1Anthropology, Texas State University-San Marcos, 2Anthropology, Texas State University-San Marcos, 3Anthropology, Texas State University
Saturday Afternoon, Forum Suite
Brain size is positively correlated with stature and body mass (Beals et al. 1984). Secular increases in stature and body mass have been detected in Americans over the past 150 years (Fogel 1994). Additionally, the length and height of the cranial vault has increased, while vault breadth has decreased (Jantz and Meadows Jantz 2000). These findings suggest a potential secular increase in brain size. Miller and Corsellis (1977) reported a positive secular trend for brain weight. The skeletal elements encasing the brain provide an opportunity to indirectly examine secular change in brain volume. Although bone thickness influences cranial vault dimensions, craniometric data may be reliably used to examine cranial volume (Henneberg 1988). Cranial module [(cranial length x cranial height x cranial breadth)1/3] measures the size of the cranial vault according to ectocranial dimensions. Our research investigated a potential increase in brain volume by examining the cranial modules of 749 American white males born between the 1830s and 1978. Crania were measured from the Robert J. Terry, Hamann-Todd, and William M. Bass Donated Collections, and from a collection of Civil War soldiers at the National Museum of Health and Medicine. Secular change was assessed by regressing cranial module on decade of birth. Mean cranial module values significantly (p<.05) increased from 150.75cm in the 1830s to 157.23cm in the 1970s. To the extent that ectocranial dimensions accurately reflect brain volume, the results of our research suggest an increase in the brain volumes of American white males over the past 150 years.