"Evolutionist and missionary," The Reverend John Thomas Gulick (1832-1923). Part I: cumulative...

During the late 19th and early 20th centuries, the American missionary and naturalist John Thomas Gulick (1832-1923) was one of the most well-known and influential evolutionists, anticipating in his research and writing, later proposals of geographical isolation, population genetics, genetic drift, and the founder principle in speciation. In over 20 publications based on studies of non-adaptive geographical variation in several hundred species of snails in the genus Achatinella, collected in the valleys of Oahu in the Sandwich Islands (Hawaii), Gulick provided evidence for the formation of new species from varieties and the importance of geographical (non-adaptive) isolation in species diversification. Gulick's theory of the species-differentiating effects of isolation was regarded by many as a more complete theory of speciation than Darwin's, and by others as correcting a fundamental deficiency in Darwin's theory, namely how groups of organisms diversify one from another. Gulick also saw organisms as active participants in, and in interaction with, their environment, for which he coined the term coincident selection, anticipating the Baldwin effect/organic selection. With his concepts of cumulative segregation (geographical isolation), indiscriminate isolation (the Founder effect) and coincident selection (the Baldwin effect), we should recognize Gulick as one of the earliest and most original and innovative evolutionary biologists.