People are actively changing landscapes around the world, but shaping ecosystems is not just a modern activity – our ancestors began the transformation nearly 100,000 years ago.
Analysis of human settlements and paleo-ecological data on the northern shores of Lake Malawi in East Africa reveals that the ancients used fire 92,000 years ago to prevent reforestation.
These Stone Age people burned the surrounding forests to make way for a growing population, which led to a sprawling shrub that stretches across the region today.
The study, led by Yale, uncovered settlements in the area, built 92,000 years ago, along with a surge of coal in the lake̵
Analysis of settlements (pictured) and paleoecological data on the northern shores of Lake Malawi in East Africa reveal that ancient inhabitants used fire 92,000 years ago to prevent reforestation
Jessica Thompson, an assistant professor of anthropology at the Faculty of Arts and Sciences and lead author of the article, said: “This is the earliest evidence I’ve seen that humans are radically transforming their ecosystem with fire.
“This suggests that during the late Pleistocene, people learned to use fire in truly new ways. In this case, burning them has replaced the forests in the region with the open forests you see today. ‘
The work began in 2018, when paleoecologists from Pennsylvania State University studied fossils, pollen and minerals in two sedimentary cores pulled from the bottom of Lake Malawi, Scientific America reports.
The analysis showed large ecological turnovers and changes in the environment, which cannot be explained only by climate variables.
The work began in 2018, when paleoecologists from Pennsylvania State University studied fossils, pollen and minerals in two sediment cores (purple, center and right image) extracted from the bottom of Lake Mala. CHA, SS, WW, MGD are locations of ancient settlements
The team found that the lake’s water level and vegetation have had a constant climate pattern for the past 636,000 years, and the shores lining the shore have disappeared during the drought and recovered when the lake reaches normal levels.
However, pollen records show a violation of the cycle about 86,000 years ago.
Researchers have found that when wetter periods return to the region, water levels stabilize, but coastal forests do not recover.
The data also reveal that a jump in coal accumulation occurred shortly before the region’s species richness equalized.
Pollen records show a violation of the cycle about 86,000 years ago. Researchers have found that when wetter periods return to the region, water levels stabilize, but coastal forests do not recover. There was also a jump in coal deposits at the same time as when the ancients first moved to the region.
Despite persistently high lake levels, which suggest greater ecosystem stability, species richness has collapsed since the last dry season based on information from fossilized pollen taken from the lake, the study found.
This was unexpected, as in previous climate cycles, the rainy environment has created forests that provide a rich habitat for an abundance of species, Ivory explained.
Sarah Ivory of Penn said, “The pollen we’re seeing in this most recent period of stable climate is very different than before.”
The population around the lake had to get dressed and the forests were burned to make room for more homes, which led to a sprawling shrub that stretches across the region today.
“In particular, trees that show dense, structurally complex forest canopies are no longer common and are being replaced by pollen from plants that cope well with frequent fires and disturbances.”
Thompson and Ivory worked around Lake Malawi at the same time, so their work intertwined during the excavations.
Thompson discovered ancient settlements surrounding the river that produced tens of thousands of stone relics that helped her and her colleagues date the habitats about 92,000 years ago.
And many of the tools found at the site were used to hunt and cut animal flesh.
Combining their separate discoveries, Ivory and Thompson concluded that the people around the lake must have had dresses and the forests were burned to make room for more homes.
But the team suggested another hypothesis of a coal explosion, including uncontrolled fires in the area or people burning wood to cook food or keep warm.
It’s not clear why people are burning the landscape, Thompson said.
It is possible for them to experiment with controlled burns to create mosaic habitats conducive to hunting and gathering, a behavior documented among hunter-gatherers.
It is possible that their fires burned out of control or that many people simply burned fuel in their environment, which provided heat, cooking or socialization, she explained.
“One way or another, it’s caused by human activity,” she said. “This shows that the early people, for a long time, took control of their environment instead of being controlled by it. They have changed entire landscapes and for better or worse the relationship with our environment continues today. “