Species

The Synthesis and Species 223

precu rsor itis”;^79 it is the importation of modern views into the past. At least since
Collingwood, such approaches to history as the progressive leading-up to the mod-
ern day or some ideal state have been widely viewed askance by historians:

Bach was not trying to write like Beethoven and failing; Athens was not a relatively

unsuccessful attempt to produce Rome; Plato was himself, not a half-developed

Aristotle^80

and, we might add, the writers on species in the period in question were not precur-

sors to Ernst Mayr.^81 There has always been a “biological” (reproductive) component

to discussions of species as applied to the living world, which I have called the “gen-

erative” notion of species. Moreover, few of the writers adduced by Mayr as forerun-

ners are actually presenting anything much like his view, as most of them include a

clear morphological component in their conceptions. Nevertheless, Mayr’s claim of

E. B. Poulton and K. Jordan as “precursors” would seem to be fair, at least in terms

of a similarity of views, and given the number of times he cites them, he may even

have them as direct antecedents—that is, they might have directly influenced him.

Stresemann, as his teacher, clearly did.^82

In his “point paper” on the biological species concept in the Wheeler and Meier

volume, Mayr repeats most of the previous paper. One thing he does add here is that

[t]he word interbreeding indicates a propensity; a spatially or chronologically isolated

population, of course, is not interbreeding with other populations but may have the

propensity to do so when the extrinsic isolation [is] terminated.^83

The shift in Mayr’s thinking from “actually or potentially interbreeding” in 1942,
to “actually or potentially operating isolating mechanisms” in 1963, to “propensity
to interbreed” in 2000 is interesting. As a test of species-status, potential anything is
obviously useless unless it can be made actual (which is the basis for his insistence
that only in sympatry are species fully determinable^84 ). But clearly one wants to
be able to say that I and the inhabitants of fifteenth-century England are the same
species, even if I cannot interbreed with them actually, and so Mayr must introduce
something like a propensity interpretation. However, “propensities to behave” are
themselves no easier on the metaphysical eye than potentialities. They remain, in the
end, conditional statements: a lump of sugar is soluble if, when immersed in water, it

(^79) Butterfield 1931; I am indebted to Neil Thomason for the phrase.
(^80) Collingwood 1946, 329.
(^81) Although this may sound harsh, Mayr has referred to his “precursors” as “prophetic spirits” [Mayr
1996, 269], noting “how tantalizingly close to a biological species concept some of the earlier authors
had come” [Mayr 1982, 271], and claimed that “Buffon understood the gist of it” and the early Darwin
also [Mayr 1997, 130], thus claiming authoritative precursors. Hull 1988, 372–377 and Winsor 2001
discuss the role precursors play in scientific histories. One function for precursors is to give legiti-
macy to the views of the modern scientist and deflect criticism to dead white males. Similar things
happened with Galileo, and also with the “rediscoverers” of Mendel.
(^82) Chung 2003, Winsor 2004.
(^83) Mayr 2000.
(^84) Mayr once told Hull in conversation that not potentially interbreeding was the equivalent of there
being isolating mechanisms present (Hull, pers. comm.).