Modeling the contrasting Neolithic lineage expansions in Europe and Africa
The Neolithic transition refers to a change from a hunter-gatherer society to an agricultural society. Transitions in Europe and Africa caused a large increase in population size. When studying prehistory of the population, genealogical data can be helpful. Tests of ancient DNA show a discontinuity between European hunter-gatherer and early-farmer mitochondrial DNA (mtDNAs), suggesting that most lineages come during or after the Neolithic era. The Y chromosome does not recombine, so it provides a unique phylogenetic tree for male events. Another study used coalescent simulations of Y chromosomes to suggest an effective population expansion from 2 to 9500 males over about 325 years in Europe and an expansion from 40 to 2000 male over about 12000 years in Africa. Here we use coalescent simulations to investigate the effect of narrow bottlenecks and subsequent expansions on diversity in the sex chromosomes, autosomes, and mtDNA for different initial male to female ratios. We hope to find parameters that lead to calculated diversity ratios that match those in the current human population. We will also look at site frequency spectra, which will show how often rare mutations occur as a result of the bottleneck and expansion.