Examining models of modern human origins through the analysis of 43 fully sequenced human Y chromosomes

Abstract

Over the past four decades, molecular studies have yielded two primary models for understanding the uniparental DNA phylogenetic trees of modern humans: the Out of Africa (OOA) and the Out of East Asia (OOEA) models. These models differ in their underlying assumptions, particularly in relation to early stem haplotypes, even though they share many haplotype relationships. Leveraging the wealth of new genetic variants unveiled through the comprehensive sequencing of 43 diverse human Y chromosomes, we here investigated the presence of shared variants among different haplotypes to determine which model better aligns with the genetic data. We validated our approach by confirming numerous well-established haplotype relationships that are consistent with both the OOA and OOEA models. Remarkably, our analysis revealed a compelling pattern: we were able to corroborate the existence of stem haplotypes specific to the OOEA model, but not those exclusive to the OOA model. For instance, we found that A0b and A1a shared the most variants with each other, aligning with the notion that both fall under the A00A1a stem haplotype of the OOEA model. So, it becomes evident that the genetic data obtained from the complete sequencing of the 43 newly analyzed human Y chromosomes lends robust support to the OOEA model as the more accurate representation of modern human origins.