Researchers find one of the earliest pieces of evidence supporting the use of fire using cutting-edge AI methods.
There’s a saying that where there’s smoke there’s fire, and researchers at the Weizmann Institute of Science are working hard to investigate that claim, or at least define what “smoke” is. In a recently published article, the researchers describe a cutting-edge, groundbreaking technique they developed and used to find unseen signs of fire dating back at least 800,000 years, one of the earliest known evidence of the use of fire in Proceedings of the National Academy of Sciences.
The newly created method could help push archeology toward a more data-driven, scientific approach, but perhaps more importantly, it could help us understand the beginnings of human history, our most basic traditions, and our propensity for experimentation and innovation.
Archaeologists believe that Homo habilis began to evolve into Homo erectus around the time ancient hominins, a group that includes humans and some of our extinct family members, first used fire in a controlled manner. It is believed that this happened about a million years ago. This is no coincidence, as the “Cooking Hypothesis,” the working theory, holds that the use of fire played a crucial role in human evolution, allowing hominins not only to stay warm, craft sophisticated tools, and ward off predators, but also to develop the ability to cook.
Cooking meat not only eliminates pathogens, but also increases efficient protein digestion and nutritional value, paving the way for brain growth. The only problem with this hypothesis is a lack of data: since finding archaeological evidence of pyrotechnology relies primarily on visually identifying modifications resulting from the burning of objects (mainly a color change), traditional methods have succeeded in becoming widespread Evidence of the use of fire found no older than 200,000 years.
Although there is some evidence of fires dating back as far as 500,000 years ago, it is sparse, with only five archeological sites around the world providing reliable evidence of an ancient fire.
“Perhaps we have just found the sixth location,” says Dr. Filipe Natalio von Weizmann’s Plant and Environmental Sciences department, whose previous collaboration with Dr. Ido Azuri von Weizmann’s Life Core Facilities department and colleagues formed the basis for this project.
Together they pioneered the use of AI and spectroscopy in archeology to find evidence of the controlled burning of stone tools from 200,000 to 420,000 years ago in Israel. Now they’re back, along with graduate student Zane Stepka, Dr. Liora Kolska Horwitz from the Hebrew University of Jerusalem and Prof. Michael Chazan from the University of Toronto, Canada.
The team upped the ante by going on a ‘fishing expedition’ – casting far out in the water and seeing what they could catch. “When we started this project,” says Natalio, “the archaeologists who analyzed the finds from the Evron quarry told us that we would not find anything. We should have bet.”
The Evron Quarry in the western Galilee is an open-air archaeological site first discovered in the mid-1970s. During a series of excavations that took place at the time and led by Prof. Avraham Ronen, archaeologists dug down 14 meters and uncovered a wide range of animal fossils and Palaeolithic tools dating between 800,000 and 1 million years old, making them one of the oldest sites in Israel.
None of the finds from the site or soil in which they were found showed visible signs of heat: ash and charcoal decompose over time, eliminating the likelihood of finding visual signs of combustion. So if the Weizmann scientists wanted to find evidence of fire, they had to look further.
The “Fishing” expedition began developing a more advanced AI model than 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 prevailing deep learning models 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 with no visible evidence of fire use.” The advantage of AI is there in that it can find hidden patterns on a variety of scales. By pinpointing the chemical composition of materials down to the molecular level, the model output can estimate the temperature to which the stone tools were heated, ultimately providing information about past human behavior.
With an accurate AI method in hand, the team could begin fishing for molecular signals from the stone tools used by the residents of Evron Quarry nearly a million years ago. To do this, the team assessed the heat stress of 26 flint tools found at the site nearly half a century ago.
The results showed that the tools had been heated to a wide range of temperatures – some in excess of 600°C. They also analyzed 87 animal remains using a different spectroscopic method and found that the tusk of an extinct elephant also showed structural changes due to heating. Although their claim is cautious, the presence of hidden heat suggests that our ancient ancestors, like the scientists themselves, were experimenters.
If we look at archeology from a different perspective and use new tools, we may find a lot more than we initially thought, according to the research team. For example, the methods they developed could be applied to other Upper Paleolithic sites to identify unseen evidence of the use of fire. In addition, this method could perhaps provide a renewed spatiotemporal perspective on the origins and controlled use of fire, and help us better understand how hominin pyrotechnic behavior evolved and influenced other behaviors.
“Especially with the early fire,” says Stepka, “if we apply this method to archaeological sites that are one or two million years old, we might be able to learn something new.”
In any case, the fishing expedition was a complete success. “It was not only a demonstration of exploration and rewarding knowledge gained,” says Natalio, “but also of the potential that lies in combining different disciplines: Ido has a background in quantum chemistry, Zane is a scientific archaeologist, and Liora and Michael are prehistorian. By working together we have learned from each other. For me it is a demonstration of how scientific research should work in the humanities and sciences.”
“Hidden signatures of early fire at Evron Quarry (1.0 to 0.8 Mya)” by Zane Stepka, Ido Azuri, Liora Kolska Horwitz, Michael Chazan and Filipe Natalio, June 13, 2022, Proceedings of the National Academy of Sciences.
The study was funded by the Yeda-Sela Center for Basic Research.
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