Lost in the Rainforest for 150,000 Years – The Discovery That Rewrites Human History

For years, rainforests were thought to be barriers to early human survival, but new evidence has shattered this assumption.

A groundbreaking study reveals that humans were thriving in the rainforests of Côte d’Ivoire 150,000 years ago — more than double the previous estimate. This discovery rewrites our understanding of early human adaptability and suggests that our ancestors lived in far more diverse environments than once believed.

Humans in Rainforests: An Ancient Connection

Rainforests are one of the world’s major biomes, but until recently, scientists believed humans only began inhabiting them in the not-so-distant past. However, new evidence now reveals that humans were living in African rainforests at least 150,000 years ago — the earliest known proof of rainforest habitation by our species.

Humans first emerged in Africa around 300,000 years ago, but many details about the environments in which we evolved remain unclear. Rainforests, in particular, have often been overlooked in these discussions, traditionally seen as difficult environments for early human survival.

Groundbreaking Discovery in Côte d’Ivoire

Now, a groundbreaking study published today (February 26) in Nature challenges this assumption. An international team of researchers has discovered that humans were living in the rainforests of present-day Côte d’Ivoire far earlier than previously thought. Their findings suggest that human evolution took place across a much wider range of habitats than once believed, reshaping our understanding of how our ancestors adapted to different environments.

The Origins of the Investigation

The story of this discovery begins in the 1980s, when the site was first investigated by co-author Professor Yodé Guédé of l’Université Félix Houphouët-Boigny on a joint Ivorian-Soviet mission. Results from this initial study revealed a deeply stratified site containing stone tools in an area of present-day rainforest. But the age of the tools – and the ecology of the site when they were deposited there – could not be determined.

“Several recent climate models suggested the area could have been a rainforest refuge in the past as well, even during dry periods of forest fragmentation,” explains Professor Eleanor Scerri, leader of the Human Palaeosystems research group at the Max Planck Institute of Geoanthropology and senior author of the study. “We knew the site presented the best possible chance for us to find out how far back into the past rainforest habitation extended.”

Cutting-Edge Methods Reveal a New Timeline

The Human Palaeosystems team therefore mounted a mission to re-investigate the site. “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,” says Dr. James Blinkhorn, researcher at the University of Liverpool and the Max Planck Institute of Geoanthropology. The renewed study took place just in time, as the site has since been destroyed by mining activity.

“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,” explains Dr. Eslem Ben Arous, researcher at the National Centre for Human Evolution Research (CENIEH), the Max Planck Institute of Geoanthropology and lead author of the study. “This pushes back the oldest known evidence of humans in rainforests by more than double the previously known estimate.”

Scientific Techniques Confirm the Findings

The researchers used several dating techniques, including Optically Stimulated Luminescence and Electron-Spin Resonance, to arrive at a date roughly 150 thousand years ago.

At the same time, sediment samples were separately investigated for pollen, silicified plant remains called phytoliths, and leaf wax isotopes. Analyses indicated the region was heavily wooded, with pollen and leaf waxes typical for humid West African rainforests. Low levels of grass pollen showed that the site wasn’t in a narrow strip of forest, but in a dense woodland.

The Start of More Exciting Discoveries

“This exciting discovery is the first of a long list as there are other Ivorian sites waiting to be investigated to study the human presence associated with rainforest,” says Professor Guédé joyfully.

“Convergent evidence shows beyond doubt that ecological diversity sits at the heart of our species,” says Professor Scerri. “This reflects a complex history of population subdivision, in which different populations lived in different regions and habitat types. 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?”

Reference: “Humans in Africa’s wet tropical forests 150 thousand years ago” by Eslem Ben Arous, James A. Blinkhorn, Sarah Elliott, Christopher A. Kiahtipes, Charles D. N’zi, Mark D. Bateman, Mathieu Duval, Patrick Roberts, Robert Patalano, Alexander F. Blackwood, Khady Niang, Eugénie Affoua Kouamé, Edith Lebato, Emily Hallett, Jacopo N. Cerasoni, Erin Scott, Jana Ilgner, Maria Jesús Alonso Escarza, Francois Yodé Guédé and Eleanor M. L. Scerri, 26 February 2025, Nature.
DOI: 10.1038/s41586-025-08613-y

The research was funded by the Max Planck Society and the Leakey Foundation.

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