Racial variation in the sternal extremity of the rib and its effect on age determination.

Most research on the aging process in the skeleton has not considered or elaborated differences that may exist between the races. Thus, techniques developed for the estimation of age assume that the racial background of the standards is compatible with the specimens to be assessed. However, racial differences in areas such as skeletal growth and bone density have been reported, along with specific variations in the aging process, in the ribs of disparate populations. The present investigation examines metamorphosis in the sternal ribs of American blacks (N = 53 males, N = 20 females), and tests the application of age estimation standards developed by the authors from a white population. All specimens were obtained from medical examiner's cases of known age, sex, and race. Although the sample was limited in both quantity and age range, analysis of the data revealed racial differences in both rate and pattern of metamorphosis. Statistical analysis showed that the calculated mean age per phase for black ribs was nearly identical to whites in Phases 1 through 4 or until the mean age of 28 years. By the early 30s, differences in morphology and their chronological association with the aging process became apparent and increased with age in both sexes. Blacks were consistently overaged from 3 to 10 years in Phases 5 through 7. Therefore, it was concluded that biological differences between these populations do exist and can affect age estimation from the rib. Social factors may also be involved, but they cannot be demonstrated from the available data. While the degree of interracial variation does not require completely new standards, the authors have suggested specific modifications of the white standards for use on black specimens.