76 Sahotra Sarkar
avid Darwinians — the mutationists were by no means dominant. Moreover, dur-
ing Mayr’s “classical period”, much of what population genetics had achieved was
exactly what Mayr had attributed to the “newer population genetics”. Contrary
to Mayr’s accusation of oversimplification, work in mathematical population ge-
netics in the late 1920s and 1930s had incorporated allelic interactions (degrees
of dominance), epistasis, frequency-dependent selection, and other factors. Most
importantly, Wright correctly insisted that he had emphasized gene interactions
throughout his life and that his parameter for selective value (or fitness) had
“always been defined as applying to atotal genotype in the system under con-
sideration, thus involving whatever interaction effects there may be among the
component genes” [Wright, 1960, 369].
Nevertheless, in 1963, Mayr republished his criticisms inAnimal Species and
Evolution. In a chapter entitled “The Unity of the Genotype”, he claimed:
The procedure of classical Mendelian genetics, of studying each gene
locus separately and independently, was a simplification necessary to
permit the determination of the laws of inheritance and to obtain basic
information on the physiology of the gene. When dealing with several
genes, the geneticist was inclined to think in terms of their relative
frequencies in the population. The Mendelian was apt to compare the
genetic composition of a population to a bag of colored beans. Mu-
tation was the exchange of one kind of one kind of bean for another.
This conceptualization has been referred to as ‘beanbag genetics.’...
Work in population and developmental genetics has shown, however,
that the thinking of beanbag genetics is in many ways quite mislead-
ing. To consider genes as independent units is meaningless from the
physiological as well as the evolutionary viewpoint. Genes not onlyact... but alsointeract. (p. 263)
Mayr ignored Wright’s response altogether.
Meanwhile, Haldane had briefly commented on Waddington’s criticism in 1953.
Writing the Foreword for the proceedings of the Oxford symposium at which
Waddington had first stated his criticisms, Haldane commented:
I shall first take advantage of having the last word by defending myself,
in my capacity as mathematical geneticist, against Waddington’s crit-
icism that ‘very few qualitatively new ideas have emerged from it’. I
think that some of them have emerged so completely that their origin
is forgotten. Darwin apparently [thought] that variation could only
[arise] by the effects of environmental differences in each generation.
Fisher first showed clearly that in large populations it diminished with
extreme slowness apart from the effects of natural selection, and Hage-
doorn that it would diminish at a measurable rate in small populations.
Wright then produced the qualitatively new idea of ‘drift’ or random
evolution in small populations.... Penrose and Haldane first showed