512 THE STRUCTURE OF EVOLUTIONARY THEORY
every important similarity!) Consider the first three exceptions listed by Fisher
(1930, p. 37):
- The systems considered in thermodynamics are permanent; species on the
contrary are liable to extinction, although biological improvement must be
expected to occur up to the end of their existence. - Fitness, although measured by a uniform method, is qualitatively different
for every different organism, whereas entropy, like temperature, is taken to have
the same meaning for all physical systems. - Fitness may be increased or decreased by changes in the environment,
without reacting quantitatively upon that environment.
But what do these exceptions express in ordinary biological parlance?
Contingency, individuality, and interaction, for the three points respectively. Could
anyone have presented a better list of the peculiarly biological properties that make
organisms and their history so intrinsically unlike simpler physical systems that
operate by timeless and general laws? Do these differences between physical
thermodynamics and Darwinian biology then rank as exceptions or invalidations?
THE EUGENICAL CHAPTERS. Fisher's Genetical Theory has generally been
acknowledged, and properly so, as the keystone of 20th century evolutionary
theory. Yet few contemporary biologists have actually read the book in extenso,
and one feature of this common neglect seems especially puzzling. The last five
chapters, nearly 40 percent of the entire volume, present a single coherent (if
fatally flawed) argument in eugenics—a claim that modern industrial society
(particularly the British version) has entered a potentially fatal decline as a result of
"social promotion of the relatively infertile." In essence, Fisher argues that people,
who rise socially, by dint of moral or intellectual superiority, also tend to express
ineluctable genetic propensities (not reversible, environmentally induced
preferences) for infertility. This superior upper stratum will therefore be swamped
by greater reproduction of less worthy social classes. Throughout human history,
most great civilizations have declined for this reason. Society should fight this
decay by rewarding gifted and highly fecund members of the lower classes, thereby
helping them to rise and rejuvenate the reproduction of higher social strata.
A tradition of discreet silence has enveloped these chapters. Provine (1971),
for example, relegates this material to a single sentence in his important book (pp.
153 - 154): "In the concluding five chapters he extended his genetical ideas to
human populations." This discretion, I suppose, reflects our embarrassment that
such a paragon of our profession should have ended his canonical book with such a
long argument for a politically discredited movement (see Gould, 1991c, for an
analysis and critique of Fisher's eugenical arguments). This professional silence
surely cannot reflect a belief that these chapters bear no connection to the rest of
the book, and that Fisher merely appended this material to grind his political axe—
for Fisher states that he could have dispersed this 40 percent among the other
chapters, and then adds