Introduction

Abstract

‘Any theory of evolution must be based on the properties of Mendelian factors, and beyond this, must be concerned largely with the statistical situation in the species’; thus wrote Wright (1931) in the introduction to his famous paper ‘Evolution in Mendelian populations’. Similar statements can be found in the writings of Fisher (e.g. Fisher 1921) and Haldane (e.g. Haldane 1924a). The attempt, by these three workers, to analyse the evolutionary process quantitatively proved a brilliant success and provided an intellectual standard by which all subsequent discussions of evolution are judged. Their findings, which were accepted remarkably rapidly by almost all biologists, had a profound effect on evolutionary thinking. Most important was the discovery that natural selection, even of very modest intensity, will have a critical effect on both the direction and speed of the evolutionary process, particularly in large populations. It remained to be demonstrated whether, in natural populations, the intensity of selection at most loci would in fact be sufficiently large for the effects of natural selection to overwhelm those of other factors under most circumstances. Although initially there was much controversy on this question, observations on natural populations by ecological geneticists, led by Dobzhansky in the USA and by Ford in England, appeared to settle the matter.

May the Deluder of Intelligences never trouble the profundity of thine apprehension.

J. B. S. Haldane, My Friend Mr Leakey