Early Humans Returned to the Rainforests Far Earlier Than Previously Thought

Modern humans evolved around 300,000 years ago, but only began inhabiting rainforests much later. In fact, the earliest archaeological evidence of humans living in rainforest habitats is only about 70,000 years old. Surprising new research suggests that the timeline extends more than 80,000 years further into the past.

After reinvestigating a site in modern-day Côte d’Ivoire, an international team of researchers claims that humans (Homo sapiens) began living in rainforests as early as 150,000 years ago—tens of thousands of years earlier than scholars had previously posited. As detailed in a study published today in the journal Nature, the research confirms the idea that a variety of different landscapes influenced human evolution, and not just open savannas and grasslands.

“Before our study, the oldest secure evidence for habitation in African rainforests was around 18 thousand years ago and the oldest evidence of rainforest habitation anywhere came from southeast Asia at about 70 thousand years ago,” Eslem Ben Arous, an archaeologist at the Max Planck Institute of Geoanthropology and lead author of the study, said in a statement. “This pushes back the oldest known evidence of humans in rainforests by more than double the previously known estimate.”

Yodé Guédé, a co-author on the study from the Université Félix Houphouët-Boigny, first studied the location in question in the 1980s. Guédé and colleagues discovered a stratified site with stone tools in a Côte d’Ivoire rainforest, but were unable to determine the age of the tools.

“With Professor Guédé’s help, we relocated the original trench and were able to re-investigate it using state of the art methods that were not available thirty to forty years ago,” explained James Blinkhorn, an archaeologist at the University of Liverpool who participated in the study. The team determined the site to be 150,000 years old. They also analyzed the presence of plant remains within sediment samples to confirm that the region had been a rainforest all those years ago.

“Convergent evidence shows beyond doubt that ecological diversity sits at the heart of our species,” said Eleanor Scerri, an archaeologist at the Max Planck Institute of Geoanthropology and study senior author. “This reflects a complex history of [Homo sapiens] population subdivision, in which different populations lived in different regions and habitat types,” she added. “We now need to ask how these early human niche expansions impacted the plants and animals that shared the same niche-space with humans. In other words, how far back does human alteration of pristine natural habitats go?”

According to savanna hypothesis of human evolution, our ancient human ancestors’s transition from forested habitats to open landscapes millions of years ago favored the development of crucial features and behaviors such bipedalism, the use of tools, and hunting strategies. The study ultimately challenges the tendency to overlook the role of rainforests in the consequent development of modern humans, and questions what, if any, further evolution occurred as a result of some members of our species choosing to live among trees again. And to Scerri’s point, this raises important questions about the potential ways in which our species altered these rainforests upon their return.

Ultimately, the study rewrites the history of prehistoric human habitats, and paves the way for studying the long-overlooked role of rainforests in the development of modern humans.