It just came out in Nature Human Behaviour a new paper to which I collaborated: Climate shaped how Neolithic farmers and European hunter-gatherers interacted after a major slowdown from 6,100 BCE to 4,500 BCE. The article is behind paywall, but there is a read-only version, and the publisher added the full text in Researchgate.
The Neolithic transition in Europe was driven by the rapid spread of Near Eastern farmers who, over a period of 3,500 years, brought food production to the far corners of the continent. However, this wave of expansion was far from homogeneous, with a marked slowdown observed at higher latitudes, which could be related to the different climatic conditions encountered by Neolithic farmers as they moved.
We tested this hypothesis. First, we calculated the expansion routes in the various areas using a large database collating archaeological dates of the first arrival of agriculture throughout Europe. We have identified four of them, shown in the image below.
Along three of these routes, we observed a slowdown (thicker lines in the image) where the value of Growing Degrees Days (reflects the quality of the growing season) exceeds a certain threshold (light green in the map). This suggests that crops that originated in the Near East may have struggled to grow in harsher climatic conditions, not allowing Neolithic populations to produce enough to support population increase and/or expansion.
Furthermore, the study of ancient DNA shows us that in conjunction with the same threshold in growing degree days, the level of admixture between farmers and hunter-gatherers increases, suggesting that unreliable harvests in these regions may have favoured the contact between the two groups.
Lia Betti, Robert M. Beyer, Eppie R. Jones, Anders Eriksson, Francesca Tassi, Veronika Siska, Michela Leonardi, Pierpaolo Maisano Delser, Lily K. Bentley, Philip R. Nigst, Jay T. Stock, Ron Pinhasi & Andrea Manica
Climate shaped how Neolithic farmers and European hunter-gatherers interacted after a major slowdown from 6,100 BCE to 4,500 BCE
The Neolithic transition in Europe was driven by the rapid dispersal of Near Eastern farmers who, over a period of 3,500 years, brought food production to the furthest corners of the continent. However, this wave of expansion was far from homogeneous, and climatic factors may have driven a marked slowdown observed at higher latitudes. Here, we test this hypothesis by assembling a large database of archaeological dates of first arrival of farming to quantify the expansion dynamics. We identify four axes of expansion and observe a slowdown along three axes when crossing the same climatic threshold. This threshold reflects the quality of the growing season, suggesting that Near Eastern crops might have struggled under more challenging climatic conditions. This same threshold also predicts the mixing of farmers and hunter-gatherers as estimated from ancient DNA, suggesting that unreliable yields in these regions might have favoured the contact between the two groups.
Nat Hum Behav (2020). https://doi.org/10.1038/s41562-020-0897-7