"Had Mendel's work come into the hands of Darwin, it is not too much to
say that the history of the development of evolutionary philosophy would
have been very different from that which we have witnessed."[23]
[Footnote 23: William Bateson, "Mendel's Principles of Heredity," p.
316.]
I
From the latter part of the eighteenth century, attempts were
continually being made to explain the origin of all organic forms by
some system of development or evolution. Buffon had dwelt on the
modifications directly induced by the environment. Lamarck had made much
use of this idea, claiming that such modifications were transmitted to
posterity, and claiming the same for the structural changes produced by
use and disuse. Lamarck's work did not become at all popular while he
lived, chiefly through the overpowering influence of Baron Cuvier, who
had an equally fantastic scheme of his own, which may well be termed a
burlesque on Creation and in which an extreme fixity of "species" was a
cardinal doctrine. Erasmus Darwin and Robert Chambers in England also
tried to make a theory of evolution believable; though their efforts
were but little more successful in gaining the ear of the world.
But to all that had gone before Charles Darwin and A.R. Wallace (1858)
added the idea of "natural selection," or "the struggle for existence,"
to use the respective terms coined by each of these authors, as the
chief means by which the effects of variation are accumulated and
perpetuated so as to build up the modern complexities of the plant and
animal kingdoms. Partly because it was a psychological moment, from the
fact that the uniformitarian geology of Lyell with its graded advance of
existences from age to age seemed absolutely to demand some evolutionary
explanation; partly because artificial selection was a familiar idea of
proved value in selective breeding, and "natural selection" seemed an
exact parallel carried on by nature in the direction of continual
improvement; but perhaps more largely because the abstract idea of
"natural selection" involved so many intricate separate concepts that
for nearly a generation scarcely two naturalists in the world could
state the whole problem of the theory exactly alike;--on all these
accounts the theory of natural selection, or of the "survival of the
fittest," to use the phrase of Herbert Spencer, became in the latter
decades of the nineteenth century well-nigh universal.
But about 1887 a faction or school arose who criticized the main idea of
Darwin and Wallace and fell back on the Lamarckian factor of the
transmission of acquired characters as really the essential cause of
the process of evolution. Herbert Spencer, E.D. Cope and others did much
to criticize natural selection as inadequate to do what was attributed
to it, dwelling on the importance of the transmission of acquired
characters. Spencer even went so far as to declare, "either there has
been inheritance of acquired characters, or there has been no
evolution." These Neo-Lamarckians argued that natural selection alone
can neither explain the origin of varieties, nor the first steps in the
slow advance toward "usefulness." An organ must be already useful before
natural selection can take hold of it to improve it. Selection cannot
make a thing useful to start with, but only (possibly) make more useful
what already exists. Until the newly formed buds of developing limbs or
organs became decidedly "useful" to the individual or the species, would
they not be in the way, merely so many hindrances, to be removed by
natural selection instead of being preserved and improved? But, in this
view of the matter, they argued, what single organ of any species would
there be that must not thus have appeared long before it was wanted?
Or to use the pungent words quoted with approval by Hugo de Vries at the
end of his "Species and Varieties" (pp. 825, 826), "Natural selection
may explain the survival of the fittest, but it cannot explain the
arrival of the fittest."
This side of the argument is dwelt upon at some length by Alex. Graham
Bell, as reported in a recent interview. He says:
"Natural selection does not and cannot produce new species or varieties
or cause modifications of living organisms to come into existence. On
the contrary, its sole function is to prevent evolution. In its action
it is destructive merely,--not constructive,--causing death and
extinction, not life and progression. Death cannot produce life; and
though natural selection may produce the death of the unfit, it cannot
produce the fit, far less evolve the fittest. It may permit the fit to
survive by not killing them off, if they are already in existence; but
it does not bring them into being, or produce improvement in them after
they have once appeared."[24]
[Footnote 24: _World's Work_, December, 1913, p. 177.]
Opposing these Neo-Lamarckians were such prominent scientists as August
Weismann, A.R. Wallace, E. Ray Lankester, who strenuously opposed the
idea that "acquired characters," or more precisely _parental
experience_, are ever transmissible. In the subsequent years the
greatest variety of experimental tests have been applied to secure the
hereditary transmission of any sort of such acquired characters, with
uniformly negative results. One of the most elaborate of these
experiments was conducted by a German botanist, who transplanted 2,500
different kinds of mountain plants to the lowlands, where he studied
them for several years alongside their relatives, natives of these
lowlands. He found that their mountain environment had made absolutely
no permanent change in their structures or habits, which soon conformed
exactly with those of their relatives which had lived in the lowland
environment for centuries. Many similar efforts have been made to
confirm this doctrine of the transmission of acquired characters; but
their universal failure is like that of mechanics in trying to invent
perpetual motion.
Thomas Hunt Morgan sums up the present situation in the following words:
"To-day the theory has few followers among trained investigators, but it
still has a popular vogue that is wide-spread and vociferous." And we
may add that the extent of its spread is directly proportioned to the
need felt for this doctrine as a support of the theory of evolution,
while the vociferance of its advocates is inversely proportioned to the
evidence in its support.
As a result of extensive modern experiments and discussion, biologists
have grown very cautious, and are by no means so positive as they were
twenty years ago in affirming just _how_ species have come into
existence. Echoes of this old controversy between the two leading
schools of biologists are occasionally heard; but the enthusiasm with
which they set out a half century ago to solve the riddle of plant and
animal life has largely given way to a purpose to discard speculation
and patiently to observe and record actual facts. For with natural
selection discredited in the house of its friends, and Lamarckianism
under grave suspicion from want of a single well authenticated example,
it is hard to see what there is left of the biological doctrine that
has so dominated scientific thought for a half century. If each of these
opposed schools of scientists are right in _what they deny_, the whole
theoretical foundation for the origin of new kinds of animals and plants
is swept away,--absolutely gone. For if an individual really cannot
transmit what he has acquired in his lifetime, how can he transmit what
he has not got himself, and what none of his ancestors ever had? And if
natural selection cannot start a single organ of a single type, what is
the use of discussing its supposed ability to improve them after the
machinery is all built?