Researchers at the Weizmann Institute of Science reveal in an article published in Proceedings of the National Academy of Sciences an advanced and innovative method they have developed and used to detect non-visual traces of fire dating back at least 800,000 years, one of the earliest known evidence of the use of fire.
The newly developed technique may be a push towards a more scientific and data-driven type of archaeology, but - perhaps more importantly - it could help us better understand the origins of human history, our most basic traditions, and our experimental and innovative nature.
The controlled use of fire by ancient hominids - a group that includes humans and some of our extinct relatives - is thought to date back at least a million years, around the time archaeologists believe that Homo habilis began its transition to Homo erectus .
This is not a coincidence, as the working theory is that the use of fire was essential in our evolution, not only to allow hominins to keep warm, make advanced tools and protect themselves from predators, but also to acquire the ability to cook. Cooking meat not only kills pathogens, but also increases the efficiency of protein digestion and its nutritional value, paving the way for brain growth.
The only problem with this hypothesis is the lack of data:since the search for archaeological evidence of pyrotechnics is based mainly on the visual identification of the modifications resulting from the combustion of the objects (mainly, a change in color), the traditional methods have managed to find widespread evidence of the use of fire no older than 200,000 years. Although there is some evidence of fire dating back 500,000 years, it remains scant, with only five archaeological sites worldwide providing reliable evidence of ancient fire.
We may have found the sixth site says Dr. Filipe Natalio of Weizmann's Department of Plant and Environmental Sciences, whose previous collaboration with Dr. Ido Azuri of Weizmann's Nucleus of Life Facilities Department and his colleagues laid the groundwork for this project . Together they pioneered the application of AI and spectroscopy in archeology to find evidence of the controlled burning of stone tools dating between 200,000 and 420,000 years ago in Israel.
Now they are back, joined by doctoral student Zane Stepka, Dr. Liora Kolska Horwitz of the Hebrew University of Jerusalem, and Professor Michael Chazan of the University of Toronto, Canada. When we started this project , says Natalio, the archaeologists who have analyzed the finds from the Evron quarry told us that we would not find anything. We should have made a bet .
The Evron Quarry, located in the western Galilee, is an open-air archaeological site that was first discovered in the mid-1970s. During a series of excavations carried out at the time and led by Professor Avraham Ronen, archaeologists dug 14 meters deep and discovered a large number of animal fossils and Palaeolithic tools dating from between 800,000 and 1 million years ago, making it one of the oldest sites in Israel . None of the finds from the site or the soil in which they were found had any visual evidence of heat:ash and charcoal degrade over time, eliminating the chance of finding visual evidence of combustion. So if Weizmann's scientists wanted to find evidence by fire, they had to look further.
The expedition began with the development of a more advanced AI model than the one they had previously used. We tested a variety of methods, including traditional data analysis methods, machine learning models, and more advanced deep learning models says Azuri, who led the development of the models. The deep learning models that prevailed had a specific architecture that outperformed the others and successfully gave us the confidence we needed to continue using this tool in an archaeological context that had no visual signs of fire usage . The advantage of AI is that it can find hidden patterns at many scales. By pinning down the chemical composition of materials down to the molecular level, the model output can estimate the temperature to which stone tools were heated, ultimately providing insights into past human behaviors.
With a precise AI method in hand, the team was able to start looking for molecular signatures of the stone tools used by the inhabitants of the Evron quarry nearly a million years ago. To do this, the team evaluated the heat exposure of 26 flint tools found at the site almost half a century ago. The results revealed that the tools had been heated to a wide range of temperatures, some of them exceeding 600ºC. Furthermore, using a different spectroscopic technique, they analyzed 87 faunal remains and found that the tusk of an extinct elephant also exhibited structural changes due to heating. Although they are cautious in their statement, the presence of hidden heat suggests that our ancient ancestors, like scientists themselves, were experimentalists.
According to the research team, by looking at archeology from a different perspective, using new tools, we could find much more than we initially thought. The methods they have developed could be applied, for example, to other Lower Palaeolithic sites to identify non-visual evidence of the use of fire. Furthermore, this method could perhaps offer a renewed spatio-temporal perspective on the origins and controlled use of fire, helping us better understand how hominin behaviors related to pyrotechnics evolved and drove other behaviors. Especially in the case of primitive fire , says Stepka, if we use this method on archaeological sites one or two million years old, we might learn something new .
By all accounts, the expedition was a resounding success. It wasn't just a demonstration of exploring and being rewarded for the knowledge gained , says Natalio, but the potential that exists in the combination of different disciplines :Ido has a background in quantum chemistry, Zane is a scientific archaeologist, and Liora and Michael are prehistorians. By working together, we have learned from each other. For me, it is a demonstration of how scientific research should work between the humanities and science .