John Burdon Sanderson Haldane (1892 - 1964) had a wide range of interests in biology. He began by studying the respiratory system, using himself as an experimental subject. He then turned to biochemistry, and finally to genetics.
Here are some of his main contributions to evolutionary biology:
• He produced mathematical models of natural selection which allow gene frequencies to be predicted.
• He described a cost of natural selection, and investigated what limits this might place on the rate of evolution.
• He suggested that selection can maintain a polymorphism when the heterozygote is fitter than either homozygote (see heterozygotic advantage).
Haldane's work, together with that of R.A. Fisher and Sewall Wright, played a central part in the construction of the modern synthesis.
This photograph of J.B.S. Haldane was taken in 1914.