Cross-sectional growth and decline of human stature and brain weight in 19th-century Germany.

A new six-parameter two-phase nonlinear growth and decline model is fitted to cross-sectional data on human stature and brain weight obtained from autopsies in Germany at the end of the 19th century. Brain growth may have ended at a total age of approximately seven years, much younger than estimated in previous studies. Earlier statistical approaches may not have pinpointed the beginning of the plateau. The decline of stature was slight and is weakly significant. The decline of brain weight was stronger but occurred mostly after sixty years of age. Secular increase may have been unimportant from 1820 to 1900.