W F R Weldon first clearly formulated the principles of naturalselection in terms of what would have to be observed innatural populations in order to conclude that natural selectionwas, indeed, acting in the manner proposed by Darwin.The approach he took was the statistical method developedby Galton, although he was closer to Darwin’s conception ofselection acting on small individual variations than Galtonwas. Weldon, together with Karl Pearson, who supplied thestatistical innovations needed to infer the action of selectionfrom populational data on trait distributions, laid the foundationsof biometry and provided the first clear evidence of bothstabilizing and directional selection in natural populations.