Beginning in roughly 10,000 B.C., people around the world adopted large-scale farming as part of the Neolithic Revolution. But humans in need of resources have been shaping their surroundings for much, much longer than that. As a new study published in the journal Science Advances suggests, Stone Age people in southeastern Africa used fire to intentionally transform the landscape around Lake Malawi some 85,000 years ago.
“This is the earliest evidence I have seen of humans fundamentally transforming their ecosystem with fire,” says lead author Jessica Thompson, a paleoanthropologist at Yale University, in a statement. “It suggests that by the Late Pleistocene, humans were learning to use fire in truly novel ways. In this case, their burning caused replacement of the region’s forests with the open woodlands you see today.”
Per Katarina Zimmer of Scientific American, clues to the landscape’s transformation came from fossils, pollen and minerals uncovered by co-author Sarah Ivory, a paleoecologist at Pennsylvania State University. Ivory’s team found that the lake’s water level and nearby vegetation experienced a repeated climatic pattern over a period of 636,000 years. Forests along the shore disappeared during dry stretches and returned as the lake refilled.
That changed about 86,000 years ago, when the lake’s water levels rose but the forests only recovered briefly. The woods collapsed, leaving behind fire-tolerant species and allowing grass to spread across the shore area. The researchers speculate that the shift was tied to human settlement in the area, which began around 92,000 years ago.
Writing for the Conversation, Thompson, Ivory and co-author David K. Wright of the University of Oslo describe a sudden spike in charcoal in the area 85,000 years ago. This uptick could be the result of humans’ deliberate use of fire, which people have used for warmth and cooking for at least a million years. Many modern hunter-gatherers employ fire as a tool to improve land’s productivity, noted Gleb Raygorodetsky for Naational Geographic in 2016.
“By converting the natural seasonal rhythm of wildfire into something more controlled, people can encourage specific areas of vegetation to grow at different stages,” the authors explain for the Conversation. “This so-called ‘pyrodiversity’ establishes miniature habitat patches and diversifies opportunities for foraging, kind of like increasing product selection at a supermarket.”
As the land along Lake Malawi shifted from dense, canopied forests to more open woodland with grasses and shrubs, biodiversity dropped. But the change created a more beneficial environment for the region’s human inhabitants.
“We think of fire often as this destructive tool,” says Thompson in a video released by Yale. “That doesn’t have to be the case, because if you have the right kind of ecological knowledge and you know exactly where and when to set the fires and how to control them, what you can actually do is shape the landscape to do your bidding, in a sense.”
The researcher adds, “You can clear out undergrowth strategically, and then you can make new grass come up, and that draws in all the animals that like to hang out in those kinds of habitats.”
Though the burning of the area around Lake Malawi could have been unintentional, perhaps resulting from cooking fires that spread out of control, Patrick Roberts, an archaeologist at the Max Planck Institute for the Science of Human History who was not involved in the new study, tells Scientific American that the connections the study makes between humans and the sudden ecological change is convincing. He says experts have no reason to think that Stone Age people didn’t plan the fires to improve their dining options.
Roberts asks, “Why else would you go and set fire to the landscape?”