Complete Mitochondrial Genomes Reveal Neolithic Expansion into Europe

Qiaomei Fu,Svante Pääbo,Pavao Rudan,Johannes Krause,Carles Lalueza-Fox

doi:10.1371/journal.pone.0032473

Abstract

The Neolithic transition from hunting and gathering to farming and cattle breeding marks one of the most drastic cultural changes in European prehistory. Short stretches of ancient mitochondrial DNA (mtDNA) from skeletons of pre-Neolithic hunter-gatherers as well as early Neolithic farmers support the demic diffusion model where a migration of early farmers from the Near East and a replacement of pre-Neolithic hunter-gatherers are largely responsible for cultural innovation and changes in subsistence strategies during the Neolithic revolution in Europe. In order to test if a signal of population expansion is still present in modern European mitochondrial DNA, we analyzed a comprehensive dataset of 1,151 complete mtDNAs from present-day Europeans. Relying upon ancient DNA data from previous investigations, we identified mtDNA haplogroups that are typical for early farmers and hunter-gatherers, namely H and U respectively. Bayesian skyline coalescence estimates were then used on subsets of complete mtDNAs from modern populations to look for signals of past population expansions. Our analyses revealed a population expansion between 15,000 and 10,000 years before present (YBP) in mtDNAs typical for hunters and gatherers, with a decline between 10,000 and 5,000 YBP. These corresponded to an analogous population increase approximately 9,000 YBP for mtDNAs typical of early farmers. The observed changes over time suggest that the spread of agriculture in Europe involved the expansion of farming populations into Europe followed by the eventual assimilation of resident hunter-gatherers. Our data show that contemporary mtDNA datasets can be used to study ancient population history if only limited ancient genetic data is available.

Highlights

Archaeological evidence suggests that agrarian societies emerged in Western Asia around 11,000 years before present (YBP) [1] and rapidly spread reaching South Eastern Europe by approximately 9,000 YBP [2]
The mitochondrial DNA (mtDNA) sequences determined from early farmers and hunter-gatherers are less than 400 bp in length and their number is quite small (105 and 21, respectively), limiting the information that can be gained about population sizes and putative population expansions in the past
They would suggest that H-type mtDNAs experienced a recent population expansion while U-type mtDNAs experienced a much older population expansion

Summary

Introduction

Archaeological evidence suggests that agrarian societies emerged in Western Asia around 11,000 years before present (YBP) [1] and rapidly spread reaching South Eastern Europe by approximately 9,000 YBP [2]. The frequency of mtDNA haplogroups, defined by substitutions shared by related mtDNA types (Phylotree.orgmtDNA tree build 12), in early farmers across Europe [7,10,11,12,13] was found to be overall similar to those in modern Europeans (Figure 1, Figure S4, Figure S5), while pre-Neolithic huntergatherers appear to be quite distinct (Figure 1).

Results

Conclusion