438 THE STRUCTURE OF EVOLUTIONARY THEORY
the causes of mutation might place evolutionary alteration under our control, and
give us power so far beyond the scope of selection that we might truly become the
masters of nature: "We may search for mutable plants in nature, or we may hope to
induce species to become mutable by artificial methods. The first promises to yield
results most quickly, but the scope of the second is much greater and it may yield
results of far more importance. Indeed, if it should once become possible to bring
plants to mutate at our will and perhaps even in arbitrarily chosen directions, there
is no limit to the power we may finally hope to gain over nature" (1905, p. 688).
On the second, and theoretical, issue of insights from evolutionary theory for
human cultural and racial differences, de Vries stated, with principled consistency,
that his views on the origin of species suggested no implications whatever: "Our
knowledge of the origin of species in nature has no bearing on social questions"
(1909a, volume 1, p. 156). De Vries regarded human racial distinctions as arising
entirely from selection (or drift) upon fluctuating variability. Homo sapiens
resides, with the vast majority of species, in a longstanding phase of stability; not,
like the evening primrose, in a rare state of mutability: "Since the beginning of the
diluvial period, man has not given rise to any new races or types. He is, in fact,
immutable, albeit highly variable" (1909a, volume 1, p. 156). This fluctuating
variation provides a source for all racial differences, which, however "profound" in
phenotypic appearance, must therefore remain as limited and changeable as any
alteration fashioned in this weak Darwinian mode:
Many mistakes may in the future be avoided if a clear distinction be drawn
between mutability and variability in the ordinary sense. The variability
exhibited by man is of the fluctuating kind: whereas species arise by
mutation. The two phenomena are fundamentally different. The assumption
that human variability bears any relation to the variation, which has or is
supposed to have caused the origin of species, is to my mind absolutely
unjustified. Man is a permanent type, like the vast majority of species of
animals and plants ... As we have seen, it is characteristic of these types to
exhibit a certain amount of fluctuating variability. Man is no exception to
this rule. Therefore all that we can apply to the treatment of social questions
is our knowledge of ordinary variability. The facts of specific
differentiation are interesting but not relevant (1909a, volume 1, pp. 154-
155).In sum, de Vries' Mutation Theory became the most important set of concepts
in evolutionary biology during the early 20th century. The theory attained this
central status by (1) its radically different and non-Darwinian view of the origin of
species; (2) the breadth of its concerns, ranging from variation at the smallest scale
to modes of geological pattern at the largest; (3) the range of its implications, as
illustrated above, thus expanding the doctrine from a scientific theory to a
comprehensive worldview.