Hunter-gatherer admixture facilitated natural selection in Neolithic European farmers

Unveiling recent and ongoing adaptive selection in human populations

“…Moreover, the observed allele frequencies and ancestry fractions at these pigmentation-associated variants in later admixed populations significantly deviated from neutral expectations, suggesting subsequent selection during the Neolithic, Bronze Age, and historical periods [ 33 – 35 ]. These findings point to continued selective pressure for light pigmentation over the past 2,000 years in west Eurasia and support the concept that admixture may facilitate rapid adaptation by introducing advantageous alleles [ 34 – 37 ].…”

“…If all or most trait-influencing variants can be identified in an unbiased manner, signals at these loci can be interrogated jointly to uncover selection on the trait. The most straightforward idea for detecting polygenic adaptation is to directly combine GWAS results and population genetic summary statistics (e.g., some in Fig 2C) [15,19,[33][34][35]69]. Common approaches include tests for shifts in distribution of single-locus summary statistics indicative of selection (e.g., F st ) at GWAS hits [69] or correlation between GWAS summary statistics (such as effect direction, magnitude, and significance level) and population genetic summary statistics.…”

“…Common approaches include tests for shifts in distribution of single-locus summary statistics indicative of selection (e.g., F st ) at GWAS hits [69] or correlation between GWAS summary statistics (such as effect direction, magnitude, and significance level) and population genetic summary statistics. This approach has been applied to both present-day and ancient DNA data, and several studies explicitly leveraged population admixture events in recent human history to gain insights into the timing of selection [15,19,[33][34][35]70]. Overall, these studies found consistent evidence of selection on variants underlying anthropometric, pigmentation, and immune-related trait variation in human populations in the past 10,000 years.…”

“…The derived alleles associated with lighter skin or eye color at several pigmentation-associated genes exhibited distinct frequencies in different ancestral populations, potentially reflecting differential selective pressures across geography prior to the Mesolithic period (i.e., before 9,000 to 10,000 years ago) [31,32]. Moreover, the observed allele frequencies and ancestry fractions at these pigmentation-associated variants in later admixed populations significantly deviated from neutral expectations, suggesting subsequent selection during the Neolithic, Bronze Age, and historical periods [33][34][35]. These findings point to continued selective pressure for light pigmentation over the past 2,000 years in west Eurasia and support the concept that admixture may facilitate rapid adaptation by introducing advantageous alleles [34][35][36][37].…”

“…Significant variation in selection strength has also been found at several other previously identified selected loci [ 39 ]. Overall, ancient DNA studies have confirmed selection signals near multiple genes associated with diet, pigmentation, and immune response revealed in modern genomic data, and have provided fine-resolution insights into the temporal dynamics and geographic distribution of the selected variants and the corresponding selection strengths [ 26 , 34 , 39 , 40 ].…”