Secular change and allometry in the long limb bones of Americans from the mid 1700s through the 1970

Secular change has long been of interest to researchers in fields ranging from human growth to human identification. In addition to changes in size, changes in limb bone proportions may also have occurred.;Secular change in size and limb bone length proportion was investigated in five U.S. skeletal samples (Total N = 2700) with dates of birth ranging from mid 1700 to 1970s. The six long bones are measured for maximum lengths, and stature is known for a approximately 2000 individuals. The goals of this study include (1) examining any changes in the long bones and stature of white and black males and females, and (2) examining the allometric relationships of the six long bones for these sex/race groups across time, and (3) examining any geographical differences in size and shape in a subsample.;In order to test for secular change in stature and bone lengths, regression is employed with each of the variables regressed onto year of birth. The second analysis involves the examination of allometric secular change. Size (geometric mean) and shape (X/size) were employed in a principal components analysis. The principal components of shape were then regressed onto year of birth for each sex/race group. Using Trotter's WWII sample, geographic differences are examined by using size and shape in principal components analysis and multivariate analysis of variance.;Results indicate that white males exhibit secular change in stature, all long bones, and most of their proportional relationships. Black males exhibit change in stature and all long bones except the humerus. White females show the same secular change in size and bone lengths as black males, while black females only exhibit change in stature. Results of the geographical analysis indicate that white males vary significantly by region in both size and shape, but black males do not.;Environmental improvements in the U.S. have lead to secular increases in size and bone lengths. Males exhibit a greater plastic response to these environmental changes, whereas females are more stable. Whites exhibit greater response than do blacks possibly due to harsher environmental conditions endured by blacks historically.