In the second half of the nineteenth century, as Darwinism was making its impact upon biology, an interesting new approach to biological variation, especially intraspecific variation, was being examined. Instead of trying to describe variation patterns in words, the investigators, examining large samples of organisms, collected numerical data and subjected them to statistical analysis. In the following account we discuss selected themes: for comprehensive studies of the subject see Pearson & Kendall (1970), Kendall & Plackett (1977), Porter (1986) and Stigler (1986).

The first worker to study natural variation statistically, a science that became known as biometry, was probably the Belgian Quetelet (1796–1874). He wrote a famous series of letters on the subject to his pupil, the Grand Duke of Saxe-Coburg and Gotha. Later in the century, Darwin's cousin, Francis Galton (1822–1911), made notable contributions to the statistical investigation of variation and inheritance, ideas that were developed by many other investigators, especially in relation to social issues (see Bowler, 1989; Keynes, 1993; Gillham, 2001; Bulmer, 2003).

Biometrics and eugenics

While Darwin and others considered humankind to be a single species, others, for example the American biologist Louis Agassiz (1807–73), took the view that there were several species of humans. In the developing fields of anthropology and sociology, biometrical methods were increasingly employed to examine racial variation.

Darwinian concepts provoked many questions with social implications. In 1871, in his book The Descent of Man, Darwin wrote:

Darwin continues: