Sometime before 12,000 years ago, nomadic hunter-gatherers in the Middle East made one of the most important transitions in human history: they began staying put and took to farming.
A pair of ancient-DNA studies1,2 – including one of the largest assemblages of ancient human genomes yet published – has homed in on the identity of the hunter-gatherers who settled down.
Archaeological and genetic evidence suggests that humans first took to farming in the Middle East. This transition – which also later occurred independently in other parts of the world – is known as the Neolithic revolution, and is linked to the first domestic plants and animals.
Previous ancient-genomics studies3 have hinted at complex origins for Middle Eastern farmers, involving geographically distinct groups of hunter-gatherers with varying genetic legacies.
Europe’s first farming populations descend mostly from farmers in the Anatolian peninsula, in what is now Turkey. “What happened before they started to migrate and propagate farming into Anatolia and Europe?” asks Laurent Excoffier, a population geneticist at the University of Bern.
To tackle this question, a team co-led by Excoffier sequenced the genomes of 15 hunter-gatherers and early farmers who lived in southwest Asia and Europe, along one of the main migration routes early farmers took into Europe – the Danube River. The remains came from several archaeological sites, including some of the first farming villages in western Anatolia.
The researchers generated ‘high coverage’, or high-quality, genomes – a rarity in ancient-genomics work. This allowed them to plumb the data for demographic details, such as shifts in population size, that are ordinarily outside the remit of ancient-DNA studies based on less complete genomes.
Mix and match
Excoffier’s team found that ancient Anatolian farmers descended from repeated mixing between distinct hunter-gather groups from Europe and the Middle East. These groups first split around the height of the last Ice Age, some 25,000 years ago. Modeling suggests that the western hunter-gatherer groups nearly died out, before rebounding as the climate warmed.
Once established in Anatolia, Excoffier’s team found, early farming populations moved west into Europe in a stepping-stone-like fashion, beginning around 8,000 years ago. They mixed occasionally – but not extensively – with local hunter-gatherers. “It’s really the spread of people, of farming communities, that brought farming further west,” says Excoffier. The study is published in Cell on 12 May1.
The findings chime with those of an ancient-genomics study posted on the bioRxiv preprint server on 5 May2. A team co-led by palaeogeneticist Eske Willerslev at the University of Copenhagen sequenced the genomes of 317 hunter-gatherers and early farmers from across Eurasia, the largest-yet ancient genome study from this period. That study also finds an ancient split between eastern and western hunter-gatherer groups, and traces the arrival of Anatolian farmers in Europe, beginning around 8,700 years ago in the Balkans. Willerslev declined to comment on the study before it appears in a journal.
The studies reveal finer details of the dawn of farming that had previously been painted only in broad brushstrokes and based on small numbers of genomes of relatively low coverage, says Pontus Skoglund, a palaeogeneticist at the Francis Crick Institute in London. “Both of these papers are where ancient DNA needs to be next.”