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Isotopic, Genetic Analysis Gives Insight Into Human Mobility During Neolithization

NEW YORK – As the Pre-Pottery Neolithic period progressed, people in southeastern Anatolia and the southern Levant became less mobile, according to a recent combined isotopic and DNA analysis.

During this period, people near the Fertile Crescent are thought to have shifted from a largely mobile life centered on hunting to a more sedentary one that relied on plant and animal domestication, though there has been limited data from southeastern Anatolia.

A team led by researchers at the Ludwig Maximilian University of Munich and the Max Planck Institute for Evolutionary Anthropology conducted strontium, carbon, and oxygen isotope analyses of 28 human and 29 animal remains from Nevalı Çori, a key site representing the T-shaped pillar society that emerged during Neolithization in what is now Turkey. They combined that data with genome-wide ancient DNA analyses from six individuals from Nevalı Çori and Ba'ja, a site in what is now Jordan. As they reported in the Proceedings of the National Academy of Sciences on Monday, the researchers began to piece together how mobility changed in the region after the first stages of the Pre-Pottery Neolithic period B (PPNB).

"Based on the results of our isotopic data and the newly integrated timescale of Nevalı Cori, a decline in mobility and growing reliance on domesticates took place by ca. 8300 BC at the end of its first subphase of the PPNB," senior author Philipp Stockhammer, a professor of archaeogenetics at LMU, and his colleagues wrote.

The researchers conducted strontium isotope analyses of human remains recovered from Nevalı Çori, which they compared to the geological background and the strontium levels found in fauna like pigs and foxes from the region. Based on the ratio of strontium isotopes, they noted a decline in mobility among inhabitants of Nevalı Çori, as there were fewer nonlocals present during the transition from PPNB I to PPNB II.

At the same time, carbon and oxygen isotope analysis suggested that the inhabitants of Nevalı Çori had a largely vegetarian diet, with increasingly limited consumption over time of hunted animals like gazelles, possibly reflecting a shift from hunting and gathering to more limited mobility and subsistence farming.

Meanwhile, the researchers also generated genome-wide sequence data from six individuals from Nevalı Çori and Ba'ja. Through principal components analysis and analyses of relatedness, the researchers uncovered genetic distinctions between the individuals from Nevalı Çori and Ba'ja, with the PPNB Nevalı Çori individuals exhibiting closer genetic relatedness to Anatolian hunter-gatherers, PPN farmers, and a Levantine cluster of PPN and Epipaleolithic individuals. The PPNB Nevalı Çori individuals, though, also showed genetic relatedness with Early Holocene Iranian and Caucasian hunter-gatherers.

The researchers additionally examined parental relatedness among their samples to find increasing runs of homozygosity, suggesting a diminished mating pool among individuals from later time points.

These findings suggest that during the early stages of Neolithization, there was a diverse gene pool at Nevalı Çori, reflecting interconnectedness within the Fertile Crescent. However, at the PPNB Ba'ja site and the later Iron Age Nevalı Çori, there was increased evidence of consanguinity.

"The evidence of consanguinity in the late PPNB Ba'ja further raises the question of how the PPN societies were internally organized and calls for additional future analyses on potential endogamy in the sense of cultural behavior and social practice," the researchers wrote.