When it comes to the origins of our species, Homo sapiens, most scholars have accepted that we originated in Africa around 300,000 years ago, likely from a single population.
However, research published in the journal Trends in Ecology & Evolution has challenged this view, suggesting that our ancestors were scattered across the entire African continent and did not stem from a specific region.
This fractured evolution meant that our species was both physically and culturally diverse right from the very beginning, according to an interdisciplinary group of researchers led by Eleanor Scerri, an archaeologist from the University of Oxford and the Max Planck Institute for the Science of Human History.
For the study, the team combined approaches from various disciplines, including anthropology, archaeology and genetics, in addition to reconstructing Africa’s past climate, to build a picture of how modern humans have evolved over the last 300,000 years.
They found that not only were Homo sapiens scattered across Africa when we emerged as a species, but these populations were also largely kept apart due to a combination of physical barriers, such as forests and deserts, leading to diversification.
However, these environments often shifted over time, spurring migrations which created some contact opportunities. This may have meant that populations could have gone through cycles of cultural and genetic mixing before becoming isolated again.
This new model of human evolution better explains the available genetic, fossil and archaeological evidence, the researchers said.
For example, this model can explain why human bone fossils from the last 300,000 years vary significantly, with a mix of archaic and modern features appearing in different places and at different times.
“In the fossil record, we see a mosaic-like, continental-wide trend toward the modern human form, and the fact that these features appear at different places at different times tells us that these populations were not well connected,” Scerri, said in a statement.
The archaeological evidence also lends weight to the new hypothesis.
“Stone tools and other artifacts—usually referred to as material culture—have remarkably clustered distributions in space and through time,” Scerri said. “While there is a continental-wide trend toward more sophisticated material culture, this ‘modernization’ clearly doesn’t originate in one region or occur at one time period.”
Finally, the team’s analysis of the available genetic data indicates that the single origin model is insufficient, according to Mark Thomas, a geneticist from University College London and co-author of the study.
“It is difficult to reconcile the genetic patterns we see in living Africans, and in the DNA extracted from the bones of Africans who lived over the last 10,000 years, with there being one ancestral human population,” he said. “We see indications of reduced connectivity very deep in the past, some very old genetic lineages, and levels of overall diversity that a single population would struggle to maintain.”
The new research highlights how the evolution of modern humans in Africa was a multiregional, multiethnic and multicultural phenomenon, Scerri concluded.