Ecosystem Engineers: Oldest Evidence to Date of Humans Changing Entire Ecosystems with Fire

It's no question that for better or for worse, humans have actively take a role in shaping the ecosystems they've been a part of - and a new study might've found the oldest evidence to date.

The dominance of mankind over the natural world most likely began when it first mastered how to use fire, with a new archaeological discovery of stone artifacts dated back to as old as 92,000 years ago. Combined with paleoenvironmental data taken from the northern shores of Lake Malawi, in East Africa, it found evidence that man actually used fire to become ecosystem engineers. Evidence points to humans using fire in a way that prevented the regrowth of forests in the area, which led to the development of bushland that remains until today.

Researchers present their study in the article "Early human impacts and ecosystem reorganization in southern-central Africa," appearing in the journal Science Advances.

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An International Effort Between Researchers

In a video available in the YaleCampus YouTube Channel, study author and paleoanthropologist Jessica Thompson from Yale University describes the earliest evidence that suggests mankind used fire to actively shape their ecosystems.

"This is the earliest evidence I have seen of humans fundamentally transforming their ecosystem with fire," Thompson said. She then explains that by the Late Pleistocene period, humans were starting to find more uses for fire. In the case documented in their study, mankind used fire to change their ecosystems, converting a part of the forest into large woodlands she features in the video.

Thompson led the study with 27 other colleagues in an international collaboration, including members from the US, Africa, Asia, Europe, and Australia. Together with the Malawi Department of Museums and Monuments, Thompson and David Wright from the University of Oslo led efforts to date the archaeological sites with Penn State's Sarah Ivory leading the paleoenvironmental analysis for the study.

The combined effort led to the analysis of artifacts believed to be from the Middle Stone Age - a period that dates back at least 315,000 years. It was marked by the appearance of the first modern humans, backed by progress in the species' cognition and social behavior.

Humans as Ecosystem Engineers

Thompson and Wright put in a number of field seasons doing archaeological work in the area before a meeting with Ivory helped them better understand the patterns they earlier found in their data. Specifically, the Lake Malawi archaeological record shows that its ecological changes and the formation of alluvial fans - fan-shaped deposits of silt and stone at locations where the rate of water flow changed - are most probably connected events.

While Lake Malawi has seen its water levels drastically change over the ages, one of its driest periods occurred some 85,000 years ago. During this instance, it shrunk down into two smaller, saltier forms of water. Since then, Lake Malawi has recovered and water levels remained relatively high ever since.

Researchers then discovered that a spike in the accumulation of charcoal materials happened shortly before the species richness - the variety of species living in it - started to decline. Although the lake levels remained consistently high, the species richness did not - an unusual behavior considering other environmental factors considered in the region.

They then explain that the burning in the region, paired with climate-driven changes, created conditions that allowed for the preservation of artifacts in the region. While it remains unknown exactly why people burned the landscape, it was possible that they were still experimenting on how to control fire. Either way, this shows mankind as ecosystem engineers, whose actions changed the ecosystems they live in.