In a groundbreaking study examining one of the most influential theories of cultural evolution and geographic determinism, a team of ecologists and cultural evolutionists from the United States, Germany, and New Zealand has undertaken an extensive examination of Jared Diamond’s hypothesis on the axis of orientation. The findings have been published in the journal Evolutionary Human Sciences.
Their research, drawing upon a vast array of cultural, environmental, and linguistic databases, challenges the notion that Eurasia’s geographic layout inherently facilitated a quicker spread of critical innovations compared to other regions of the world, such as the Americas and Africa.
Jared Diamond, in his Pulitzer Prize-winning book Guns, Germs, and Steel, proposed that the differing fates of societies across the globe could largely be attributed to geographical luck. According to Diamond, the east-west axis of Eurasia provided a unique advantage for the spread of agriculture, technology, and innovations due to its relatively uniform climates and day lengths over vast distances.
This contrasted sharply with the predominantly north-south orientation of the Americas and Africa, where varying climates and ecological zones posed significant barriers to the spread of crops and domesticated animals. Diamond argued that these geographical and ecological factors played a crucial role in shaping the disparate rates of societal development and eventual dominance of Eurasian civilizations.
“I read Guns, Germs, and Steel and I was really impressed by its scope,” said first author Angela M. Chira, a postdoctoral researcher at the Max Planck for Evolutionary Anthropology, Department of Linguistic and Cultural Evolution. “Having a background in macroevolution (i.e., working with big questions), I realized I could devise a quantitative test for Diamond’s observations and intuitions. Biogeographic big claims about human history are always impressive and attract a lot of attention, but it is important that we also follow up with big data analyses where that is possible.”
To test Diamond’s hypothesis, the researchers utilized a vast array of data from cultural, environmental, and linguistic databases. The methodology centered around analyzing the relationship between environmental factors — specifically temperature, aridity, and topography — and the transmission of cultural traits among 1,094 traditional societies. This approach allowed the team to assess the ease or difficulty of cultural transmission across different environmental landscapes.
“Our first challenge was to translate what Diamond envisioned into numbers,” Chira explained. “We used least-cost path algorithms to find the paths that minimized differences in temperature and aridity regimes between societies. The length and cost of these paths give us the magnitude of ecological barriers to cultural transmission between two societies, precisely as Diamond envisioned them.”
In line with Diamond’s hypothesis, the researchers found that environmental barriers do indeed impact the likelihood of cultural traits being shared between societies. For example, traits related to subsistence strategies, housing types, and social organization showed significant correlations with environmental and travel barriers, indicating that the ease of cultural transmission for these aspects is closely tied to ecological factors.
However, the researchers discovered that these environmental barriers do not consistently favor Eurasia over other continents. This finding directly challenges Diamond’s assertion that Eurasia’s geographic orientation provided a unique advantage in the spread of agricultural and other critical innovations.
Instead, the study indicates that the facilitation of cultural spread by geographical and ecological conditions is a global phenomenon, with no clear bias towards Eurasia. This suggests that while environmental factors do play a role in shaping the transmission of culture, they do not do so in a way that inherently advantages any one continent’s societies over another’s.
“Big claims are important, but they are often the start of the conversation, and not its conclusion,” Chira told PsyPost. “Our analyses support the hypothesis that yes, environment likely influences how cultural innovations spread, just like Diamond intuited. However, we did not find evidence that the continents’ dominant axis uniformly dictates the potential for cultural spread.”
The study underscores the complexity of cultural transmission, revealing that the spread of innovations is influenced by a myriad of factors beyond environmental and geographic barriers. The findings suggest that factors such as the movement of peoples, direct and indirect cultural exchanges, and perhaps even historical contingencies, play significant roles in shaping the distribution of cultural traits.
Co-author Russell Gray from the Max Planck Institute for Evolutionary Anthropology summarized the results by saying, “Our findings point out that geography, like genetics and ecology, matters, but it is not destiny.”
Looking forward, the study opens up new avenues for research, emphasizing the importance of integrating diverse factors—ranging from ecological to social and historical—in understanding the mechanisms of cultural spread. By challenging the axis of orientation hypothesis, the research invites a reevaluation of how we conceptualize the forces shaping human societies, suggesting that geography is but one of many factors influencing the trajectory of human development.
“Our study offers one quantitative realization of Diamond’s arguments and not a definitive answer,” Chira explained. “I hope it invites people to think harder and deeper on certain matters. The questions Diamond is asking are after all very broad in scope, and need to be decomposed in many smaller and manageable hypotheses. I hope to see others follow-up. I see this study as falling under the general umbrella of work that leverages big open-source datasets to shed light on big questions regarding our history.”
Similarly, senior author of the study, Carlos Botero from the University of Texas at Austin, concluded: “We do not claim, by any means, to have a definitive answer on whether the wheels of history turned at different speeds in different parts of the world. What we aim instead is to provide a new perspective based on quantitative data and thorough analyses, and a blueprint on how the tools and data we already have can be leveraged to test compelling ideas that have strongly shaped the public’s understanding of our own past.”
The study, “Geography is not destiny: A quantitative test of Diamond’s axis of orientation hypothesis,” was authored by Angela M. Chira, Russell D. Gray, and Carlos A. Botero.
