A groundbreaking study published in Nature on February 26, 2025, has revealed compelling evidence that humans lived in African rainforests much earlier than previously thought. This discovery challenges long-held assumptions about human adaptation and evolution.
For decades, the prevailing narrative about human evolution has emphasized the importance of savannas and coastal regions as the key environments where our species developed and thrived. But what if our story is more complex? What if we’ve been underestimating our ancestors’ adaptability all along?
A Remarkable Discovery
An international team of researchers led by Eslem Ben Arous, James A. Blinkhorn, and Eleanor M. L. Scerri has uncovered evidence that humans were living in wet tropical forests in what is now Côte d’Ivoire around 150,000 years ago. This finding, published in Nature, pushes back the earliest known clear association between humans and rainforest habitats by more than 130,000 years.
The evidence comes from a site called Bété I, located near Anyama in southern Côte d’Ivoire. Here, researchers found stone tools and other artifacts embedded in sediments that, through multiple dating methods and environmental analyses, clearly indicate a wet tropical forest environment dating to approximately 150,000 years ago—during what geologists call Marine Isotope Stage 6 (MIS 6).
Why This Matters
This discovery is significant for several reasons. First, it challenges the long-standing belief that dense rainforests were barriers to human habitation until much more recently in our evolutionary history. The conventional wisdom has been that humans primarily evolved in open grasslands and only later developed the technologies and adaptations necessary to survive in more challenging environments like rainforests.
Second, it provides important evidence for what scientists call the “pan-African” model of human evolution—the idea that our species emerged through interconnected populations across multiple African environments, not just in a single region.
“The assemblage in Unit D, featuring large tools alongside a small tool component, may support long-held views that the diverse heavy-duty tool assemblages seen in Central and West Africa are convergent adaptive solutions to tropical forest habitation,” the researchers note in their paper.
The Science Behind the Discovery
The team employed an impressive array of scientific techniques to reach their conclusions. They used optically stimulated luminescence (OSL) and electron spin resonance (ESR) dating methods to determine the age of the sediments containing the artifacts. These methods measure when mineral grains were last exposed to light or heat, effectively creating a timestamp for when they were buried.
Just as important were the environmental analyses. The researchers examined plant waxes, stable isotopes, phytoliths (microscopic silica structures formed in plants), and pollen preserved in the sediments. All these indicators consistently pointed to a wet forest environment—not an open savanna or woodland.
The phytolith assemblages showed 82-96% tree/shrub representation, with minimal grass presence. Pollen analysis revealed species typical of wet tropical forests, including oil palm and plants associated with riparian (riverside) habitats. Even the chemical signatures from plant waxes indicated a predominance of forest vegetation.
Changing Our Understanding of Human Capabilities
This discovery suggests that early humans were far more adaptable than we’ve given them credit for. Living in a dense tropical forest requires different skill sets and technologies than surviving on open grasslands. Forests offer different food resources, challenges for movement and navigation, and unique threats from predators and diseases.
The stone tool assemblages found at Bété I include both large tools—such as picks and choppers—and smaller, more refined implements. This combination might represent specialized adaptations for forest living, potentially for activities like processing fibrous plants, working with wood, or harvesting and processing forest foods.
It’s worth noting that the tools found in the oldest layers (Unit D) don’t fit neatly into established archaeological classifications for African stone tools. This suggests either regional variation in tool-making traditions or specialized adaptations to forest environments that archaeologists haven’t fully characterized yet.
A Broader Context: Human Adaptability
This study adds to growing evidence that our species has been remarkably adaptable throughout its history. Recent research has shown early humans living in high-altitude environments, arid deserts, and even the Arctic much earlier than previously believed.
The ability to adapt to diverse environments may have been one of the defining characteristics that allowed Homo sapiens to eventually spread across the entire planet. This adaptability likely involved both technological innovation and social cooperation—hallmarks of our species that continue to define us today.
Looking Forward
The Bété I site was unfortunately destroyed by quarrying activities between 2020 and 2021, highlighting the urgent need for archaeological conservation efforts worldwide. However, the data collected before its destruction will continue to inform our understanding of human evolution and adaptation.
This discovery opens new avenues for research. If humans were living in rainforests 150,000 years ago, what other environments might they have conquered even earlier? How did they develop the technologies and social strategies to thrive in such challenging settings? And how might this change our understanding of human cognitive development?
As our tools for analyzing ancient environments and dating archaeological sites continue to improve, we may find that the story of human evolution is even more fascinating—and more complex—than we’ve imagined.
The findings from Bété I remind us that our ancestors were innovative problem-solvers, capable of adapting to diverse challenges—a trait that continues to define humanity today.
Editor’s note: This article provides analysis and commentary on research published in Nature. For the original research paper, please refer to: Ben Arous, E., Blinkhorn, J.A., Elliott, S. et al. “Humans in Africa’s wet tropical forests 150 thousand years ago.” Nature (2025). Link.
