Interesting paper, 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.
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.
“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.”
True, though can’t only be reason for HG introgression in N Europe, as Iberia and N Africa have a lot (maybe more) from locals too.
I guess there’s the question of how good different climates were for Mesolithic HG strategies as well go consider.
NW Europe relatively tough going for Near East crops… But also not likely to have a huge population of HG, so it balances, and as incomers probably already switched package a bit (more dairy; less cereal) less introgression of local HG than seen in Southern France and Spain. Baltic by contrast is worse for farming (+ probably even dairy) can support large semi-sedentary fisher population. So…
Mesolithic HG strategies in Europe may have also been a bit optimized for the south, from where they came out of mainly probably Italian and Balkan refugia. Sometimes these worked well in north (rich fishing in some places), probably in some places less well.
Interesting segment of paper: The establishment of cereal cultivation in the British Islands and Scandinavia, around 4,600-4,000 bce (refs. 38–40), is followed by a sharp decrease and even disappearance of cereals from the archaeological record for several centuries, suggesting that their yield might not have been enough, or might have been too unpredictable, to support the local populations.”
This is the “4th Millennium BCE Farming Failed” argument that I associate with Dorian Fuller’s work.
Where cereal cultivation continued, such as in some Scottish islands and part of Scandinavia, there was a marked shift towards the use of barley, which is more resilient to cold temperatures and general stress.”
And Orkney becomes an apparent center of cultural diffusion in Britain – innovation on the margin once again sets the conditions for a later, surprising, cultural centrality (as happens sometimes in history).
“The original Neolithic package included cereals that are planted in autumn and harvested in summer. Instead, spring varieties of barley are cultivated today in northern latitudes, planted in spring and harvested in autumn, with no need to survive the harsh winters of Northern Europe. It is possible that the original winter varieties were not well suited to the
colder and wetter climate of Northern Europe, and that agriculture started thriving in the British Isles in the Early Bronze Age because of the introduction of spring varieties.
The post-Beaker bounceback of farming in BI.
This sets up the interesting possibility that expanding groups with Steppe ancestry adopted spring varietals from temperate Neolithic societies in East-Central / SE Europe (Globular Amphora, other groups). Then expanded to NW Europe as more productive farmers.
E.g. rather than Beaker into Britain being pastoralists expanding over farmers, it may have been exactly the opposite (agro-pastoralist cereal farmers expanding over dairy pastoralists)… And potentially Beaker didn’t absorb many Brit late Neolithic pastoralists mainly just because not so many of them about.
Interesting that the term Central Europe is still applied to what is obviously Western Europe.
Something very similar happened in North America where the three sisters crops (maize, beans and squash) developed in Meso-America expanded to what is now the U.S. after a long delay until about 900 CE when the crops were finally adapted to the more northern climate.
@andrew, yeah, that’s linked with the “sudden burst of Cahokia parallels corn” hypothesis/finding from a couple months back – https://phys.org/news/2020-05-cahokia-parallels-onset-corn-agriculture.html
Another somewhat similar in theme paper at the same time was the proposal that the 4.2kya event drove rice farmers to change plant selection, ultimately allowing the frontier of demic diffusion to expand – https://www.sciencedaily.com/releases/2020/05/200515115646.htm
It seems like there may have been a few cases in pre-history where farming expanded to a kind of mixed strategy and low yield equilibria at the frontier that sometimes did (and sometimes did not) allow HG populations opportunity to catch up… Then a burst of growth happens when crops are properly adapted for local conditions.
This looks like nothing so much as classical `fractal fingers’ diffusion
https://www.nature.com/articles/s41598-019-43728-z
seen in many systems of diffusion under pressure (eg salt water pumped into
exhausted oil wells or emigration into the city from the countryside (when
people group themselves with previous migrants)).
Quick test on rate of HG introgression over time. Eurogenes blog has a big PCA datasheet for West Eurasia that includes lots of predominantly Barcin related samples about 484*. I’ve got the dates for these as well.
Take these and run a model using (https://vahaduo.github.io/vahaduo/) with (Barcin_N, Levant_N, WHG, EHG, CHG, IRN_N), and then combine EuroHG (EHG+WHG) and correlate with time.
Output: https://imgur.com/a/ZjQg1V9
The regression of EuroHG ancestry against time indicates increase in EEF related populations of 0.005% EuroHG ancestry per year, beginning in 6693 BCE. Assuming 30 years in a generation, that means 0.15% per generation, or that 1/666 reproductive events (that contributed to next generation) were EuroHG+Farmer, on average (in reality more pulse like, some times many more than 1/666, sometimes far fewer).
Separating out the earlier Neolithic regions (https://imgur.com/a/xrkUaSp) and later (https://imgur.com/a/VuXALou) to try and account for that. Different fits for later/earlier regions.
Non-linear fits suggest that as expected most profiles stablized by 4000-3000 BCE (after faster rate of change from 5500-4000 BCE). (Still, even in “most HG” EEF regions with, if going from 0%->25% HG over 1500 years is 50 generations, so only 1/200 reproductive events of “pure EuroHG”+farmer per generation…).
*I selected these 484 by eye, but only a handful had over 10% CHG, so they probably mostly lack significant “steppe” (except *maybe* a couple Bulgarian and late Iberian samples).
I read that the Indian-Settler boundary shifted 50 miles eastward in Texas in immediately after the Civil War.