Fourteen adult burials in a large (N = 224) prehistoric central California cemetery (CA-SCL-674) lack forearm bones. Twelve of these otherwise well-articulated primary interments have distal humeri bearing cutmarks with a distribution like that seen in fur seals butchered by Native Californians. Most of the burials with missing forearms are young adult males, a demographic profile that differs significantly from the full sample. Three of these males show evidence of perimortem trauma in addition to forearm amputation. Drilled and polished human radii and ulnae were recovered from the CA-SCL-674 cemetery in archaeological contexts separate from burials with missing forearms. A warfare-related trophy-taking practice is strongly suggested by these bioarchaeological data. Based on these data, it seems likely that 20% (N = 10) or more of the adult males (N = 59) in this population were victims of violence. Evidence of perimortem violence was much less common among women, with only about 2% (N = 2) of adult females (N = 86) subjected to trophy-taking. Examination of museum collections produced further evidence for perimortem forearm amputation among the Native American inhabitants of this area during the transition between the Early and Middle periods. The emergence of more hierarchical social systems during this period may have fostered warfare-related trophy-taking as a symbolic tool for enhancing the power and prestige of individuals within competing social groups.