176 THE STRUCTURE OF EVOLUTIONARY THEORY
and provides a hierarchical context for this first comprehensive attempt to
formulate an evolutionary theory.
The first set: environment and adaptation
The first set focuses on adaptation, and links this key attribute of organisms to the
history of environments, the general pace of change, and the intimate relationship
between physical and biological worlds through time. (Corsi, 1988, grants primacy
to this set in the ontogeny of Lamarck's developing ideas; I accept this assertion
but note that the same set, curiously, becomes secondary in the logic of Lamarck's
fully formulated argument.) The framework can be entered in several places, with
the rest of the edifice following by implication from a few basic premises.
Lamarck's views on extinction provide a good beginning.
In opposition to his colleague Cuvier, and acting as a major source of their
estrangement, Lamarck denied that true extinction (defined as termination of
genealogical lines) could occur—though he allowed an exception for large
quadrupeds wiped out by human predation. (Cuvier, on the other hand, embraced
extinction both as the foundation of geological ordering, and as a cardinal
indication that animals cannot evolve to match changing environments.) Yet, as a
molluscan paleontologist, Lamarck knew that the morphologies of organisms
within major taxonomic groups changed in an orderly manner through time.
Evolution of outward form, with consequent preservation of lineages from
extinction, represents the only alternative to termination of lineages followed by
creation of new and different morphologies.
Lamarck far out-Lyelled Lyell in his commitment to uniformitarian geology
(an ironic fact, given Lyell's lambasting of Lamarckian biology in his own treatise
on geological uniformity). Lamarck's geological volume, the Hydrogeologie of
Year X (1802), may strike us as bizarre in several particular assertions; but his
general commitment to uniformity cannot be denied as a primary feature. Lamarck
would admit no causes not now observable in operation; in particular, no
paroxysms or catastrophes beyond the range of modern effects. He adopted
Hutton's rigidly ahistorical vision (see Gould, 1987b) and postulated a geological
history ruled by aqueous erosion (hence the title of his work). Cycles of
construction and erosion unfold so many times, and in so similar a manner, that
individual moments lose any distinctness, given past and future repetition of their
features. Ocean waters carve mountains and continents (though Lamarck made an
exception for volcanoes built by magmas). Currents tend to flow from east to west,
and continents therefore erode on their eastern borders and accrete by deposition at
their western edges. In a sense, therefore, continents undergo a slow westward
march around the globe. This curious circumnavigation has occurred several times
during the earth's extended history. But why doesn't the process yield directionality
as erosion wears continents down to flat plains permanently below water? Lamarck
countered with his distinctive mineralogical thesis: all rocks arise as ultimate
products of organic deposition. Erosion may break continents into tiny
comminuted grains, bits, and dissolved material; but as