Africa– It is seen as one of the key steps in human evolution and gave our species the opportunity to control their environment for the first time.
But fire may have first being used by our early human ancestors to help them forage for food far earlier than previously believed, according to a new theory.
Natural blazes in the African landscape 2 to 3 million years ago could have shaped our species by making them increasingly dependent upon fire, forcing them to learn how to control it.
It would also have cooked any creatures unfortunate enough to get caught up in the flames, providing a source of meat that was easy to scavenge and digest.
Similarly roots, tubers and other plant material would have been cooked in the flames, making them edible for early humans.
Professor Kristen Hawkes, an anthropologist at the University of Utah who is the senior author of a new paper setting out the hypothesis, said Africa was much more fire prone 2 to 3 million years ago.
The environment dried out meaning grass and bushes were easily set alight, so natural fires occurred far more frequently.
This could have provided a boon to early Homo species living in the continent at the time, and as they adapted to fire prone environments became reliant upon it.
It contrasts with other theories that suggest humans discovered fire as a result of pounding rocks that produced a spark.
Many anthropologists believe early humans such as Homo erectus first began exploiting fire 1.5 million years ago, while others say our ancestors first began controlling 350,000 years ago.
Instead Professor Hawkes and her colleagues say early humans may have learned how to control fire earlier than that after first becoming reliant upon the foraging opportunities presented by natural fires.
If correct, the findings could mean that early species of human ancestor, like Homo habilis were exploiting fire and by doing so shaped the course of human evolution as later species like Homo erectus developed smaller teeth and jaws, perhaps because they were eating cooked food.
Professor Hawkes said: ‘All humans are fire-dependent.
‘The problem we’re trying to confront is that other hypotheses are unsatisfying.’
‘Most people think the logical reaction would be to run away from fire, but fire provided our ancestors with a feeding opportunity.
‘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.
‘Fire use is so crucial to our biology, it seems unlikely that it wasn’t taken advantage of by our ancestors.’
Professor Hawkes and her colleagues reconstructed the climate and vegetation in Africa between 2 to 3 million years ago.
Recent carbon analysis of prehistoric soils from the Awash Valley in Ethiopia and Omo-Turkana basin in northern Kenya show a pattern of woody plants being replaced by more tropical, fire-prone grasses around 3.6 million to 1.4 million years ago.
At around this time the levels of carbon dioxide in the atmosphere were dropping and Africa was becoming increasingly arid.
Fossilised wood also found in Ethiopia from around the same period indicate conditions at the time were far drier.
The researchers said that as the ecosystem became more arid it would have fluctuated between woodland and open grasslands.
In the drier conditions, fires would have become more common and early human species would have needed to adapt to finding foods on the open grasslands.
The scientists, whose work is published in the journal Evolutionary Anthropology, used models of foraging to examine what impact this would have had on early humans.
They found that fires would have offered great gains in terms of allowing these early humans spend less time searching for and handling food.
Instead, they could have initially used natural fires to help them before learning how to control fires to burn off natural cover for themselves.
This would make it easier for them to find prey to hunt while foods caught up in the flames would take less effort to chew and digest.
Professor Hawkes and her colleagues said this could also explain the apparent lack of hearths and fires in the archaeological record from this time.
Cooking over a prepared hearth should leave traces at early human sites in the form of preserved material.
But if early humans were taking advantage of landscape burns, it would be indistinguishable from naturally occurring fires.
Professor Hawkes said by increasing the resources and energy available, fires also allowed our ancestors to travel greater distances and expand to other continents.
She said: ‘When our genus appears, almost immediately, those populations got out of Africa. If you look at the other great apes, they’re tied to habitats where juveniles can feed themselves.
‘We were able to expand out of Africa into Europe and Asia because our fire use not only earned higher return rates, but also permitted older women in these communities to help feed juveniles, thereby freeing our ancestors to move into habitats where youngsters couldn’t feed themselves.
‘This scenario tells a story about our ancestors’ foraging strategies and how those strategies allowed our ancestors to colonise 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.’
WHEN DID WE START COOKING?
Exactly when humans first began using fire to make their lives easier remains one of the most controversial topics in archaeology.
The earliest suggested date is around 1.5 million years ago.
However, some research suggests that our ancestors first began using fire to cook their food as far back as two million years ago.
Cooking meat played a vital role in human evolution, making it easier to digest, reducing the time it took to feed and requiring smaller teeth.
A study in 2011 by biologists at Harvard University, in Cambridge, Massachusetts compared the body patterns, DNA and other characteristics of modern humans, non-human primates and 14 extinct hominins.
They found used the information to look for patterns when eating time began to reduce.
They calculated that if humans were ordinary primates living off raw food, eating would take up 48 per cent of their day.
However, modern humans spend just 4.7 per cent of their day to food consumption.
They suggest that the evolution of smaller teeth in Homo erectus around 1.9 million years ago coincided with a change in diet that may have been driven by the cooking of food.
But recent discoveries of flint fragments in Mount Carmel, close to Haifa on the coast of northern Israel, have provided the oldest signs of humans controlling fire.