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.
This is not a surprising result. I predicted this (along with many others) pattern in the late 2000s. It was just not plausible that a ‘spherical cow’ diffusion process characterized the expansion of farming. There is real topography and climate to deal with.
Jared Diamond’s Guns, Germs, and Steel comes in for a lot of criticism, but the insight of latitudinal migration being easier than longitudinal has been pretty spot-on. These authors find Neolithic expansion across the Mediterranean much faster and easier to model than that going north. Pretty clearly the Near Eastern farming cultural package was a poor fit to Northern Europe, and it took some adaptation for it to get good.
That being said, I think another aspect which is going to be impossible to model in a specific sense, is that there were political and social reasons for how and when these Neolithic lifestyles spread. To give a strange analogy, the massive internal war in the Arab Empire in the late 7th century gave Byzantium a major respite from external pressure and allowed it to recover. It’s totally plausible that chaos in a Neolithic tribal confederacy might give hunter-gatherer clans time to recover and retaliate.