Human Populations: Origins and Evolution

Abstract

We can reconstruct aspects of our shared history as Homo sapiens from the bones of ancestors who have lived and died over the past 200 000 years, from the archaeological traces they left behind, and from DNA. Fossil, archaeological and genetic evidence agree in showing that all living humans trace back their ancestry to Africa. Around 100 000 years ago, anatomically modern humans dispersed from there, eventually giving rise to all non‐African populations. The timing, the consequences and many details of the evolutionary processes accompanying such dispersion are still under investigation but can be inferred from patterns of genomic variation among individuals and populations, and from the study of ancient DNA. This way, we have been able to reconstruct aspects of human evolution and prehistory in a previously unconceivable detail. Open questions include the extent and consequences of Homo sapiens interactions with archaic human forms, the routes followed by the populations expanding out of Africa, and the often complex relationships between modern ethnic identities and genetic ancestry. Key Concepts Populations of anatomically modern human originated in Africa, probably not in a single place and not necessarily at the same time Despite human populations being much larger, the overall human genetic diversity is the lowest in all primates, and these small differences are mainly accounted for by individual differences within populations Variation has been observed at more than 20% of nucleotide sites in our 3.3 billion nucleotide‐pairs genome, but a typical genome differs from the reference human genome at 4.1–5.0 million sites, that is less than 0.2% of the total genome length In a typical genome, there are 2100–2500 structural variants, affecting another 0.8% of its total length African genomes harbour more diversity than those from any other continent, and a large share of the genetic diversity in these continents is represented by subsets of African alleles. Patterns of genetic resemblance in humans are far more complicated than any scheme of racial classification can account The Neandertal contribution to non‐African genomes is currently estimated between 1.5 and 2.1%, whereas Denisovan ancestry seems largely limited to Melanesian and Oceanian populations (4–6%) Research is in progress to establish whether models of single or multiple dispersals from Africa better account for current genome diversity