Enamel Rhythms Associate With Limited Body Size Variability In Beijing

Objectives: Our aim is to characterize variability of striae of Retzius RPs for a large sample of people of known body size from Beijing, China.
Methods: By light microscopy we evaluated 50-100 µm thick histological sections of orthodontic or carious tooth extractions. Each tooth was evaluated independently by at least 3 of the research participants; results are provided only for those teeth in which there was independent agreement.
Results: RP 6(N=3) 7(N=78) 8(N=41) 9(N=5) 10(N=0) 11(N=0) 12(N=0)

Of 188 individuals, 127 were reliably measured. RPs of the Beijing population sample exhibit a narrow range, 94% having RPs of only 7 or 8, consistent with a narrow range of heights (145-180cm). This is in marked contrast to the range of RPs observed for a sub Saharan African sample having a larger range of heights (110-190cm). A large body of evidence indicates that modern human biological diversity increases with time since geographic origin. Sub Saharan Africans have had more time than other regional human populations, including those of Asia, to generate variability in body size.
Conclusions:
The narrow range of RPs among a Beijing Chinese population sample may relate to limited variability of body size due to recency of geographic origin.