Researchers have long known that the discovery of fire was a game-changer for early humans, but exactly how our ancestors came to harness this powerful force has long been the source of heated debate. Now, a University of Utah team believes they’ve found the answer.
In a paper published Sunday by the journal Evolutionary Anthropology, lead author Christopher Parker, a postdoctoral researcher in the university’s anthropology department, and his colleagues presented a new hypothetical scenario which proposes that early humans first became reliant on flame due to Africa’s increasingly fire-prone environment some 2-3 million years ago.
As the conditions around them became drier and naturally-occurring fires started becoming more common, our ancestors began to harness the phenomenon during their search for and preparation of food. Rather than fire being an accidental or serendipitous discovery, the study authors believe that an altered landscape may have turned early humans into active pyrophiles.
Our ancestors likely would have taken advantage of natural fires
Parker’s team developed models using the optimal foraging theory to hypothesize what kinds of benefits a fire-altered landscape would provide early humans. They found that, thanks largely to the increased resources and energy provided by fire’s use, our ancestors would have been able to travel much farther, and it probably helped them expand into other parts of the world.
The new study contradicts other hypothetical scenarios, including one that suggests the first fire was the result of a spark, created by pounding rocks together, which spread to a nearby bush. As Kristen Hawkes, a professor of anthropology at Utah and senior author of the new study, pointed out in a statement , however, such proposals come up short.
“The problem we’re trying to confront is that other hypotheses are unsatisfying. Fire use is so crucial to our biology, it seems unlikely that it wasn’t taken advantage of by our ancestors,” she explained. “All humans are fire-dependent. The data show that other animals and even some of our primate cousins use it as an opportunity to eat better; they are essentially taking advantage of landscape fires to forage more efficiently.”
The scenario proposed by her team is the first to suggest that fire use was not a happy accident, and that early members of the genus Homo had to adapt to their increasingly arid and fire-prone surroundings. They reconstructed the tropical climate and vegetation that would have existed in Africa roughly 2-3 million years ago, and found evidence that allowed them to develop this new proposed scenario.
Fire would have made food easier to find, chew and digest
Recent carbon analyses of soils from this era found in parts of Ethiopia and Kenya suggest that woody plants were giving way to more tropical, fire-prone grasses between 3.6-1.4 million years ago, Parker, Hawkes and their fellow researchers explained.
When combined with drier conditions and a reduction in atmospheric carbon dioxide levels, this resulted in an increased frequency of naturally-occurring fires. This trend, in turn, led ancestral humans to take advantage of its benefits, adapting to eat grassland plants and foods that had been cooked in these flames, according to the study authors.
Ultimately, early humans began to see how they could take advantage of the benefits of fire, such as the way that it exposed previously hidden holes and animal tracks, thus reducing the time they needed to spend searching for food. Furthermore, they learned that foods which had been burned were easier to chew, and in some cases, their nutrients were easier to digest.
“Evidence shows that other animals take advantage of fire for foraging, so it seems very likely that our ancestors did as well,” said Hawkes. “This scenario tells a story about our ancestors’ foraging strategies and how those strategies allowed our ancestors to colonize new habitats. It gives us more insight into why we came to be the way we are; fire changed our ancestors’ social organization and life history.”
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