The Revolution That Rewrote Life's History

Biologists have argued for a long time, long before molecular phylogenetics began complicating matters, about how to define species. The concept dates back at least to Carl Linnaeus, who during the 18th century defined a species in his system of binomial nomenclature as an entity (an aggregation of creatures, but still an entity) that had constancy and essence.

Charles Darwin in the 19th century, with help from Alfred Wallace and others, dismissed that sort of idealism, persuading people that species change, species originate and depart, species consist of individuals that vary from one another, sharing a certain degree of similarity but no ineradicable common essence.

In the 20th century, a clarified definition of was offered by Ernst Mayr, one of the founding neo-Darwinists. Mayr’s famous 1942 definition was: “Species are groups of actually or potentially interbreeding natural populations