Plaque Found on 400,000-year Old Teeth Shows Caves Had Dirty Air

Discovery shows early humans suffered from smoke inhalation due to burning fires and roasting meat in caves.

Prof. Israel Hershkovitz

Man-made air pollution is not a modern invention or a corollary of the Industrial Age. A new discovery at the Kessem cave near Rosh Ha’ayin shows that that this is a prehistoric phenomenon which has accompanied humans for 400,000 years. According to this discovery, even early humans suffered from the impact of smoke inhalation, caused by burning fires and roasting meat inside their caves.

Researchers from Tel Aviv University, in collaboration with an international team of researchers, have managed to extract some plaque from three teeth of humans who lived 400,000 years ago. Analysis of the plaque revealed particles of soot that were trapped underneath this plaque and covered by it. Along with the soot particles, the researchers also obtained evidence for the consumption of plants, and even found parts of a moth wing. They found 13 teeth in the cave, three of which provided plaque. The teeth belonged to an unidentified species of humans who lived in the area at that time.

The plaque, which was extracted using advanced laboratory methods, yielded important information. “This is the first and earliest direct evidence for the eating of plants,” explains Prof. Ran Barkai from TAU. He added that the prevailing hypothesis is that the early human diet was based on both meat and plants.

Damage from air pollution

The other important discovery was the damage inflicted by manmade pollution. “This is the earliest evidence for air pollution created by man, which caused him harm. Humans were familiar with fire much earlier, with sporadic testimony supporting this, but they did not use it for cooking food on a daily basis until 400,000 years ago. As soon as they learned how to control fire they used it for roasting food, allowing them to obtain more calories from each portion of meat. However, they paid for this with their health. The soot particles in their plaque indicate that the roasting was done inside caves, leading to smoke inhalation. As in other cases, progress was associated with environmental damage. We can assume that smoke inhalation affected their health, leading them to seek creative solutions, as we’ve been trying to do since then,” says Barkai.

(Credit: Prof. Israel Hershkovitz)

The Kessem cave has been excavated since 2000 by researchers from the archaeology department at TAU, yielding a string of important discoveries. The new work was carried out by Barkai along with Prof. Avi Gopher and Dr. Rachel Sarig from TAU, in collaboration with Prof. Karen Hardy from ICREA, the Catalan Institution for Research and Advanced Studies, Anita Radini and Stephen Buckley from York University and Les Copeland from The University of Sydney. The results of their work appeared in Quaternary International.

“The Kessem cave represents an unusual stage in the biological and cultural evolution of humans,” explains Gopher. “This stage, between 200,000 and 400,000 years ago, lasted for 200,000 years. Similar sites are scattered around the whole southern Levant, from Kessem to Syria, but this cave is unparalleled in its degree of preservation.” The earliest consistent use of fire for roasting meat was found in this cave, as well as the earliest evidence for re-use of vessels, and the earliest evidence for a human species that was the forebear of all modern humans in our region. This concept challenges the prevailing view that claims that the origins of intelligent humans were in eastern Africa.

The teeth in the cave do not come from homo sapiens, modern humans, who have only been around for 30,000 years. They also do not fit known characteristics of homo erectus, considered to be the forebear of homo sapiens and of Neanderthal man, who lived around 1.5 million years ago. “We don’t exactly know what species this was, we only know which one it wasn’t,” explains Barkai. “It’s not modern man or homo erectus. This is a human with some characteristics of homo sapiens and Neanderthal man – it could be a local link in the chain of evolution.”

High-calorie elephants - gone

Scientists believe that a possible cause of the biological and cultural changes undergone by the cave’s inhabitants, including the adoption of meat roasting, was the disappearance of elephants from the local diet. “Different species of humans lived here for a million years, eating elephants,” says Barkai. “400,000 years ago, elephant bones disappeared from sites of human habitation and activity. An elephant is an amazing bundle of calories. We calculated that from a nutritional perspective, one elephant is equivalent to at least 80 fallow deer. The disappearance or extinction of elephants forced humans to adapt to a new environment, biologically and culturally. There was an advantage to light-footed humans with well-developed cognitive functioning. These changes prompted the use of fire for roasting meat, in order to extract more calories from the deer.”

The idea of trying to extract plaque from teeth found in the cave came from an article describing findings from the plaque of 50,000-year-old Neanderthals found in Europe. “To do this we contacted Prof. Hardy, who uses state-of-the art technology to extract plaque form such teeth,” says Barkai. “She was initially skeptical, since no one had ever worked on 400,000-year-old teeth, but ultimately she managed to extract plaque from three of them. Subsequently, using a complex chemical process, we were able to investigate what lay between the teeth when the plaque was formed, and the results were very surprising.”