Secular Trends in Stature in an Historic Sioux Population

This study attempts to explore the possibility of the occurrence of secular trends in height in an historic population of Sioux American Indians, and presents the results from an analysis on anthropometric data from two primary sources. One data set was collected in the late 19th century under the direction of Franz Boas. A later early 20th century set was collected by Dr. James R. Walker. A cross sectional design is used to examine an unusually long span of Sioux history; ca. 1820-1880 for the adult (individuals over 20 yrs.) analysis, and ca. 1892-1907 for the children (aged 6 to 11 years). Trends observed in the data are interpreted in light of the insights they provide into the health and nutritional status of this population.

Adult heights (n=1195 tot.) were adjusted for aging effects and regressed on age, sexes being analyzed separately. Tests for differences between the means of age cohorts by decade of birth (1820-1880) were also carried out. The one sample of adults that showed significant differences between age-cohorts in this latter test also showed a significant positive linear secular trend (Walker's adult males). Child heights (n=717 tot.) were used to examine any trend within the 15 yr. interval between original observations (1892 and 1907). A test for equivalence of regression slopes and for means was carried out comparing the two samples of children.

No convincing secular trend could be discerned in the majority of the adult analysis (p < .05). Similarly the null hypothesis of equivalence of slopes could not be rejected in the analysis of the child samples. The failure to find any negative secular trend in this population of American Indians is remarkable given the drastic socioeconomic changes that occurred with the coming of the reservation period (1876 on), and the concomitant radical changes in subsistence lifeways. Comparisons with contemporary populations of White Americans also show that the Sioux remained consistently taller than Whites well into the reservation period.