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Did a changing climate lead to increased conflict among the city-states of the famous Classic Maya civilization (ca. 250-900 CE)? According to some researchers, a decline in rainfall exacerbated conflict for the Classic Maya. However, other researchers have found that increasing summer temperatures influenced Classic Maya conflict levels. A recent study from a team led by Simon Fraser University (SFU) Professor of Archaeology and Canada Research Chair in Human Evolutionary Studies Mark Collard provides a new perspective on this debate.

An enthusiastic proponent of interdisciplinary research, Collard’s work brings together conceptual and analytical tools from various fields to test hypotheses about human evolution and social change. In his study, Rainfall, temperature, and Classic Maya conflict: A comparison of hypotheses using Bayesian time-series analysis, he collaborated with SFU alumnus Chris Carleton, who currently works at the Max Planck Institute for Chemical Ecology in Jena, and former SFU Professor Dave Campbell, who is now based at Carleton University in Ottawa.

The study compared known rainfall and temperature data from the Classic Period with records of conflicts that were kept by the Maya. Collard and his colleagues found that increasing summer heat exacerbated conflict, while annual rainfall variation did not. These findings add not only to the understanding of conflict in the Maya region at the time, but also have important implications for the understanding of contemporary climate change.

We talked with Mark Collard about his research.

Your study found that increased summer temperature did contribute to conflict for the Classic Maya. Other studies suggest different reasons, such as rainfall fluctuation, or colder weather precipitated conflict. How do you explain these different research findings?

When we refer to the differences in the results of studies that have focused on Classic Maya conflict, I think the key issue is that previous authors have either not formally tested the predictions of the climate change hypothesis or not included both of the key variables, i.e. rainfall and temperature. On the other hand, when talking about the differences in the results of studies that have looked at climate change and conflict in different regions of the world, I suspect this is because the impact is mediated by local factors such as latitude, the nature of the available food resources and the cultural history of the region. For example, Chris, Dave and I think that our Classic Maya results are dependent on the Classic Maya’s reliance on maize and the options their elite class had for staying in power, which seem to have been to ensure a good maize harvest or win battles. This combination will not be found in many other places, so it is quite likely that other regions will not return results that are similar to our Classic Maya results. Consistent with this, in another recent study we examined the impact of climate change on conflict in Europe, where the main resources and cultural history are quite different, and did not find any effect.

You observed that the Maya adapted their agriculture to respond to variations in rainfall–for example, they intensified terracing of the fields, engaged in hydro engineering projects and used reservoirs. Still, you found that increased summer heat was detrimental to the maize harvest. Does your research point to ways that modern society can cope with climate change?

I do not think our work points to a particular practical way in which modern society can cope with climate change. Instead, I think the relevance of our work for contemporary climate change is to highlight that the impacts are likely to be different in different parts of the world, and that means we should avoid black-and-white, one-size-fits-all thinking. Some regions may be quite badly affected by climate change-induced conflict while others may not be affected at all. And it’s unlikely to be simply an effect of geography; sociocultural differences that have arisen over hundreds, if not thousands, of years are also likely to be important. The situation is almost certainly going to be complex. The corollary of this for me is that we should try to approach the debate about the effects of climate change, and how we reduce those effects, with humility and tolerance of alternative points of view. We have not done a very good job of listening to each other during COVID, so I’m not hugely optimistic that we’ll be able to do so in relation to climate change. But I really think we should try.

Much of your research involves testing theories and concepts with mathematical and statistical analysis. How did you first embark on this type of work? Is it challenging to find the necessary records and documentation to test your hypotheses?

I discovered Darwinian theory and the power of the scientific method as a second-year undergraduate student in the Department of Archaeology and Prehistory at the University of Sheffield in the early 1990s and I’ve been using them to try to understand the human story ever since. Prior to becoming a fan of Darwin’s theory, I was obsessed with trying to use Marxism to do archaeological research. That obsession did not survive a course in Landscape Archaeology taught by Professor Andrew Fleming, however. Much to my horror, Andrew called my Marxism-infused project report ‘pretentious twaddle.’ Once my bruised ego had healed, I realized he was right and decided to look for a better framework. Darwinian theory was the alternative I settled on and the professors in the department encouraged me to run with it even though they were very skeptical about it as a way to approach archaeology. Interestingly, the discipline has changed a lot since then and evolutionary approaches are now accepted as normal in archaeology. As far as the data side of things is concerned, I have not really had a problem locating datasets to work with. There is a huge amount of data lying dormant in the literature and, if a suitable dataset is not available in the literature, there are lots of museum collections to work with.

To learn more about Mark Collard’s research visit: