A mathematical formula has been developed that accurately charts the rise of complex societies through 3000 years of history, with access to warhorses one of the crucial inputs.
The study highlights the significant part horses played in the rise of mankind’s great civilisations.
The question of how human societies evolved from small groups to the huge, anonymous and complex societies of today was answered by the scientists mathematically, whose formula accurately matched the historical record on the emergence of complex states in the ancient world.
Intense warfare was the evolutionary driver of large complex societies, the researchers found – and to make war effectively, they needed horses.
The study, published this week in an open-access article in the journal, Proceedings of the National Academy of Sciences, was carried out by researchers from the University of Connecticut, the University of Exeter in England, and the National Institute for Mathematical and Biological Synthesis (NIMBioS).
Their model successfully predicted where and when the largest-scale complex societies arose in human history.
Essentially, it helped explain why complex societies developed and spread in some areas but not in others.
Simulated within a realistic landscape of the Afro-Eurasian landmass during 1500 BCE* to 1500 CE, the model was tested against the historical record.
During the time period, horse-related military innovations, such as chariots and cavalry, dominated warfare within Afro-Eurasia.
Geography also mattered, as nomads living in the Eurasian Steppe influenced nearby agrarian societies, thereby spreading intense forms of offensive warfare out from the steppe belt.
The study focused on the interaction of ecology and geography, as well as the spread of military innovations.
It found that selection for ultra-social institutions that allow for cooperation in huge groups of genetically unrelated individuals and large-scale complex states was greater where warfare is more intense.
While existing theories on why there is so much variation in the ability of different human populations to construct viable states are usually formulated verbally, the authors’ work leads to sharply defined quantitative predictions, which can be tested against history.
The model-predicted spread of large-scale societies was very similar to the observed one. The model was able to explain two-thirds of the variation in determining the rise of large-scale societies.
“What’s so exciting about this area of research is that instead of just telling stories or describing what occurred, we can now explain general historical patterns with quantitative accuracy,” said the study’s co-author, Sergey Gavrilets, who is the NIMBioS director for scientific activities.
“Explaining historical events helps us better understand the present, and ultimately may help us predict the future.”
In building the model, the scientists divided Africa and Eurasia into gridded squares categorized by environmental variables, such as habitat, elevation, and the presence or otherwise of agricultural activity at 1500 BCE, when the simulation began.
They then inserted military technology as it was then known into the squares around the grasslands of central Asia, where domesticated horses were likely to have first become a dominant force in warfare.
The model allowed for the spread of horse domestication and other influencing factors. It simulated conflict throughout the 3000 years on which the study focused.
The model proved to be mostly correct, showing empires arising in most of the right places, as shown in history.
The scientists acknowledged that many variables that would have played a part in the development of societies had not been factored into the equation, but the research nonetheless showed that there was a lot of quantitative data in history.
Peter Turchina, Thomas E. Currie, Edward A. L. Turner, and Sergey Gavrilets, War, space, and the evolution of Old World complex societies, September 23, 2013, doi: 10.1073/pnas.1308825110
* BCE – Before the Common Era; previously termed as ‘BC’ – Before Christ; but now known as ‘BCE’