Sequences From First Settlers Reveal Rapid Evolution in Icelandic mtDNA Pool

Agnar Helgason,Unnur Þorsteinsdottir,Kári Stefánsson,Adam Baker,Shyamali Ghosh,Lilja Árnadóttir,Elena Gigli,Maria Lourdes Sampietro,Sigrún Sigurðardóttir,Jaume Bertranpetit,Carles Lalueza-Fox,Gil Mcvean

doi:10.1371/journal.pgen.1000343

Agnar Helgason, Unnur Þorsteinsdottir + Show 10 more

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https://doi.org/10.1371/journal.pgen.1000343

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Abstract

A major task in human genetics is to understand the nature of the evolutionary processes that have shaped the gene pools of contemporary populations. Ancient DNA studies have great potential to shed light on the evolution of populations because they provide the opportunity to sample from the same population at different points in time. Here, we show that a sample of mitochondrial DNA (mtDNA) control region sequences from 68 early medieval Icelandic skeletal remains is more closely related to sequences from contemporary inhabitants of Scotland, Ireland, and Scandinavia than to those from the modern Icelandic population. Due to a faster rate of genetic drift in the Icelandic mtDNA pool during the last 1,100 years, the sequences carried by the first settlers were better preserved in their ancestral gene pools than among their descendants in Iceland. These results demonstrate the inferential power gained in ancient DNA studies through the application of population genetics analyses to relatively large samples.

Highlights

The Icelanders are one of the most studied populations in human genetics [1,2,3,4,5]
We show that the ancient Icelandic mitochondrial DNA (mtDNA) sequences are more closely related to sequences from contemporary inhabitants of Scotland, Ireland, and Scandinavia than to those from the modern Icelandic population
It appears that the array of sequences carried by the first generations of Icelanders was better preserved in the gene pools of their ancestors than among their modern descendants because of a faster rate of evolution due to genetic drift in the Icelandic mtDNA pool during the last 1,100 years

Summary

Introduction

The Icelanders are one of the most studied populations in human genetics [1,2,3,4,5]. Studies of mtDNA variation indicate that contemporary Icelanders trace about 37% of their matrilineal ancestry to Scandinavia, with the remainder coming from the populations of Scotland and Ireland [1,8,9]. As each gene pool was affected by a combination of evolutionary forces during the intervening time, the ancestry of the admixed population may have been considerably altered at any particular locus. There is evidence for relatively high levels of genetic drift in this population due to its small size [2,10]

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