Seeds of Hierarchy 185
3 - 3. Lamarck allowed his linear sequence to branch at the apex of complexity (shown as the
bottom in this figure because he begins with the lowest forms and works down by descent).
Lamarck could not rank birds and mammals as part of the single sequence, and therefore allowed
a branch after reptiles with birds on one side (left, culminating in egg-laying monotremes), and
mammals to the right. From additional material added to the end of Volume 2 of the Philosophie
zoologique of 1809. (Author's collection.)caused by the environment, have given rise, on the one hand, to the formation of
birds, and, on the other hand, to the ... mammals."
I doubt that we can take this analysis much further. Historians often err in
trying to wrest consistency from great thinkers at all costs. Some issues are too
difficult, too encompassing, too important, too socially embedded, or just too
devoid of evidence, for resolution even by the finest scientists. Darwin never
consolidated his contradictory ideas about progess (see Chapter 6), and Lamarck
never found a thoroughly consistent way to fulfill his desired argument for a full
separation between two forces pulling evolution in orthogonal