Population growth of human Y chromosomes: a study of Y chromosome microsatellites

TLDR

The study aims to model recent population growth on the human Y chromosome by estimating demographic parameters and the time to the most recent common ancestor using microsatellite variation. Using eight Y‑chromosome microsatellite loci, the authors fit a growth‑permitting model, testing multiple mutation schemes and jointly estimating mutation‑size variance and demographic parameters. The growth model fits most populations better than a constant‑size model, revealing a recent common ancestor around 120,000 years ago and strong expansion signals that suggest either a recent human expansion from a small ancestral population or selection on the Y chromosome.

Abstract

We use variation at a set of eight human Y chromosome microsatellite loci to investigate the demographic history of the Y chromosome. Instead of assuming a population of constant size, as in most of the previous work on the Y chromosome, we consider a model which permits a period of recent population growth. We show that for most of the populations in our sample this model fits the data far better than a model with no growth. We estimate the demographic parameters of this model for each population and also the time to the most recent common ancestor. Since there is some uncertainty about the details of the microsatellite mutation process, we consider several plausible mutation schemes and estimate the variance in mutation size simultaneously with the demographic parameters of interest. Our finding of a recent common ancestor (probably in the last 120,000 years), coupled with a strong signal of demographic expansion in all populations, suggests either a recent human expansion from a small ancestral population, or natural selection acting on the Y chromosome.