If you've ever wondered how farming spread far and wide, our research on past human societies offers one explanation: contact between different groups often drives change.
Authors
- Javier Rivas
Senior Lecturer in Economics, University of Bath
- Alfredo Cortell
Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology
In a recent paper , together with our colleagues Enrico R. Crema, Stephen Shennan and Oreto García-Puchol among others, we used a mathematical model to analyse what happens when communities with different cultures interact.
We used a model from predator-prey equations that usually describe how animal populations compete. Our results, published in Proceedings of the National Academy of Sciences, showed that when one group of foragers and another group of farmers share the same space, their interaction can determine the speed at which agriculture is adopted.
In many parts of the world, people lived by hunting, fishing and gathering until groups of farmers arrived. This date varies depending on region. For instance, farming arrived at around 1000BC in Japan but at around 5600BC in Iberia.
Archaeologists have long debated whether farming spread because local foragers took it up themselves or because farmers from elsewhere moved in and outnumbered or replaced them.
Our model builds on the view that in some cases locals might have adopted farming from newcomers either through exchange or intermarriage but in other cases they might have been displaced or killed by the incoming farmers.
We tested simulated data against real data from Eastern Iberia, Denmark and the island of Kyushu (Japan) to see which explanations fit best. Considering a period of 1,000 years, we combined equations for population growth, mortality resulting from species' competition, migration and something called an assimilation parameter, which represents how many foragers became farmers in each time step.
This allowed us to assess the role of competition and collaboration between groups during the transition to farming.
To check whether this theory makes sense in real life, we looked at three regions where farming was introduced to local foragers.
1. Eastern Iberia (Spain)
Agriculture seems to have arrived around 5600-5500BC in this area and took hold relatively quickly, within about 300-400 years. Small groups of farmers probably arrived by sea , which meant weaker ties to their original communities.
As a result, they had only two options: perish or expand, since they could not rely all that much on the support of their original groups. Their attempt to expand farming may have failed if they didn't integrate with or eliminate locals.
This opens the door to potential "failed attempts", not captured by the archaeological record. There are recorded "failed" attempts at farming in other areas throughout the world in the archaeological record.
2. Denmark
Further north, the process was slower, taking up to 600-800 years. Farmers and foragers appear to have lived close to one another for centuries before the rapid turnover, with a stable "frontier" between the two groups for centuries.
3. Kyushu (Japan)
Wet rice farming was introduced by multiple waves of migrants from the Korean peninsula around 1,000BC. We found that, although the farming population grew at a modest rate, mixing with locals was limited. Foragers did, however, decline faster and grow slower than in the other two areas.
Why contact matters
Our findings show how human interaction can drive the adoption of farming. Our approach considers that small-scale human relationships can have big consequences.
Imagine a small community of farmers setting up near a river that local hunter-gatherers frequently visit. Soon they start trading, and a few foragers learn how to cultivate plants. Over time, more people see the benefits of a stable crop supply and switch from hunting to farming.
Likewise, picture groups of farmers clearing woods to create spaces for husbandry and agriculture. In doing so, they can (even inadvertently) ruin hunting spots during the process, forcing the hunter-gatherers to move elsewhere.
These scenarios might seem obvious, but considering them pushes us to look for more nuanced explanations further than environmental drivers. While such drivers can play a role, our findings suggest that the demographic makeup, how many farmers there are compared to foragers, and how likely foragers are to jump ship, can be crucial in the spread of farming.
The same dynamics might explain other moments in human history where two groups interacted. For instance, sometimes early humans migrating into Neanderthal territory mixed with the local populations .
On the other hand, the spread of horse-riding groups over Eurasia from 3000BC provoked a major demographic turnover . People adapt to their ever-changing contexts, which causes a snowball effect.
Perhaps the biggest takeaway is that human connectivity is key for cultural and technological change. Our approach isn't meant to exclude other explanations like climate fluctuations . But it does remind us to think about how simple social exchanges; marriages, friendships or alliances, as well as conflicts, can shape communities.
Today we think nothing of adopting a new app or gadget once enough people around us use it, in the same way that we often stick to our good ol' way of doing things, despite being aware of better alternatives.
Ancient groups might have shown similar patterns on a massive scale during the spread of farming. Seeing these parallels helps us understand how humans behave in groups, whether in a prehistoric village, or a modern metropolis.
Alfredo Cortell receives funding from the European Commission: MSCA-IF ArchBiMod project H-2020-MSCA-IF-2020 actions (Grant No. 101020631) and The Humboldt Foundation (Grant ID: 1235670). This work has received funding from the following projects: ERC-StG project ENCOUNTER (Grant No. 801953); Synergy Grant project COREX: From Correlations to Explanations: towards a new European Prehistory (Grant Agreement No. 95138). The projects PID2021-127731NB-C21 EVOLMED "Evolutionary cultural patterns in the contexts of the neolithization process in the Western Mediterranean," MCIN/AI/10.13039/ 501100011033 ERDF A way of making Europe are funded by the Spanish Government, and Prometeo/2021/007 NeoNetS "A Social Network Approach to Understanding the Evolutionary Dynamics of Neolithic Societies (C. 7600-4000 cal. BP)" is funded by the Generalitat Valenciana. Open access funding has been provided by the Max Planck Society.
Javier Rivas does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
