A Critique of Pure (Genetic) Information

28 Chapter 1
simplify further the explanation for this phenomenon, he proposed that
dominance and recessivity were really about the presence or absence of
some heritable Anlagen. In this way, the pure-breeding recessive line
simply lacked that heritable unit-character–allelomorph which shows up
as dominant in hybrids (heterozygotes) whose other parent comes from
a pure breeding line that possesses it. What this does not explain is why
a trait would fail to appear or appear in a highly attenuated form when
the allelomorph is present. To explain (away) such deviations from
Mendelian expectations without recourse to complicating the story by
reference to developmental interactions, the environment, and so forth,
the terms penetrance and expressivity, were introduced, which simply
turned phenotypic variability into intrinsic propensities of the
allelomorphs. 13
Johannsen’s Critique of the New Preformatonism—Origins of the
Phenotype-Genotype Distinction
The terms “gene,” “genotype” and “phenotype” were introduced by the
Danish botanist Wilhelm Johannsen, but his contribution to the advancement
of the gene concept ran far deeper than terminology. Keime and
Anlagen in nineteenth-century biology were concepts that pertained
first and foremost to development. Holistic and teleological when taken
together, they were not readily amenable to a reductive analysis. The
teleomechanist program refined its understanding of inheritance to the
extent that it established the continuity of the cell. The Kantian heuristic
required that the wherewithal for producing new forms be always
already contained within the potential of the germ. An explanation for
the appearance of new species (past or future) would thus be a further
extension of its theory of development, i.e., a new and more adaptively
specialized expression of the potential of the germ.
The question of transmission across generations only became an
important topic unto itself when the view arose that evolutionary
changes were based at least in part upon novel and possibly fortuitous
variations in the germ. Darwinian natural selection requires that progeny
of a species vary in what they contain in their egg, that is, in what is
transmitted from their parents. In attempting to formulate a way to con-