Notable paper: Eerkens J et al. 2016. Isotopic and genetic analyses of a mass grave in central California: Implications for precontact hunter-gatherer warfare. American Journal of Physical Anthropology 159:116–125.
Synopsis: Jelmer Eerkens and colleagues examined a mass burial of seven men from the Amador Valley of California around 850 AD. The people in the area at this time were sedentary hunter-gatherers living in small villages, and these seven men appear to have been killed in a violent event. Eerkens and colleagues were able to investigate stable isotopes in the bodies to show that the men came from outside the Amador Valley, and mtDNA established that the men were not close maternal relatives. Further, a slight contrast in the carbon and strontium stable isotopes between bone and teeth shared by the men suggest that they all changed residence locations, possibly together, some time after their third molars finished enamel deposition.
Interesting because: The burial is evidence of intergroup warfare or raiding during a time of population growth and increased sedentism. As discussed in the paper, this is one of several known examples of mass graves of males with non-local isotopic signatures. The precontact trajectory of California populations included episodes of population growth when larger villages fissioned, with groups finding new residences in less crowded locations. This burial documents one of the consequences of such population growth, a costly one for the village that lost a large fraction of its males in a raid or battle.
Beyond California: This is a nice example of the kind of insight that becomes possible when scientists develop a stable isotope dataset encompassing many burials across a region from a range of times and geographic locations. California is a valuable area for such research because it was an area within the Americas with a complex landscape of resource availability for human populations that depended upon foraging for wild foods. The pattern of increased sedentism and village life is comparable to later Upper Paleolithic and Mesolithic contexts in Europe, and pre-agricultural settings in western Asia.