Species

Prologue xxxi

Ernst Mayr is someone whose ideas and narratives have been extremely inu-
ential, and therefore with whom we will deal later in some detail. He has often put
forward a narrative history of species concepts, and his ideas are the most widely
known and accepted. According to him, the species concept begins in biology with
Linnaeus,^29 because before then, apart from Ray, nobody believed species were sta-
ble entities. Later Darwin held that species were uid,^30 but in the intervening period
there was a tendency of various writers like Cuvier, De Candolle, Godron,^31 and von
Baer to treat them as real and denite entities, united, as von Baer says, by common
descent from original stock. The realization that species exhibited a “supraindividu-
alistic bond”^32 and that members of species reproduce only with each other came
slowly. The older view was “typological” and it is “the simplest and most widely
held species concept.”^33 Typology, according to Mayr, as for Simpson, is due to the
inuence of Plato, and those who follow him are trying to dene a species in terms
of “typical” or “essential” attributes:

Typological thinking nds it easy to reconcile the observed variability of the individu-

als of a species with the dogma of the constancy of species because the variability

does not affect the essence of the eidos [the Greek term translated as “species”] which

is absolute and constant. Since the eidos is an abstraction derived from human sense

impressions, and a product of the human mind, according to this school, its members

feel justied in regarding a species “a gment of the imagination,” an idea.^34

In contrast, he says, a species today is regarded as a gene pool rather than a class

of objects.

Mayr presents this history in more detail in his The Growth of Biological Thought.^35

Here again, the distal source of essentialism is Plato, now via Aristotle, to John Ray

and Linnaeus. Again, it is only with the increasing emphasis on empiricism and the

development rst of evolution and then of genetics that naturalists begin to realize

that species are gene pools, reproductively isolated from each other. In the end, the

biological species concept is triumphant.

A third history, for contrast, is that provided by David Hull, who became the lead-

ing philosopher of biology of his generation. He made it a point to focus on the actual

history and biology of his subjects rather than on a “rational reconstruction” or text-

book history, as was sometimes the practice of prior philosophical scholarship of sci-

ence. In his seminal paper “The effect of essentialism on taxonomy – two thousand

(^29) Mayr 1957, 2f.
(^30) Mayr 1957, 4.
(^31) Dominique-Alexandre Godron, a French botanist (1807–1880). According to Mayr [1982], his major
interest was in the nature of introduced species and the effects of cross-breeding [God ron 1854]. A
species xist, in his De l’espèce et des races dans les êtres organisés [ God ron 1859, 51] he wrote that
interbreeding in the wild, without human intervention, was sufcient to mark species, and that races
were only caused by such intervention.
(^32) Mayr 1957, 8.
(^33) Mayr 1957, 11.
(^34) Mayr 1957, 12.
(^35) Mayr 1982, 254 –279.