Humans really do rule the world. We took over fast and far, more than any other wild vertebrates. We inhabit nearly every corner of the world, and can thrive in deserts, tropical rainforests and even extremely cold climates.
But how?
Scientists say we did it through not only biological evolution, but another system, cultural evolution. And that is what makes us so special.
New research from Arizona State University evolutionary anthropologist Charles Perreault measures just how important culture was relative to biology. He used empirical data to show human global dominance was predominately achieved through cultural evolution.
“As humans moved into new environments, they didn’t have to wait for genetic mutations to adapt to Arctic cold, tropical forests, deserts or high altitudes,” said Perreault, a research scientist at the Institute of Human Origins and an associate professor at ASU’s School of Human Evolution and Social Change.
“Instead, humans adapted through culturally transmitted technologies, ecological knowledge and cooperative social norms. Innovations in clothing, shelter, hunting strategies, food processing and social organization could spread rapidly through social learning.”
The result, his research shows, is that humans encompass about 51 million square miles of land while the typical wild mammal species occupies about 64 square miles.
Perreault’s work demonstrates that if humans were an average mammal that relied only on genetic evolution, achieving today’s geographic range would have required tens of millions of years, thousands of separate species and enormous differences in body size.
“This research helps put human uniqueness into a measurable evolutionary perspective,” Perreault said. “We often say that culture makes us different, but here we can estimate by how much. The results suggest that cultural evolution compressed what would normally require roughly 88 million years of biological diversification into about 300,000 years within a single species.”
“It reframes recent human history as a kind of adaptive radiation — but one powered by cultural diversification rather than speciation — and shows that adding a cultural inheritance system changes how quickly and extensively a lineage can expand.”
To quantify this, Perreault compiled geographic range maps for nearly 6,000 species of terrestrial mammals and aggregated them into genera, families and orders. Then he compared the size and ecological diversity of those ranges to the global human range.
Next, he modeled how range size relates to three indicators of evolutionary change: lineage age, number of species and body-mass variation. Those relationships allow us to estimate how much biological diversification a mammalian clade would typically need to achieve a range as large as ours.
Finally, he compared mammal species’ ranges to cultural group territories to test whether cultural evolution allows humans to specialize at finer spatial scales, showing that culture enables humans to be globally generalist as a species while locally specialized as cultural groups.
“This study is part of a broader effort to build a quantitative science of human macroevolution,” he said. “By combining large comparative datasets with evolutionary theory, we can begin to measure the distinctive role of culture in shaping our species’ trajectory in a way that would have been almost impossible before.”
The article, “Cultural evolution accelerated human range expansion by more than two orders of magnitude,” was published in the journal the Proceedings of the National Academy of Sciences.