182 Species“types,” and we should take him at his word that his theories had no effect upon his
classificatory activities.Moritz Wagner, Pierre Trémaux, and Geographic Speciation
Moritz Wagner (1813–1887) was a celebrated explorer and geographer, and his writ-
ings were influential. He had proposed, in opposition to Darwin’s notion that spe-
cies are formed from racial types through selection, that species must be isolated
geographically.^98 Mayr discusses the reaction of Darwin and his contemporaries to
Wagner’s isolation model.^99 Dismissed by Weismann and Wallace, as we shall see,
the geographical isolation thesis was nevertheless adopted by the Rev. J. T. Gulick,
whose work on Hawaiian landsnails (gen. Achatinella) led him also to claim that
much evolutionary variation was due to chance.^100 Thereafter, there seemed to be
two camps: those who thought that isolation was the sine qua non of speciation and
that chance was the cause of variation between populations, and those who thought
that speciation occurred equally if not entirely through the action of natural and
perhaps sexual selection. After the later work of Sewall Wright had been accepted
and promoted in the work of Dobzhansky during the mid-twentieth century, and fol-
lowing Poulton’s and Mayr’s coinages, this view came to be known as the allopatric
theory of speciation, and Darwin’s published view as the sympatric t he or y.
A possible unrecognized source for the notion of geographic isolation as a
mechanism for speciation is the work of the amateur anthropologist and architec-
ture scholar, Pierre Trémaux (1818–1895), whose work Origin et transformations
de l’homme et des autres étres (The origin and evolution of man and other beings),
published in 1865, proposed that the effects of local climate and conditions (sol)
would fully determine racial and species characters by adaptation, which would
then be maintained by interbreeding, or as he calls it, “crossing” (croisement).^101
Such changes would happen rapidly, evolutionarily speaking, and then reach an
equilibrium. Charitably interpreted, for the language of Origin et transformations
is florid and non-technical, Trémaux proposed both an allopatric theory and a punc-
tuated equilibrium theory. However, his amateur standing in the French scientific
community meant that his self-published works were not taken seriously, although
Darwin had two copies in his library, and had read at least one of them,^102 and as
a result may have revised his expression in the 1866 fourth edition of the Origin
of Species regarding the rates of change to include more or less rapid changes.^103
Trémaux has been unjustly tarred with being a crank because Marx wrote to Engels
to recommend him over Darwin and Engels replied that Trémaux was simply silly
and ignorant of the facts. Nearly every commentator since has relied on Engels’
(^98) Wag ner 1868, 1873, 1889.
(^99) Mayr 1982, 562–566.
(^100) Gulick 1873, 1888, 1890, 1908.
(^101) Trémaux 1865.
(^102) Wilkins and Nelson 2008.
(^103) Da r win 1866, 409f.