1220 THE STRUCTURE OF EVOLUTIONARY THEORY
ultimate rejection by both camps. At age seventeen, he abandoned his Anglican
upbringing, became a Roman Catholic, and consequently (in a less tolerant age of
state religion) lost his opportunity for training in natural history at Oxford or
Cambridge. He became a lawyer but managed to carve out a distinguished career as
an anatomist nonetheless. He embraced evolution and won firm support from the
powerful T. H. Huxley, but his strongly expressed and idiosyncratic anti-Darwinian
views incurred the wrath of Britain's biological establishment. He tried to unite his
biology with his religion in a series of books and essays, and ended up
excommunicated for his trouble six weeks before his death.
The ever-perceptive Darwin had chosen well for his primary source of worry. In
this book, Mivart presents a thorough and logically inclusive account of structuralist
evolutionary thought as a substitute for natural selection (complete with the usual
linkage of channeling and saltation into a coherent primary critique). Mivart centered
his attack upon an argument embodied in a phrase that still persists as virtually his
only commonly recognized legacy to the history of evolutionary thought. He
introduces this phrase as the title to his first substantive chapter (after some opening
pages entitled "introduction"): "The incompetency of 'natural selection' to account for
the incipient stages of useful structures." (In my popular writing, I have referred to
this critique as the "5 percent of a wing principle," as expressed in the common
layman's objection: "I can understand how wings work for flight once they originate,
but how can evolution ever make a wing in Darwin's gradualist and adaptationist
mode if five percent of a wing can't possibly provide any benefit for flight?")
Mivart constructs this chapter as a compendium of examples where, in his
judgment, no putative value could be assigned to early incipient stages (lepidopteran
mimicry, flight, the placement of both eyes on the upper side of flatfishes, etc.). He
then concludes (1871, p. 61): "That minute, fortuitous, and indefinite variations could
have brought about such special forms and modifications as have been enumerated in
this chapter, seems to contradict not imagination, but reason."
Mivart then attempts to resolve this problem in the most obvious manner—by
the saltationist claim that intermediary stages never existed, and that novel
adaptations may arise in single steps. Interestingly, and as mentioned in Chapter 5 (p.
344), Mivart invokes the compelling structuralist model and image of Galton's
Polyhedron (see pp. 342-351) to illustrate this centerpiece of his system (pp. 97-98):
Arguments may yet be advanced in favor of the view that new species have
from time to time manifested themselves with suddenness, and by
modifications appearing at once (as great in degree as are those which
separate Hipparion from Equus), the species remaining stable in the intervals
of such modifications: by stable being meant that their variations only extend
for a certain degree in various directions, like oscillations in a stable
equilibrium. This is the conception of Mr. Galton, who compares