A little history: Galton and Individual Differences

Galton (1822-1911) believed based on Darwin's theory of evolution, that individual differences in intelligence are for the most part due to heredity. Galton wrote a book that was called "heredity genius" (Fancher, 1996, p. 226). For this argument he had three newly arguments that should support this. The first he based on the normal distribution, family trees of intellectual individuals, and adoptive versus biological relatives.