Rainforests are a major world biome which humans are not thought to have inhabited until relatively recently. New evidence now shows that humans lived in west Africa’s rainforests by at least 150 thousand years ago.
Humans originated in Africa around 300 thousand years ago, but the ecological and environmental contexts of human evolution are still little understood. In the search for answers, rainforests have often been overlooked and generally thought of as natural barriers to human habitation.
Now, in a new study published in Nature, an international team of researchers, including Dr. Chris Kiahtipes, an environmental archaeologist and USF Libraries’ Florida Environment and Natural History (FLENH) special collections curator, challenge this view with the discovery that humans were living in rainforests within the present-day Côte d’Ivoire much earlier than previously thought. The article reveals that human groups were living in rainforests by 150 thousand years ago and argues that human evolution occurred across a variety of regions and habitats.
“Before our study, the oldest secure evidence for habitation in African rainforests was around thousand years ago and the oldest evidence of rainforest habitation anywhere came from southeast Asia at about 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.”
In addition to dating techniques, sediment samples from the Côte d’Ivoire site 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.
“What does it take to prove that people were in the forest 150,000 years ago?” Kiahtipes asks. “You need artifacts, some way of assigning the deposits to a specific time, and chemical and physical evidence that this location was a forest. My part of the project was identifying plant fossils (pollen) that indicated that this was indeed a rainforest.”
“The geochemistry showed evidence for this being a forested riparian zone, and the pollen show remarkable agreement. Even better, we found fragments of anthers (the part of a stamen that contains pollen), which is a strong indicator that the vegetation types were local. I found oil palm and some other distinctive wet rainforest plants,” says Kiahtipes.
Kiahtipes’ work on this exciting discovery is as part of an international team of researchers funded by the Max Planck Society and the Leakey Foundation. This research not only changes our understanding of how and where humans evolved but also has present-day scientific, cultural, and social impacts.
Kiahtipes notes that “the significance of this study is that our team documented the earliest human habitation of the tropical rainforest zone, ever. There are long-standing debates about when people started living in rainforest environments and a history of assuming that rainforests are ‘natural’ environments (i.e. without people), while savannas are ‘cultural’ environments. This has huge conservation and humanitarian implications, as there are still thousands of hunter-gatherers and rural villages living in tropical forest environments whom are often the targets of abuse and removal because of these assumptions.”
Kiahtipes’ work connects how we use natural history collections, such as the USF Herbarium, to create reference material. “Collections are an essential part of this research. When we’re looking at these tiny plant pieces that preserve in sediments, we need a reference from a known plant to make an identification. These are only available from research collections like the USF Herbarium.”
Overall, Kiahtipes points out, “This paper published in Nature tells a story about how important forested waterways are, which is something that you see over and over in the USF Libraries’ FLENH collections–these are globally critical environments for people, past and present.”
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Publication Information Title: Humans in Africa’s wet tropical forests 150 thousand years ago
Authors: Eslem Ben Arous, James A. Blinkhorn, Sarah Elliott, Christopher Kiahtipes, Charles D. N’zi, Mark D. Bateman, Mathieu Duval, Patrick Roberts, Robert Patalano, Alexander 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 Scerri
Publication: Nature
DOI: 10.1038/s41586-025-08613-y