248 THE STRUCTURE OF EVOLUTIONARY THEORY
by organismal selection alone founders on three bases, the first two negative in
logical barriers forced by the premise of organismal exclusivity, and the third
positive in a potential "rescue" sought by acknowledging a necessary role for
species selection: (1) He promotes a calculus of ultimate organismal success in
terms of number of descendant taxa, but cannot extend his argument for
diversification by selection of extreme variants to achieve the required perfect
transfer to the species level. (2) In order to explain trends, he backs himself into a
contradictory and ad hoc explanation for the elimination of ancestral forms by
natural selection in competition with descendants. (3) Faced with the logical
dilemma of runaway diversification under natural selection alone, he advocates
negative species selection based upon small population sizes to bring the process
of divergence into equilibrium.
Postscript: Solution to the Problem of the "Delicate Arrangement"
"DELICATE ARRANGEMENT"
The power of a new framework often becomes most apparent in its capacity to
solve small and persistent puzzles. I therefore end this section with a solution to an
old conundrum, and with another refutation for Brakeman’s (1980) claim that
Darwin pinched the principle of divergence from Wallace, and then lied to cover
up the theft. What did Wallace say about divergence? Did he really develop the
principle in useful ways that Darwin had not anticipated, and might have coveted
as his own? When we turn to Wallace's celebrated Ternate paper (sent to Darwin in
1858), we find only a cursory statement about divergence. Wallace only discusses
anagenetic trends of descendants away from ancestors. He does not even consider
the production of multiple taxa from single sources: "But this new, improved, and
populous race by itself, in course of time, gives rise to new varieties, exhibiting
several diverging modifications of form, any of which, tending to increase the
facilities for preserving existence, must, by the same general law, in their turn
become predominant. Here, then, we have progression and continued divergence
deduced from the general laws which regulate the existence of animals in a state of
Nature, and from the undisputed fact that varieties do frequently occur" (Wallace,
1858, in Barrett et al., 1987).
We must conclude that Wallace regarded a principle of divergence as "no big
deal." He grasped the idea in outline and apparently found no problem therein. His
short statement could not possibly have taught Darwin anything useful, for Darwin
had already carried the argument far beyond this basic comment. Why then did
Wallace fail to share Darwin's puzzlement, excitement and sense of complexity
about the principle of divergence? I can imagine two explanations. Either Wallace
simply didn't think the issue through to all the difficulties and implications that
Darwin recognized. (After all, malarial fits on Ternate are less conducive to deep
thought than years of protracted strolling around the sandwalk at Down.) Or he did
think the issue through and, finding nothing problematical, therefore devoted little
attention to the subject. If the second alternative is correct, then my framework for