The logical argument that ancient human ancestors had to have mastered fire before departing balmy Africa for the often freezing climes of Europe is being challenged by a review revealing that there is no evidence to support the idea.
Exactly when fire became a tool in the hominin toolbox is a thorny issue. Unlike stone tools, which hold together reasonably well over the course of time and can be dated as having been in hominin hands for at least 2.6 million years, the ash and charcoal that are often the only remains from ancient fires are rare in the fossil record as they are easily destroyed by the elements.
Yet because fire makes food so much more energy efficient to consume and has such a key role in providing warmth, most anthropologists have agreed that hominins had to have mastered fire before they headed into Europe.
"We assumed fire had to be an element of the human toolkit to survive northern-latitude winters," says archaeologist, Francesco d'Errico at the University of Bordeaux in France.
As logical as the argument seems, the review, published today in Proceedings of the National Academy of Sciences1, suggests that it is wrong.
Wil Roebroeks at Leiden University in the Netherlands and Paola Villa at the University of Colorado Museum in Boulder, searched the European archaeological record for fires and found that the earliest possible evidence comes from two 400,000-year-old sites, one in England that seems to have the remains of an ancient hearth and one in Germany that has a charred wooden tool and heated flint present. Older sites in England, Italy and Spain showed no evidence of fire mastery. These observations are problematic because ancient human ancestors migrated into the cold European climate more than a million years ago, implying that they survived for 600,000 or so without fire.
Further analysis allowed Roebroeks and Villa to construct a dataset of sites showing good evidence of fire use over the past 400,000 years. Indeed, they identify 400,000 years ago as the point at which evidence of fire in the European fossil record starts to increase significantly.
Their work is not just challenging when fire was used, it is also altering views of who was using it. The pair found that fire was actually rather common at sites where Neanderthals lived. "We were surprised to find so many Neanderthal sites with clear and repeated evidence of fire, since archaeologists believe that they did not habitually use it," says Roebroeks.
Fanning the flames
The findings conflict with data from other parts of the world. In Israel, at the Acheulian site of Gesher Benot Ya'aqov, researchers have used heated microartefacts and plant remains to propose that controlled fires were being burned at the site as many as 780,000 years ago. And there are some controversial suggestions that controlled fires were in use in Africa 1.6 million years ago.
Although the Israeli site is an enigma, Roebroeks and Villa argue that the early fires detected in Africa may have formed through lightning strikes. In some cases these may have been collected by hominins who knew how useful fire could be but had no idea how to create it on their own.
"Distinguishing 'captured' fire versus fire made at will by hominins is problematic in old archaeological contexts," says palaeoanthropologist Lawrence Straus at the University of New Mexico in Albuquerque. "The review raises the question of how early European hominins managed to survive winters," adds Straus.
On a grander scale, fire is often evoked as a key factor in helping humans to evolve – by allowing them to spend less energy digesting and more thinking. "As things stand, their evidence, or lack thereof, really questions this ambitious theory, that fire made humans," says Straus.