The origin of human violence and warfare is controversial, and some scholars contend that intergroup conflict was rare until the emergence of sedentary foraging and complex sociopolitical organization, whereas others assert that violence was common and of considerable antiquity among small-scale societies. Here we consider two alternative explanations for the evolution of human violence: (i) individuals resort to violence when benefits outweigh potential costs, which is likely in resource poor environments, or (ii) participation in violence increases when there is coercion from leaders in complex societies leading to group level benefits. To test these hypotheses, we evaluate the relative importance of resource scarcity vs. sociopolitical complexity by evaluating spatial variation in three macro datasets from central California: (i) an extensive bioarchaeological record dating from 1,530 to 230 cal BP recording rates of blunt and sharp force skeletal trauma on thousands of burials, (ii) quantitative scores of sociopolitical complexity recorded ethnographically, and (iii) mean net primary productivity (NPP) from a remotely sensed global dataset. Results reveal that sharp force trauma, the most common form of violence in the record, is better predicted by resource scarcity than relative sociopolitical complexity. Blunt force cranial trauma shows no correlation with NPP or political complexity and may reflect a different form of close contact violence. This study provides no support for the position that violence originated with the development of more complex hunter-gatherer adaptations in the fairly recent past. Instead, findings show that individuals are prone to violence in times and places of resource scarcity.warfare | prehistoric violence | North America

Inspired by Stine's [1994. Extreme and persistent drought in California and Patagonia during Mediaeval Time. Nature 369, 546-549.] findings from Mono Lake and Graumlich's [1993. A 1000-year record of temperature and precipitation in the Sierra Nevada. Quaternary Research 39, 249-255.] tree-ring study from the southern Sierra Nevada, California archaeologists have for over a decade been investigating the possibility that prehistoric societies were noticeably impacted by severe droughts during the Medieval Climatic Anomaly (MCA; cal A.D. 800-1350). Decreased production at obsidian sources, dramatic increases in bead production, trade, and sociopolitical complexity in the Channel Islands, and subsistence changes on the central coast were among the trends attributed to drought-related demographic stress by researchers in the 1990s. Review of more recent archaeological research shows that as the search for signs of unusual cultural changes during the MCA has broadened, some of these early patterns (e.g. violence and health problems) have been found to be more complicated and regionally varied than previously thought while others (e.g., settlement disruption, deterioration of long distance trade, and population movements) have been further corroborated.

a b s t r a c tSpatial and diachronic patterns in skeletal evidence for three forms of violence were evaluated for central California with information from a bioarchaeological database that contains information on 16,820 buri als from 329 sites. The most abundant form of violence was sharp force/projectile trauma (462/6278, 7.4%), followed by blunt force craniofacial trauma (264/6202, 4.3%) and trophy-taking/dismemberment (87/12,603, 0.7%

We document evidence for trophy-taking and dismemberment with a new bioarchaeological database featuring 13,453 individuals from prehistoric central California sites. Our study reveals 76 individuals with perimortem removal of body parts consistent with trophy-taking or dismemberment; nine of these individuals display multiple types of trophy-taking and dismemberment for a total of 87 cases. Cases span almost 5,000 years, from the Early Period (3000-500 BC) to the Late Period (AD 900-1700). Collectively, these individuals share traits that distinguish them from the rest of the population: a high frequency of young adult males, an increased frequency of associated trauma, and a tendency towards multiple burials and haphazard burial positions. Eight examples of human bone artifacts were also found that appear related to trophy-taking. These characteristics suggest that trophy-taking and dismemberment were an important part of the warfare practices of central Californian tribes. Temporally, the two practices soared in the Early/Middle Transition Period (500-200 BC), which may have reflected a more complex sociopolitical system that encouraged the use of trophies for status acquisition, as well as the migration of outside groups that resulted in intensified conflict. Overall, trophy-taking and dismemberment appear to have been the product of the social geography of prehistoric central California, where culturally differentiated tribes lived in close proximity to their enemies.

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Catastrophic decline of Indigenous populations in the Americas following European contact is one of the most severe demographic events in the history of humanity, but uncertainty persists about the timing and scale of the collapse, which has implications for not only Indigenous history but also the understanding of historical ecology. A long-standing hypothesis that a continent-wide pandemic broke out immediately upon the arrival of Spanish seafarers has been challenged in recent years by a model of regional epidemics erupting asynchronously, causing different rates of population decline in different areas. Some researchers have suggested that, in California, significant depopulation occurred during the first two centuries of the post-Columbus era, which led to a “rebound” in native flora and fauna by the time of sustained European contact after 1769. Here, we combine a comprehensive prehistoric osteological dataset (n = 10,256 individuals) with historic mission mortuary records (n = 23,459 individuals) that together span from 3050 cal BC to AD 1870 to systematically evaluate changes in mortality over time by constructing life tables and conducting survival analysis of age-at-death records. Results show that a dramatic shift in the shape of mortality risk consistent with a plague-like population structure began only after sustained contact with European invaders, when permanent Spanish settlements and missions were established ca. AD 1770. These declines reflect the syndemic effects of newly introduced diseases and the severe cultural disruption of Indigenous lifeways by the Spanish colonial system.