Y-chromosome mismatch distributions in Europe

Area of Science:

• Population genetics
• Human evolutionary studies
• Molecular anthropology

Background:

• Demographic events shape genetic diversity within populations.
• Y-chromosome and mitochondrial DNA (mtDNA) are powerful tools for inferring human demographic history.
• Previous studies often show contrasting patterns between Y-chromosome and mtDNA diversity.

Purpose of the Study:

• To investigate ancient demographic events using Y-chromosome genetic markers.
• To compare demographic inferences from Y-chromosome data with those from mitochondrial DNA.
• To understand the factors contributing to observed differences in genetic diversity patterns.

Main Methods:

• Analysis of 3,677 Y chromosomes from 48 European and Mediterranean populations using 11 biallelic markers.
• Examination of mismatch distributions and Tajima's test for Y-chromosome data.
• Simulation of coalescent processes to model population demographics.
• Comparison with European mitochondrial DNA data, including analyses with a reduced number of variable sites.

Main Results:

• Tajima's test was insignificant for most Y-chromosome samples, with multi-peaked mismatch distributions in 47 populations.
• These patterns contrast with typical mitochondrial DNA analyses, suggesting different demographic histories or selective pressures.
• Simulations and theoretical considerations indicated that the observed differences are not statistical artifacts of marker number.
• Y-chromosome data suggest a constant male population size with increasing female population size, or differing selection regimes.

Conclusions:

• The distinct mismatch distributions of Y-chromosome and mitochondrial DNA reflect different demographic histories and/or selective pressures.
• Maternally and paternally transmitted loci experience unique evolutionary forces.
• Further research with more Y-chromosome markers may be needed for robust comparisons.
• Ancient population dynamics significantly impacted sex-specific genetic lineages differently.