According to a recent report, humans living along the northern shores of East Africa’s Lake Malawi were altering the local landscape with fire as early as 92,000 years ago.
Analysis of stone artifacts and paleoenvironmental data — detailed Wednesday in the journal Science Advances — suggests fire use by early humans prevented regrowth of the region’s forests, yielding the expansive bushland that persists today.
“This is the earliest evidence I have seen of humans fundamentally transforming their ecosystem with fire,” lead author Jessica Thompson said in a press release.
“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,” said Thompson, an assistant professor anthropology at Yale University.
Scientists were able to determine the effects of human activity on local environments by studying stone tools and sediment cores obtained from excavation sites along the lake’s alluvial fan, as well as from the lake’s bottom.
Observations in the field showed many distinct trends, including changes in sedimentation and charcoal deposition about 92,000 years ago.
Pollen signatures showed a flattening of the region’s species diversity shortly after the first increase in charcoal accumulation, according to the researchers.
“The pollen that we see in this most recent period of stable climate is very different than before,” said co-author Sarah Ivory, assistant professor of geosciences at Penn State.
“Specifically, trees that indicate dense, structurally complex forest canopies are no longer common and are replaced by pollen from plants that deal well with frequent fire and disturbance,” Ivory said.
According to the researchers, what seemed to be discrete archaeological and temperature trends began to become intertwined.
Scientists discovered a plethora of archaeological sites at the same time as the region’s forests were dwindling and a huge alluvial fan emerged along Lake Malawi’s northern shores.
The use of fire by early human populations in the area not only helped change the region’s ecology, but also assured the preservation of thousands of Middle Stone Age artefacts.
“Dirt rolls downhill unless there is something to stop it,” said co-author David Wright, an archaeologist at the University of Oslo. “Take the trees away, and when it rains, there is a lot of dirt moving downhill in this environment.”
Researchers are baffled as to why these early human communities burned so much ground. It’s likely that hunter-gatherers in the area used regulated burns to create open landscapes more favourable to hunting, in addition to burning fuel for heating and cooking.
What is certain is that these were not forest fires.
“One way or another, it’s caused by human activity,” Thompson said. “It shows early people, over a long period of time, took control over their environment rather than being controlled by it. They changed entire landscapes, and for better or for worse that relationship with our environments continues today.”