Human evolution: ancient DNA steps into the language debate.

Abstract

Two studies of ancient human DNA reveal expansions of Bronze Age populations that shed light on the long-running debate about the origins and spread of Indo-European languages. See Article p.167 & Letter p.207 Was the Bronze Age of a period of major cultural changes because of circulation of ideas or because of large-scale migrations? The authors sequence and analyse low-coverage genomes from 101 ancient humans from across Eurasia to reveal large-scale population migrations and replacements during this time. Analyses indicate that light skin pigmentation was already frequent among Europeans in the Bronze Age but not lactose tolerance, indicating a more recent onset of positive selection on the latter trait than previously believed. The reported findings are also consistent with the spread of Indo-European languages during the Early Bronze Age reported on page 207 of this issue. David Reich and colleagues generated genome-wide data from 69 Europeans who lived between 8,000 and 3,000 years ago. Their analyses reveal that closely related groups of early farmers — different from indigenous hunter-gatherers — appeared in Germany, Hungary and Spain at around 8,000 to 7,000 years ago. At the same time Russia was inhabited by a distinctive population of hunter-gatherers with high affinity to a 24,000-year-old Siberian. By 6,000 to 5,000 years ago, a resurgence of hunter-gatherer ancestry had occurred throughout much of Europe, apart from in Russia. Western and Eastern Europe came into contact about 4,500 years ago, leaving traces of steppe ancestry in present-day Europeans. In addition to providing new insights into Neolithic population dynamics, these analyses lend support to the theory of a steppe origin of at least some of the Indo-European languages of Europe. The reported findings are also consistent with a study of 101 Bronze Age genomes reported on page 167 of this issue.