Seeds of Hierarchy 175
Lamarck's active centrality provides a foundation to my historical argument
because his theory, as presented in the next section, rests upon the concept of
hierarchy, with distinct causes at two primary levels. Lamarck's hierarchy differs
radically in form and logic from any acceptable modern version; indeed, I shall
reject the basis of Lamarck's notion as an important component in developing the
modern interpretation.
Lamarck's concept became Darwin's context. In perhaps the most widely
quoted of all his letters, Darwin wrote to Hooker on January 11, 1844 (in F.
Darwin, 1887, volume 2, p. 23): "I am almost convinced (quite contrary to opinion
I started with) that species are not (it is like confessing a murder) immutable.
Heaven forfend me from Lamarck nonsense of a 'tendency to progression,'
'adaptations from the slow willing of animals,' etc.! But the conclusions I am led to
are not widely different from his; though the means of change are wholly so. I
think I have found out (here's presumption!) the simple way by which species
become exquisitely adapted to various ends."
Hierarchy has resided at the heart of evolutionary theory from' the very
beginning, despite a temporary eclipse during the rally-round-the-flag period of
strict Darwinism at the middle of the 20th century. When the Beagle docked at
Montevideo, Darwin received his most precious item of mail— volume two of
Lyell`s Principles of Geology. His joy at this gift, and his careful study of the
contents, are well attested. This volume began with a long and careful exposition
of Lamarck's theory, fairly but negatively described by Lyell. Darwin formulated
his focal concept of small-scale change, based on organismal advantage as the
mechanism (by extrapolation) for all evolution, as an explicit denial of Lamarck's
hierarchy of causes. I believe that Darwin correctly rejected an untenable theory of
hierarchy based on distinct causes for different levels, but that (in a historically
portentous example of the cliche about babies and bathwater) he carried a good
thing too far by dismissing the general concept entirely. I conceived this book—
The Structure of Evolutionary Theory—both as a celebration of Darwin's
exemplary toughness, and as a call for the reinstitution of causal hierarchy,
properly reformulated.
LAMARCK'S TWO-FACTOR THEORY: SOURCES FOR THE
TWO PARTSIn the short period of 1797 to 1800, beginning with the Directory in power and
culminating in Napoleon's coup d'etat of 18th Brumaire year VIII (November
9,1799), Lamarck became an evolutionist and constructed the major features of his
theory. Scholars have identified many sources as Lamarck's primary impetus—his
developing views on spontaneous generation, his work on living and fossil shells
(Burkhardt, 1977), the implications of his unconventional theories in physics and
chemistry (Corsi, 1988). But I wish to present the logic, rather than the ontogeny,
of his final and completed argument.
Lamarck's evolutionary system attempts to marry two sets of ideas, each
embodying a primary module of his conceptual world. These two sets commingle
at their edges, but their distinction establishes the basis of Lamarckism,