Seeds of Hierarchy 213
tissues in an organism, and different species of birds in a broad geographical
region:
The case may be compared to that of a flock of nearly allied species of bird,
of which one species thrives best in the plains, another among the hills, and
a third among the mountain forests, all mingled together in a vast new
territory to which they had migrated, and in which all three kinds of
conditions were represented. A struggle would arise among the different
species, in which in every case the particular species would be victorious
which was best adapted to the local conditions ... This would be the result
of a struggle between the three species, not between individuals within each
species, and it could not therefore bring about an improvement of a single
species, but only the local prevalence of one or another (1904, volume 1,
pp. 248-249).Weismann's strong and valid critique of Roux leaves us with a puzzle: why
did Darwin, who understood the nature of selection so much better than anyone
else (see next section), become so intrigued with Roux's book, if Kampf der Theile
does not really develop a selectionist, or even a truly evolutionary, theory at all?
Several resolutions may be suggested. Most mundanely, Darwin was no German
scholar, and he may not, as he himself suggested to Romanes, have properly
understood the theory in his cursory reading. Secondly, Darwin was not a strict
selectionist, and may simply have valued Roux's insights on functional adaptation,
including the Lamarckian implications for a theory of heredity by extension. But,
in a third and intellectually more intriguing hypothesis, perhaps Darwin valued
Kampf der Theile for two genuine benefits or consonances that Roux's book
granted to natural selection—one practical, the other metaphorical.
In a practical sense, Roux explicitly provided the resolution of a paradox that
had plagued natural selection—the problem of too much adaptation ("organs of
extreme perfection" in Darwin's designation in Chapter 6 of the Origin). Can we
really believe that organismal selection constructs each barbule on every feather—
even with the immensity of geological time and the hecatomb of deaths in each
generation? Roux offered Darwin a sensible exit from such an untenable
implication: selection builds the capacity for an automatic functional response that
can directly shape each organism in minutely adaptive ways during growth:
"Through the capacity of the struggle of parts, a much higher perfection, the
purposefulness of the functioning part down to the last molecule, can arise, and
occur much more rapidly, than if it had to originate, by the Darwin-Wallace
principle, through selection of variation in the struggle for existence among
individuals" (Roux, 1881, p. 239).
But Roux offered even more, by way of metaphor, to Darwin's cardinal
vision—the paradox of higher stability arising through struggle among lower
elements. Functional adaptation might not rank as an evolutionary theory,
variants produced at a lower level—yet we rightly deem such a process creative in the
building of adaptations.