Philosophy of Biology

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Genetic Analysis 255

hypotheses: To the extent that the morphologist’s or physiologist’s unit character
did not agree with those of Mendelian segregation units, the former were not
really “unit characters,” but rather complex characters. Mendelian segregation
became for Bateson a device to assess spurious morphological unit characteristics
[Schwartz, 1998; 2002]. Such was the case of the “compound character” of birds’
comb, which appeared in four “antagonistic” forms that were inherited according
to Mendel’s rule of two independently segregating unit-characters [Bateson, 1928].
Bateson suggested a resolution of the “outward” or zygotic morphological unit
character, “being represented in the gametes by more than one factor” [Hurst,
1906]. When Bateson encountered cases of two or more unit-characters in which
“the proportions do not accord with Mendel’s assumption of random segregation,”
he interpreted these along his 1891 Theory of Repetition of Parts, namely that
“reduplication or proliferation” of gametes may take place, and that “some factors
are distributed according to one of the duplicated series and other factors according
to the normal Mendelian system” [Bateson and Punnett, 1911].
A main concern for Bateson was to bolster the particulate theory of inheritance,
as opposed to Karl Pearson’s biometrician’s belief in natural selection operating
upon small continuous variations. His attempt to “Mendelize” was bound to come
to a head-on collision with that of the logical positivist and author of the influential
treatiseGrammar of Science. Karl Pearson was drawn to the problems of inher-
itance by Francis Galton’sNatural Inheritance[Provine, 1971]. The correlation
coefficient between parents and offspring became for Galton and his followers the
typical measure of the hereditary force. “A major epistemological characteristic
of this approach was its purely descriptive character... Karl Pearson’s treatment
of ancestral heredity was exemplary in this respect” [Gayon, 2000, 74-75]. Thus,
although Bateson confronted Pearson with the theory of heredity, or genetics, con-
cerning a disciplinewithinthe theory of evolution, Pearson’s confrontations with
Bateson may be reduced to a conflict on the grammar of science: Whereas Pear-
son developed statistical methods for the analysis of data on variation, presumably
without being committed to any hypothetical speculation, Bateson’s starting point
was the hypothesis of particulate inheritance, or genetics.
In reality Pearson developed Galton’s “stirp” theory of inheritance, according to
which the traits of the individuals in one generation are the sum of the contribution
of those of their ancestors, one half of each parent, a quarter of each grandparent,
an eighth of each grand-grandparent, etc. On Mendel’s hypothesis ancestors were
helpful only to analyze the particulate status of an individual so as to allow the
prediction of the offspring’s properties of hybridization in generations to follow. As
shown by Udny G. Yule already in 1902, analytically the two approaches converge,
as long as one discernedheredityfromhybridization [Yule, 1902]: Mendelism is
concerned with hybridizations; Hybridization is the method to study thehereditary
variation of specific characteristics betweenindividuals. Heredity deals with the
population-aspect of inheritance (Tabery [2004]; see also Section 7, below).
Early Mendelians’ notions of theFaktorenwere basically preformationist: They
did not distinguish between theFaktor and the character proper. The parti-

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