3 The New York Years (1931–1953)

University Student in Greifswald and Berlin 31
6. While the experimental biologist states that mutations are undirected (random),
the Lamarckian asserts mutations on the way to an adaptation are
directed 7 . It would make no sense to believe that the destabilization of the
germ plasm (caused by a mutation) would be without influence on subsequent
mutations–Orthogenesis.
7. Changed conditions of the environment influence the reaction of the body
plasma [soma] (modification of the phenotype). If this influence continues for
a lengthy period, the germ plasm will also be influenced, the modifications
become heritable, they become Dauermodifications, which after return to the
normal environment will disappear only after many generations (cumulative
aftereffect). We must assume such Dauermodifications in many geographical
races.
8. There are no proper arguments against Lamarck’s claim that organs deteriorate
by lack of use. It is in line with the economy of the organism that of the available
‘fund’ (Hesse) [resources] particularly those organs will be endowed which
are very much in use (Roux, the Struggle of Parts in the Organism). On the
other hand, it is reasonable that in the organs which are used most actively
corresponding to the degree of use, mutations will occur, the maintenance of
which will be controlled by selection.
9. The Lamarckian theory [in its modern version] is not teleological.”
Additional entries in his notebook read (transl.):
“Darwin distinguished between sudden and gradual changes too.”
“The genetico-darwinists always claim that a very small mutation is sufficient gradually
to prevail through natural selection. However, there are sufficient examples
that at least a predisposition for mutations is triggered by biological processes.”
“Certain doubts appeared whether everything can be explained by mutations
as, e.g., Baur hints at. These mutations have been derived from experiments. It is
questionable that this is a secure basis, because the conditions during experimental
work often are not normal, or better, not natural. There is another path, because
we encounter frequently natural experiments of speciation that originated under
natural conditions. An example is Stresemann’s ‘mutations’, […] and borderline
cases of the doctrine of Formenkreise.”
Mayr (1980n: 413) later stated, “I have no recollection of when I first learned
about evolution.” However, it is true that he had an early interest in evolution
and genetics if only coincidental to his enthusiasm for birds. Even though he
was inscribed as a medical student in Greifswald, he was first and foremost an
ornithologist.
Wide-ranging biological interests are documented by a notebook of 1925 with
hints to what Mayr considered open problems and topics suitable for possible
future research (transl.):
7 “I am here in agreement with Professor Buchner in Greifswald with whom I discussed
this point.”