First flames: earliest man-made fire found?

In the stereotypical view of prehistory, fire is important. We imagine caveman and cavewoman gathering around a cavefire to heat their cavehouse. In our minds eye fire was a key part of prehistoric life and this mental image is surprisingly close to the truth.

Fire was indeed an important part of our cultural evolution. It allowed us to extend daylight hours artificially and efficiently process a wider range of foods. That would have undoubtedly had a large impact on both our biology and our behaviour.

Although some people do overplay how important fire was, linking cooked food to the evolution of our brain (an idea with little evidentiary support), it was still an important technological achievement nonetheless. As such, finding out when man became lord of the flame is a crucial part in understanding our technological evolution.

Which makes Ice Age a serious piece on human evolution, right?

Finding out when people started to use fire is very easy in one respect but awfully difficult in another. On the one hand fire leaves behind ash which, provided it isn’t scattered, will typically form a very distinct band in the stratigraphy of a site which archaeologists can easily see. Thus finding when and where fire happened isn’t that hard.

However, understanding the “how” of fire is a lot more difficult. How did the fire form? Were the people able to start the fire or did they just steal a burning bush from a wildfire and cultivate it? These questions are a lot harder to answer because both natural-caused and man-caused fire produce the same residue – ash.

One good measure of whether a fire was man-made or simply a natural occurrence (which was then harnessed by people) is the frequency of fires at  particular site. If they are common then its a good sign they aren’t simply exploiting bushfires because they are infrequent.

A stratigraphic cross-section of a neanderthal cave in France (Roc de Marsal). Note the distinct darker bands of ash around the number 6.

Such rigorous evidence of fire use was found at the Roc de Marsal cave shelter in France. This neanderthal site has multiple hearths, dating to between 71 and 91 thousand years ago. It would seem hominins could control fire by at least this date.

Less secure (but still relatively reliable) evidence can push this date back to ~300,000 years ago when hominins started using fire to alter their tools. Possible hearths have also been recovered from this date although they provide little information on whether the hominins were controlling natural fire or producing it of their own accord.

There is circumstantial evidence suggesting hominins used fire as early as 800,000 years ago. At the Israeli site of Gesher Benot Ya’aqov burnt material is found in clusters. Perhaps these clusters represent fires, although none of the actual fires have been found. Further, there are only a handful of these clusters and so they may have just been exploiting natural fire.

However, a new South African site purports to add definite evidence to this tale; claiming hominins were controlling fire there as early as 1 million years ago!

Wonderwerk’s location, where these claims of early fire come from

This site contains a number of animal bones, representing at a minimum 295 individuals killed. 43.7% of these have been discoloured due to fire. Whilst that is a large proportion there is always the chance a natural wildfire burned them and they were simply carried into the cave by people. After all, a large number of animals would be killed in a wildfire.

However, this is probably not the case. They looked at the sediment from the area of the site with the most burnt bone and found that it displayed the properties expected if that rock had been heated to between 400-700 degrees centigrade – the same temperature the bones would have to be heated to to produce the discolouration.

Thus it seems extremely likely that these bones were burnt at that location. Further, rocks which don’t naturally occur at there (so would have to have been brought in) also show evidence of being burned at these temperatures. The common element between the native burnt rock and this imported burnt rock, confirming that the fire did occur in that cave.

Bone from the site discoloured by burning

So fire was there, were hominins? In a word: yes. The site contains several Acheulean tools indicating occupation by a member of the genus Homo between ~1.8-0.2 million years ago. Of course, that doesn’t really tell us anything useful. Going by tools alone it could have been made by Homo erectus or H. heidelbergensis. It might even have been made by Homo sapiens. It could be controversial or not…we need a more specific date!

Luckily they dated the sediment via radiometric decay of Aluminium and found that the fire occurred in layers dating to ~0.99 million years ago (+/- 0.19 my). This is within the time of Homo erectus, indicating that species had the ability to control fire! These aluminium dates were checked against magnetic reversal data.

At certain points in the earth’s past the magnetic field was facing the opposite direction. By dating rocks with evidence of this magnetic reversal a chronology can be built up. These aluminium dates are consistent with the magnetic reversal chronology, with the 0.99 million year old rocks having the expected magnetic orientation a 0.99 million year old rock should have.

However, most (80%) of the burned specimens come from a single part of the cave (the part they found had been burned to ~500 degrees). This could indicate that weren’t that many ignition events after all and whilst H. erectus  could control fire it did not start them, exploiting infrequent natural fires.

Of course, that alternate explanation isn’t confirmed either, its just a grain of salt with which these conclusions must be taken. I would also ideally like a variety of methods used to date the site: one or two can always be biased. Multiple methods are less likely to be.

Stone from the cave (a) compared with experimentally heated stone to see if they are similar

Overall there is good evidence fire occurred in this cave and that it was indeed controlled. This happened during the time of Homo erectus, ~1 million years ago. Whether they were also able to create the fire isn’t confirmed but does seem likely given the large amount of material burned within the cave.

As such this site provides confirms that Homo erectus had both the ability to control and create fire by this point in time. This is the earliest solid evidence we have for this behaviour making it a very important site.

Berna F, Goldberg P, Horwitz LK, Brink J, Holt S, Bamford M, & Chazan M (2012). Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proceedings of the National Academy of Sciences of the United States of America PMID: 22474385