The human family tree and the Neandertal branch

TL;DR

This paper models genetic distances in a large, asexually reproducing population, revealing complex, non-trivial properties that could inform debates on human origins, especially regarding Neandertal and modern human relationships.

Contribution

It introduces a novel theoretical framework for understanding genetic distance distributions in large populations without selection, applicable to human evolutionary studies.

Findings

Distances are highly non-trivial and random in the population.

Mean distances vary over time, even in large populations.

Results scale linearly with population size.

Abstract

We consider a large population of asexually reproducing individuals in absence of selective pressure. The population size is maintained constant by the environment. We find out that distances between individuals (time from the last common ancestor) exhibit highly non trivial properties. In particular their distribution in a single population is random even in the thermodynamical limit. As a result, not only distances are different for different pairs of individuals but also the mean distance of the individuals of a given population is different at different times. All computed quantities are parameters free and only scale linearly with the population size. Results in this paper may have some relevance in the 'Out of Africa/ Multi-regional' debate about the origin of modern man. In fact, the recovery of mitochondrial DNA (mtDNA) from Neandertal fossils in three different loci: Feldhofer (Germany), Mezmaiskaya (Northern Caucaso), Vinjia (Croatia), permitted to compare Neandertal/Neandertal distances with Neandertal/modern and modern/modern ones.