According to a study, an analysis of obsidian artifacts unearthed during the 1960s at two important archaeological sites in southwestern Iran reveals that the networks Neolithic people formed in the region as they developed agriculture were larger and more complex than previously thought.
The study, which was published on October 17 in the journal Proceedings of the National Academy of Sciences, is the first to apply state-of-the-art analytical tools on a collection of 2,100 obsidian artifacts housed in the Yale Peabody Museum.
The artifacts were discovered more than 50 years ago at Ali Kosh and Chagha Sefid, two sites on Iran’s Deh Luran Plain that yielded important Neolithic Era discoveries — the period beginning around 12,000 years ago when people began farming, domesticating animals, and establishing permanent settlements.
Analyses performed shortly after the items were discovered suggested that people first acquired the obsidian — volcanic glass — first from Nemrut Dağ, a now-dormant volcano in Eastern Turkey, and then from an unknown second source. This new elemental analysis showed the obsidian came from seven distinct sources, including Nemrut Da in modern-day Turkey and Armenia, which is up to 1,000 miles away from the excavation sites on foot.
“It wasn’t a simple pattern of people obtaining obsidian from one source and then shifting to the next,” said Ellery Frahm, an archaeological scientist in the Department of Anthropology in Yale’s Faculty of Arts and Sciences, and the study’s lead author. “Rather, our analysis shows that they were acquiring obsidian from an increasingly diverse number of geological sources over time — a trend that was impossible to detect with the technology and methods available 50 years ago.”
The new analysis, combined with computer modeling, indicates that there were intensifying connections among Neolithic people, implying the presence of a greater number of settlements between the source volcanoes and the two sites where the artifacts were found thousands of years later, Frahm added.
The objects were discovered during multiple excavations at the two sites led by Frank Hole, Yale’s C.J. MacCurdy Professor Emeritus of Anthropology. The initial analyses were largely based on the appearance of the artifacts, specifically their color when held up to the light. A subset of 28 artifacts were then subjected to an elemental analysis method common at the time that involved grinding them into powder.
Frahm and coauthor Christina M. Carolus, a doctoral student in the Department of Anthropology, are the first to study the elemental composition of obsidian artifacts since these earlier analyses. They used state-of-the-art portable X-ray fluorescence instruments, which allowed them to examine the entire collection without damaging the artifacts.
“Every aspect of the discoveries made at these sites had been revisited since the 1960s except the elemental composition and sourcing of the obsidian artifacts,” Carolus said. “A lot more is known about the source volcanoes today than 50 years ago, and we know that sorting obsidian by color will miss a lot of nuances. Fortunately, we have instruments the size of cordless drills that, in a matter of seconds and without destroying material, give us a more accurate elemental signature than anything that was possible in the past.”
Scientists widely believed that humanity’s transition from the hunter-gatherer lifestyle to agriculture produced a period of rapid population growth due to the increased birth rates made possible by enhanced food supplies and permanent settlements. Finding evidence of this demographic shift often requires excavating locations that include burial sites, which can indicate the population of a given settlement and provide a clearer picture of how agriculture allowed people to disperse across a landscape, according to Frahm. The researchers’ analysis of the obsidian yielded similar results.
“Tracing these obsidian artifacts from their sources to their endpoints offers insight into how they moved from hand to hand to hand over time, which helps us better understand population changes in the region during the Neolithic Era,” Frahm explained. “It suggested there were larger social networks and more settlements between the source volcanoes and the excavation sites than we previously thought.” — Yale University
