Multiple instances of ancient balancing selection shared between humans and chimpanzees

Area of Science:

• Evolutionary genetics
• Human genomics
• Population genetics

Background:

• Balancing selection, which maintains genetic variation over long periods, is considered rare in evolutionary history.
• Understanding the mechanisms that preserve genetic diversity is crucial for comprehending species adaptation.

Purpose of the Study:

• To identify instances of long-lived balancing selection across the genome.
• To investigate the evolutionary forces shaping genetic variation shared between humans and chimpanzees.

Main Methods:

• Genome-wide scan for shared single nucleotide polymorphisms (SNPs) and haplotypes between humans and chimpanzees.
• Analysis of noncoding and coding regions for evidence of ancestral polymorphism.
• Enrichment analysis of identified regions for specific gene functions.

Main Results:

• Identified 125 genomic regions with segregating haplotypes shared between humans and chimpanzees, beyond the major histocompatibility complex.
• Found evidence of ancestral polymorphism persisting in six regions.
• Observed significant enrichment of shared haplotype regions for membrane glycoproteins and related coding polymorphisms.

Conclusions:

• Ancient balancing selection has played a significant role in shaping human genetic variation.
• Genes involved in host-pathogen interactions are frequently targeted by this ancient balancing selection.
• The findings challenge the notion that long-term balancing selection is extremely rare.