Humans May Have Lived in Tropical Rainforests Much Earlier Than Scientists Previously Thought, Study Finds

Scientists have found that early humans lived in tropical rainforests much earlier than previously thought, a discovery that sheds new light on Homo sapiens’ ability to adapt to different environments.

The rainforests of West Africa were home to humans roughly 150,000 years ago, according to a recent study published in the journal Nature. These findings suggest that our ancestors may have evolved in several different regions on the continent and were able to survive in a wide variety of ecosystems.

Previously, the earliest known evidence of humans living in rainforests dated to roughly 70,000 years ago in southeast Asia. In Africa, the earliest evidence of human rainforest habitation dated to 18,000 years ago.

“Our results push back the earliest known presence of humans in tropical forests by more than twice the previously established estimate in another region of the world and also in Africa,” says co-author Eslem Ben Arous, an archaeologist at the Max Planck Institute of Geoanthropology in Germany, to Live Science’s Jess Thomson.

The findings add to the growing body of evidence that Homo sapiens may have originated from multiple locations throughout Africa roughly 300,000 years ago, rather than just one place on the continent. 

They also challenge the long-held assumption that humans first evolved in open grasslands and only later learned how to live in other, more challenging ecosystems like rainforests.

“It reinforces the idea that humans have multiple roots across Africa, and that from our inception almost we were a species that could and did survive in very, very different ecosystems,” co-author Eleanor Scerri, also an archaeologist at the Max Planck Institute of Geoanthropology, tells USA Today’s N’dea Yancey-Bragg. “And the same skills that allowed us to do that are the same skills that have put us on the moon and have us looking forward to going to Mars.”

Researchers reached these conclusions after reinvestigating an archaeological site in Anyama, a city in Ivory Coast. The site, called Bété I, was originally excavated in the 1980s. However, the researchers were unable to date the artifacts they’d unearthed, including stone tools.

Recently, scientists revisited Bété I and completed a new round of excavations, which turned up more stone tools. They also used modern techniques to investigate the artifacts and the site’s sediment layers. These methods suggest the stone tools date back at least 150,000 years.

In addition, the team analyzed the remnants of plants that had been preserved at the site. These experiments indicate the region was a humid, heavily wooded forest 150,000 years ago, full of dense shrubs and large trees like African elemi (Canarium schweinfurthii) and African oil palm (Elaeis guineensis).

“It is genuinely tropical forest,” says Ceri Shipton, an archaeologist at University College London who was not involved with the research, to New Scientist’s Michael Marshall. “And I think the dating is pretty convincing as well.”

The stone tools themselves offered even more support for the idea that early humans were living in the tropical rainforest. Made from quartz, they appear to have been chopping tools that humans may have used to dig up food or cut back plants as they moved through the dense landscape.

The researchers say 150,000 years may be an underestimate. The specialized tools suggest humans were already accustomed to living in the rainforest by that point.

“They’re not people who have just arrived,” Scerri tells the New York Times’ Carl Zimmer. “These are people who had the time to adjust to their living conditions.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.