In Chapter 3, Gould follows the influence of Morton’s work into the latter part of the 19th century. Although Charles Darwin’s theory of evolution challenged creationism, it also provided additional support for racist arguments of “mental and moral worth” (105). Both monogenists and polygenists found new ways to support theories of racially-inherited intellectual difference, and were now equipped with “standardized procedures and a developing body of statistical knowledge” to support their ideas (106).

Gould first introduces Darwin’s cousin, Francis Galton (1822-1911), a leader in popularizing the use of modern statistics, and who believed in measurement’s power to elucidate the “relative worth of peoples” (108). Gould then presents the case of Robert Bennett Bean (1874-1944), a Virginia physician who published extensive data on the corpus callosum, a flat bundle of fibers that connects the right and left hemispheres of the brain. Bean used his findings as the rationale for justifying unequal treatment of blacks, as he concluded that whites have “more brain up front in the seat of intelligence” (109). Bean’s data was challenged by his mentor, who found that not knowing the race of a brain until after measurement led to “no difference [in size] between whites and blacks” (112).