Bioarchaeological research of ancient Amerindians was undertaken to test the hypothesis that seronegative spondyloarthropathies (SNS) and diffuse idiopathic skeletal hyperostosis (DISH) existed in prehistoric South Americans. An osteological-radiographic model was developed from clinical literature and systematically applied to 504 archaeological human remains housed at the Universidad de Tarapacá in Arica, Chile, to search for evidence of these arthritides. The results showed that SNS existed with an average frequency of 7% for the adult sample and DISH averaged 4% in individuals over 40 years old. It was found that the antiquity of SNS date back at least 5,000 years in both New World and Old World populations. In contrast, the antiquity of DISH in the Americas is not clear because no previous studies have dealt with this subject; however, this research finds mild DISH cases dating back 4,000 years in northern Chile. It was also found that SNS and DISH exhibit a trend of increasing incidence with the advent of agro-pastoral activities and village formation.