3 The New York Years (1931–1953)

230 5 Biological Species and Speciation—Mayr’s First Synthesis
Brief History of the Biological Species Concept
The history of the biological species concept (BSC) goes back to the early 19th
century (Mayr 1955e, 1957f, 1959a, 1963b: 482–488, 1980f: 33, 1982d: 270–272; Grant
1994; Glaubrecht 2004; Haffer 1992, 2006). The first authors who used a biological
“shared essence” (fertility of matings) for a species definition were John Ray (1627–
1705) in 1686 and Georges Buffon (1707–1788) in 1749. However, their language
indicates that species, although real entities, are essentialistically constant and
invariable. Buffon’s species concept was widely adopted in Europe during the late
18th and early 19th centuries including Carl Illiger (1775–1813) in Germany whose
“Thoughts on the concepts species and genus in natural history” Mayr (1968i)
translated into English. He cited (1942e: 156; 1963b: 483) the amazingly perceptive
remarks on species and allopatric speciation by Leopold von Buch (1774–1853) in
1819 and 1825 about which Mayr may have learned from the articles by Robert
Mertens (1894–1975) in 1928 or several earlier authors who had also referred
to L. von Buch’s theory. This theory deeply influenced Charles Darwin who had
adopted a biological species concept in his notebooks during the 1830s, but later
gave it up. Major contributions to the formulation of the biological species concept
and the theory of allopatric speciation during the 19th century were then made by
H. W. Bates, A. R. Wallace, B. Walsh, H. Seebohm and later during the early 20th
century by Karl Jordan, Edward Poulton, Ludwig Plate, Erwin Stresemann and
B. Rensch (Fig. 5.7).
Dobzhansky (1935, 1937, 1940) discussed genetic differences between every discrete
group of individuals and the development of isolating mechanisms through
natural selection. He proposed the most useful term “isolating mechanism” between
species, but he included not only intrinsic but also extrinsic geographic
barriers which, of course, are something entirely different (Mayr 1942e). According
to Dobzhansky species may be conceived “statically” and “dynamically.” Statically,
“a species is a group of individuals fully fertile inter se, but barred from
interbreeding with other similar groups by its physiological properties (producing
either incompatibility of parents, or sterility of hybrids, or both)” or, in other
words, “discrete non-interbreeding groups of organisms” (1935: 353). His “dynamic
conception” of species was less satisfactory, because species are populations, not
stages in a process: “Dynamically, the species represents that stage of evolutionary
divergence, at which the once actually or potentially interbreeding array of forms
becomes segregated into two or more separate arrays which are physiologically
incapable of interbreeding” (1935: 354). Dobzhansky’s endorsement of the BSC
undoubtedly contributed to its increasing popularity.
Neither Dobzhansky nor any earlier Russian scientist were the originators of
the BSC, as Krementsov (1994) wrongly implied. He traced the roots of Dobzhansky’s
ideas backward to several Russian entomologists. While this is probably
correct, Krementsov (l. c.) conveyed the impression that these were the first to
develop the BSC. Some of his remarks read as follows: “The idea of biological
species attracted little attention in the west and was not much discussed” (p. 36),
“Western entomologists were generally less interested in discussing these ideas