Both social and engineering factors must be further explored and scrutinized across the globe—as should notions of justice related to flooding impacts and responses.
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Edited by Montgomery Slatkin, University of California, Berkeley, CA, and approved November 18, 2015 (received for review September 18, 2015)
Significance
Modern Europe has been shaped by two episodes in prehistory, the advent of agriculture and later metallurgy. These innovations brought not only massive cultural change but also, in certain parts of the continent, a change in genetic structure. The manner in which these transitions affected the islands of Ireland and Britain on the northwestern edge of the continent remains the subject of debate. The first ancient whole genomes from Ireland, including two at high coverage, demonstrate that large-scale genetic shifts accompanied both transitions. We also observe a strong signal of continuity between modern day Irish populations and the Bronze Age individuals, one of whom is a carrier for the C282Y hemochromatosis mutation, which has its highest frequencies in Ireland today.
Abstract
The Neolithic and Bronze Age transitions were profound cultural shifts catalyzed in parts of Europe by migrations, first of early farmers from the Near East and then Bronze Age herders from the Pontic Steppe. However, a decades-long, unresolved controversy is whether population change or cultural adoption occurred at the Atlantic edge, within the British Isles. We address this issue by using the first whole genome data from prehistoric Irish individuals. A Neolithic woman (3343–3020 cal BC) from a megalithic burial (10.3× coverage) possessed a genome of predominantly Near Eastern origin. She had some hunter–gatherer ancestry but belonged to a population of large effective size, suggesting a substantial influx of early farmers to the island. Three Bronze Age individuals from Rathlin Island (2026–1534 cal BC), including one high coverage (10.5×) genome, showed substantial Steppe genetic heritage indicating that the European population upheavals of the third millennium manifested all of the way from southern Siberia to the western ocean. This turnover invites the possibility of accompanying introduction of Indo-European, perhaps early Celtic, language. Irish Bronze Age haplotypic similarity is strongest within modern Irish, Scottish, and Welsh populations, and several important genetic variants that today show maximal or very high frequencies in Ireland appear at this horizon. These include those coding for lactase persistence, blue eye color, Y chromosome R1b haplotypes, and the hemochromatosis C282Y allele; to our knowledge, the first detection of a known Mendelian disease variant in prehistory. These findings together suggest the establishment of central attributes of the Irish genome 4,000 y ago.
Footnotes
↵1L.M.C. and R.M. contributed equally to this work.
- ↵2To whom correspondence should be addressed. Email: dbradley{at}tcd.ie.
Author contributions: D.G.B. designed research; L.M.C. and R.M. performed research; E.M.M. contributed new reagents/analytic tools; L.M.C., R.M., M.D.T., and D.G.B. analyzed data; and L.M.C., R.M., E.M.M., M.D.T., J.M., B.H., and D.G.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The sequences reported in this paper have been deposited in the European Nucleotide Archive (project accession no. PRJEB11995).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1518445113/-/DCSupplemental.
Freely available online through the PNAS open access option.
http://www.pnas.org/preview_site/misc/userlicense.xhtmlNeolithic and Bronze Age ancient Irish genomes
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