Brief communication: A re-evaluation of the health index of southern Brazilian shellmound populations.

OBJECTIVES: The southern Brazilian shellmounds provide archaeological evidence of prolonged human activity in the coast from approximately 6000 to 1000 BP. Shellmound building populations exploited the rich coastal estuarine zones, and the human remains recovered from them are important sources of information on health and overall lifestyle of these mid-Holocene groups. Therefore, they were included in the Western Hemisphere Global History of Health project. The shellmounds contribute the highest Health Index in the Western Hemisphere, but these conclusions are based on collections that exclude postcranial remains. Here, we reconstruct the Health Index for one specific shellmound using both cranial and postcranial remains to determine whether the initial studies might misrepresent the relative health of the Brazilian shellmound builders. MATERIALS AND METHODS: The Health Index was calculated for a sample of 18 complete skeletons recovered from the shellmound Porto do Rio Vermelho 02 (Santa Catarina Island, Brazil). The Heath Index was calculated with and without postcranial markers and the results are compared with the Western Hemisphere Global History of Health data. RESULTS: The Health Index for Porto do Rio Vermelho 02 is lower than the reported average for American series in the Western Hemisphere Global History of Health Project and considerably lower than the original index reported for Brazilian shellmounds. This discrepancy is due to an increased prevalence of infectious disease and low stature. CONCLUSIONS: Although the Health Index remains a useful comparison statistic, re-evaluation of fragmentary skeletal remains demonstrates the need for caution when applying it to incomplete skeletal series.

Resource intensification and osteoarthritis patterns: changes in activity in the prehistoric Sacramento-San Joaquin Delta region.

OBJECTIVES: Ethnohistoric accounts and archaeological research from Central California document a shift from the use of lower-cost, high-ranked resources (e.g., large game) toward the greater use of higher-cost, low-ranked resources (e.g., acorns and small seeds) during the Late Holocene (4500-200 BP). The subsistence transition from higher consumption of large game toward an increased reliance on acorns was likely associated with increases in levels of logistical mobility and physical activity. This study predicts that mobility and overall workload patterns changed during this transition to accommodate new food procurement strategies and incorporate new dietary resources during the Late Holocene in Central California. MATERIALS AND METHODS: Osteoarthritis prevalence was scored in the shoulder, elbow, hip, and knee of adult individuals (n = 256) from seven archaeological sites in the Sacramento-San Joaquin Delta region. Comparisons were made between osteoarthritis prevalence, sex, age-at-death, and time period using ANCOVAs. RESULTS: The results of this study indicate significant increases in osteoarthritis prevalence in the hip of adult males and females during the Late Period (1200-200 BP), even after correcting for the cumulative effects of age. No differences were observed between the sexes or between time periods for the shoulder, elbow, and knee joints. DISCUSSION: The temporal increase in hip osteoarthritis supports the hypothesis that there was an increasing need for greater logistical mobility over time to procure key resources away from the village sites. Additionally, the lack of sex differences in osteoarthritis prevalence may suggest that females and males likely performed similar levels of activity during these periods.

Comparisons of statistical techniques to assess age-related skeletal markers in bioarchaeology.

OBJECTIVES: Many authors argue that inconsistencies between studies of skeletal markers are based on different data collection protocols, especially when comparing age-related markers such as osteoarthritis. Less attention is given to the choice of statistical techniques that are used to test the hypotheses associated with the data. This paper addresses how different statistical techniques compare the prevalence of age-related skeletal indicators, specifically osteoarthritis. MATERIALS AND METHODS: Osteoarthritis prevalence was scored in eight postcranial joints in 243 adult individuals from seven prehistoric archaeological sites in Central California, and data was compared between three time periods [Early (4800-2800 BP), Middle (2800-1200 BP), and Late (1200-250 BP)] using commonly used statistical tests: chi-square, Fisher's exact, and odds ratios. In addition, we analyzed the data with tests that are able to take into consideration the effect of age on osteoarthritis prevalence: ANCOVA and Factorial ANOVA. Finally, bootstraps were applied to the data to investigate how fluctuating frequencies, sample size, and age-at-death distributions affected the interpretations resulting from each test. RESULTS: The results demonstrate that the tests that consider age as a covariate (ANCOVA and Factorial ANOVA) are more efficient in rejecting the null hypothesis when smaller magnitudes of difference are observed between samples, irrespective of sample size, even though osteoarthritis prevalence fails to meet assumptions of normal distribution and homoscedasticity. DISCUSSION: ANCOVAs or Factorial ANOVAs that incorporate age as a covariate should be considered more often in studies that test different prevalences of age-related osteological markers among past populations.