Annals of the History and Philosophy of Biology

150
Annals of the History and Philosophy of Biology, Vol. 10 (2005)
Nicolaas A. Rupke
In other words, Bronn postulated a spontaneous generation force that repeatedly
throughout geological history had produced the myriad of plant and animal species, in
the appropriate numbers for original survival, in their different locations, and in integral
connection with the changing environmental conditions of an evolving earth.
Already in his Handbuch einer Geschichte der Natur Bronn extensively addressed the issue
of the "Schöpfung der organischen Welt" and in particular the phenomenon of "Urzeugung."
If spontaneous generation of simple organisms took place at present, one
could reasonably infer that under special external conditions during earlier stages of earth
history also all other, higher species had spontaneously come into being. Bronn went
into considerable detail discussing pros and cons of the belief in spontaneous generation
today and admitted that such a belief did not appear supported by facts. Even so, in
order to explain the origin of new species one had to postulate the former existence of a
procreative capacity ("Zeugungs-Kraft") of abiogenesis that in more recent times had
expired. 8 In other words, he saw no alternative to autochthonous mega-generation.
Bronn returned to the question of this creative force ("Schöpfungs-Kraft") in his
Untersuchungen über die Entwickelungs-Gesetze der organischen Welt, reiterating that today no
species, not even primitive and simple ones, appear to originate spontaneously, but all
organic forms are produced by pre-existent living beings. The evidence against generatio
spontanea put forward by the microbiologist Christian Gottfried Ehrenberg and the
physiologist Theodor [Ambrose Hubert] Schwann appeared irrefutable. Yet although
there existed a certain organic variability that can lead to the origin of races, none of the
higher taxonomic entities – species, genus, let alone order or class – could have come
about by a process of transmutation from one into another, as assumed by Jean Baptiste
[Pierre Antoine de Monet] de Lamarck, Étienne Geoffroy St. Hilaire and Lorenz Oken. 9
Species were fixed. Historical geology showed no gradual transformation of old species
into new ones, "but the new ones have everywhere come into being without help of the
previous ones" ("sondern die neuen sind überall neu entstanden ohne Zuthun der vorigen"
(Bronn 1858, 80)).
Neither was divine creation an option. Science explained the physical world in terms
of natural laws, and it would be inconsistent not to do this in the case of the origin of
species and instead have recourse to supernatural intervention. Moreover, it would be
unbefitting the Deity to reduce Him to a common gardener by making Him carry out
innumerable little acts of planting life on earth. Thus there had been in operation in the
geological past an as yet unknown force of nature that by operating according to its own
laws had spontaneously brought forth from raw matter all plant and animal species,
8 "Läßt sich jene [Urerzeugung or Generatio spontanea] aber, wie es scheint, nicht erweisen, so müssen wir
gleichwohl die Urerzeugung, wenn auch als eine jetzt völlig erloschene Zeugungs-Kraft der Erde zu Hülfe
rufen, um die erste Entstehung der Arten zu erklären" (Bronn 1858, 30).
9 "Was die Umbildung der Thier- und Pflanzen-Formen in andere neue und vollkommenere betrifft, so
finden wir zwar, dass Varietäten einer Art eine gewisse Beständigkeit erlangen und zur 'Rasse' werden können,
welche aber auch wieder in die Urform zurückzukehren im Stande ist. Aber keine Erfahrung spricht
dafür, dass wirklich eine Art, eine Sippe oder sogar eine Ordnung und Klasse in eine andere übergehen
könne" (Bronn 1858, 79).