Chance in Evolution from Darwin to Contemporary Biology

Pence, Charles H. [UCL] Ramsey, Grant

This chapter summarizes a sequence of ways in which, from antiquity to the present, chance has been connected to, or in some cases dissociated from, two related concepts, contingency and randomness. Aristotle’s theory of generation steered a course between chance and necessity by affirming the contingency of reproductive chains without denying their reliability or their purposiveness. This fact supports recent scholarship debunking the idea that everyone before Darwin was a “typological essentialist.” Typological essentialism did exist, but only much later. It arose in the 17th and 18th century, when under the influence of modern physics necessity displaced contingency and chance was reduced to ignorance of deterministic causes. Darwin revived the contingency of reproductive lineages and the purposiveness of organic traits by innovatively inserting an element of chance between the origin of variation and its adaptive utility. His analysis has been amply confirmed by the discovery of random changes in DNA sequences. Randomness in this sense does not, however, make adaptation or evolution random. The subtle balance among chance, determinism, and purposiveness that is built into the idea of natural selection precludes that.