The Structure of Evolutionary Theory

(Michael S) #1

The Fruitful Facets of Gabon's Polyhedron 437



  1. "New elementary species attain their full constancy at once" (p. 562).
    Again, de Vries states his first words of explanation in a forthrightly and explicitly
    anti-Darwinian manner, in this case confuting gradualism and the adaptationist
    perspective. "Constancy is not the result of selection or of improvement. It is a
    quality of its own. It can neither be constrained by selection if it is absent from the
    beginning nor does it need any natural or artificial aid if it is present" (pp. 562-
    563).

  2. "Some of the new strains are evidently elementary species, while others
    are to be considered as varieties" (p. 564). De Vries regarded his taxonomy of
    relative merit and evolutionary potency of mutations (discussed on pp. 431-434) as
    sufficiently important to rank as one of the seven cardinal statements.

  3. "The same new species are produced in a large number of individuals" (p.
    566). De Vries also recognized the importance of his distinctive, non-genealogical
    principle (see p. 433) that mutations forming new "elementary species" may arise
    several times (thus imparting a greater chance of success to the novel taxon)%

  4. "The relation between mutability and fluctuating variability" (p. 568)— so
    stated as a phrase rather than a declarative sentence. De Vries recognized this
    causal claim for a fundamental distinction between two modes of variation as the
    focus of his theory (see pp. 430-432). No other point received so much discussion
    in his texts. I do not know why he placed this fundamental statement of his
    reductionist program in 6th position among 7 statements.

  5. "The mutations take place in nearly all directions" (p. 570—I shall present
    a more extensive discussion of this claim on pp. 446-451). De Vries emphasized
    this statement as his major tactic for maintaining fealty with Darwin at
    macroevolutionary scales, while destroying his mentor's theory for the origin of
    species. If the phenotypic ranges of new species form an isotropic distribution
    about the parental type, then the manifest directionality of evolution at geological
    scales must record the action of a higher selection process upon these species-level
    variations. Can a form of Darwinian argument therefore prevail among species (to
    produce trends), even while the sudden origin of new species precludes
    selectionism in Darwin's own favored realm?
    From this conceptual foundation, de Vries reached further to promote his
    mutation theory as the basis for an overarching worldview. To illustrate the range
    of implications explicitly developed by de Vries, consider just two issues of widely
    differing import. On the first, and practical, question of benefits to agriculture, the
    mutation theory suggested that conventional selection (on fluctuating variation)
    could only yield limited and easily reversed improvements. But new mutations
    might secure large and permanent benefits. Yet, as a practical dilemma, new
    mutations are rare and cannot be induced by our efforts. What benefit can emerge
    from scientific horticulture if this discipline must wait patiently for good fortune,
    and can then only apply the journeyman's procedure of preservation and
    propagation: "the practice of the horticulturist in producing new varieties is limited
    to isolation, whenever chance affords them" (1905, p. 606). As a legitimate escape
    from this disabling consequence of his theory, de Vries proposed that future
    knowledge of

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