ABSTRACT
This chapter explores the power and importance of Lionel Sharpless Penrose's critique. It examines how his analysis of the relationship between intelligence and fertility helped contribute a more optimistic vision of man's biological future. Penrose's model enjoyed a mixed response from the biological community. In this, he was aided by evidence of an increase in the intellectual capacity of Western nations, as measured by a series of important post-war population surveys. The evidence provided by the Scottish Mental Survey of 1947 contradicted the eugenic assumptions of its creators and gave critical support to those who emphasized the decisive role of environmental factors in determining intellectual capacity. David Glass transformed the Scottish Mental Survey from a cross-sectional into a longitudinal survey, which measures the physical and intellectual growth of national samples of children. Francis Galton's arguments were applied to the study of children's growth by two leading figures of American physiology, Henry Pickering Bowditch and William Townsend Porter.
