The extended Major Histocompatibility Complex (xMHC) and the ABCC11 gene showed significant Papuan-related ancestry enrichment (>5 SD above mean).
• Positive selection was detected in the ABCC11 gene (rs17822931 SNP) in Polynesian ancestors, driven by Papuan-related ancestry.

Conclusions:

• Admixture with Papuan-related ancestors facilitated rapid local adaptation in Polynesian populations.
• Admixture-driven acceleration of local adaptation is likely a common phenomenon in human evolutionary history.
• Genomic studies of admixed populations are crucial for understanding human adaptation.