Research into early use of fire could help solve human evolution mystery

Archaeologists have taken a crucial step towards solving one of human evolution’s greatest mysteries.

More than two decades ago, a British scientist proposed that a major change in human anatomy, some 1.8 million years ago, had been generated by humanity’s discovery that it could use fire to cook food, thus making it more digestible.

The problem was that archaeologically, there was no scientific proof that humans even knew how to use fire, let alone cook with it before around 250,000 years ago.

But now, archaeologists from Israel and Canada have carried out new scientific research proving that early humans were using fire at least 900,000 years ago.

This remarkable new dating operation, in a prehistoric cave in South Africa, has now pushed human use of fire sufficiently far back in time to open the way for scientists to begin to contemplate that two even older African fire sites (in Kenya, dating back to 1.5 million and 1.6 million years ago) might also have been human campfires, rather than merely natural fires caused by lightning strikes.

The new roughly 900,000 BC secure date obtained by Israeli and Canadian scientists – at a cave on the southern edge of the Kalahari Desert  – is likely to completely revolutionise many pre-historians’ understanding of humanity’s early use of fire and consequently its potential role in human diet and evolution.

One of the world’s top experts on fire’s role in human evolution, Professor Richard Wrangham of Harvard University, says that the new South African secure early date is “extremely significant”.

“Pushing back early humanity’s proven use of fire will probably lead to a reassessment of other even earlier potential human campfire sites in Africa,” said Professor Wrangham.

“The South African discovery is a major step towards confirming that human exploitation of fire for cooking and defence did indeed drive key aspects of human evolution.

“I believe that early humans originally discovered how to use fire around 1.8 million years ago and that ability to cook food led to major otherwise inexplicable changes in human gut anatomy, dentition, facial shape and increased brain size that occurred at roughly that time.”

Although only one patch of early fire has been definitively discovered in the South African cave so far, there are hints there could be literally dozens of others scattered across the cave – and some of them are likely to be even older, dating back as far as the era of rapid evolutionary change 1.8 million years ago.

“Further excavation and dating research is now planned – but the work will be scientifically increasingly complex and is likely, therefore, to take several years,” said the co-director of the cave investigation project, Professor Michael Chazan of the University of Toronto.

The people who used the cave 900,000 years ago knew how to acquire and use fire – but probably did not yet know how to make it.

However, in sub-Saharan Africa (and indeed some other parts of the world) fire occurred naturally and very frequently – courtesy of lightning – in prehistoric times, as it still does today.

Gently burning grassland wildfires, generated by lightning strikes, can last for several days – and their smoke can be seen from many miles away. At certain times of the year (for instance, at the end of dry seasons) – and, in some places, intermittently throughout the year – such lightning-generated grassland wildfires are very frequent.

So early human acquisition of fire would have been relatively easy, once humanity had realised how useful fire could be –  to cook with, for protection against predators, to gain warmth from, to produce light and to socialise around.

Professor Wrangham, author of the key book on the subject (Catching Fire), believes that it is those economic and social uses which combined to speed up human evolution around 1.8 million years ago. It was that evolutionary spirit which led to the appearance of an early human species known as Homo erectus – the species from which most subsequent human species, including our own (Homo sapiens), evolved. Indeed, the early human species using fire in the cave was probably Homo erectus.

It may be particularly significant that archaeologists have found evidence of very early fire inside a cave.

Certainly the evidence from that South African cavern (Wonderwerk [Miracle] Cave near the small South African town of  Kuruman) suggests that, 900,000 years ago, humans weren’t necessarily using it as a regular habitation.

It is conceivable therefore that they were using it specifically or partly as a place to preserve fire.

Acquiring fire from wildfires was easy, but preserving it was more challenging – and weatherproof caves may have been essential for that fire preservation process.

One of the best ways of carrying and preserving fire is to collect burning animal dung left smouldering in the wake of a grassland wildfire. Slow-burning dung or charcoal may well have been taken back to caves by early humans because such portable fire sources could smoulder for many hours.

The Wonderwerk Cave excavation (co-directed by Dr Liora Kolska Horwitz of the Hebrew University of Jerusalem and Professor Chazan of Toronto) is revealing the lost secrets of ancient Africa – but it’s also helping to connect modern Africans to their extraordinarily archaeological heritage.

The cave, which 900,000 years ago was illuminated by ancient fire, is now being used not just for archaeological investigations, but also for public heritage outreach work by local people and by a unique South African theatre group.

The cave’s archaeology is helping to shed new light on human evolution – and the theatre group (‘Walking Tall’ based in Johannesburg’s Witwatersrand University) is using the cavern to stage educational plays to tell local Africans about their continent’s remarkable role as the birthplace of mankind.

The site itself is the world’s oldest known example of a cave being used by early humans. What’s more, it’s also the place with the world’s longest-lasting record of human activity. Humanity – from now-long-extinct prehistoric human species to modern humans – have intermittently used the cave for around two million years (indeed until the 1920s).

The chronological evidence from the site is “an important step towards understanding the tempo of human evolution across the African continent,” said Dr Horwitz.

Wonderwerk Cave extends for around 140m into the side of a hill. It has been intermittently studied by archaeologists since the 1940s. Around a decade ago, archaeological investigators published evidence suggesting that fire was being used in the cave a million years ago – but critics cast doubt on the date and suggested it was only half that age. The cave’s investigators then undertook further research, found additional early dating evidence and this week published their findings, finally proving that fire was used there around 900,000 years ago. What’s more, future research is likely to conclude that other fire sites within the cave are even older.

The new early fire date and other details about the cave are published this week in Quaternary Science Reviews and was funded by the Canadian Social Sciences and Humanities Research Council and the Johannesburg-based Paleontological Scientific Trust.