Chapter XII

THE GROWTH OF WALLACE’S CONVICTIONS ON EVOLUTION AND DISCOVERY OF NATURAL SELECTION--BORNEO 1855--TERNATE 1858.

We have already seen in the earlier part of this volume, the gradual development of the theory of Natural Selection in the mind of Darwin, and the long succession of experiments and observations which he undertook before he could bring himself to publish anything upon the subject, as well as the conditions which forced him to a hurried publication in the end. It is of the deepest interest to compare with this the account which Wallace has given us of the mental process by which he arrived at the same conclusions.

This deeply interesting personal history has only been known during the last few years; in 1891 Wallace republished his “Essays on Natural Selection” in one volume, combined with “Tropical Nature,” and he has added (on pp. 20, 21) the following introductory note to Chapter II., viz. the reprint of his Linnean Society Memoir “On the Tendencies of Varieties to depart indefinitely from the Original Type.” The note is here reprinted in full:--

“As this chapter sets forth the main features of a theory
identical with that discovered by Mr. Darwin many years before
but not then published, and as it has thus an historical
interest, a few words of personal statement may be permissible.
After writing the preceding paper [“On the Law which has
Regulated the Introduction of New Species”] the question of
_how_ changes of species could have been brought about was
rarely out of my mind, but no satisfactory conclusion was
reached till February 1858. At that time I was suffering from
a rather severe attack of intermittent fever at Ternate in the
Moluccas, and one day, while lying on my bed during the cold
fit, wrapped in blankets, though the thermometer was at 88°
Fahr., the problem again presented itself to me, and something
led me to think of the ‘positive checks’ described by Malthus
in his ‘Essay on Population,’ a work I had read several years
before, and which had made a deep and permanent impression on my
mind. These checks--war, disease, famine and the like--must, it
occurred to me, act on animals as well as man. Then I thought of
the enormously rapid multiplication of animals, causing these
checks to be much more effective in them than in the case of
man; and while pondering vaguely on this fact there suddenly
flashed upon me the _idea_ of the survival of the fittest--that
the individuals removed by these checks must be on the whole
inferior to those that survived. In the two hours that elapsed
before my ague fit was over I had thought out almost the whole
of the theory, and the same evening I sketched the draft of my
paper, and in the two succeeding evenings wrote it out in full,
and sent it by the next post to Mr. Darwin. Up to this time
the only letters I had received from him were those printed in
the second volume of his _Life and Letters_ (vol. ii., pp. 95
and 108), in which he speaks of its being the twentieth year
since he ‘opened his first note-book on the question how and
what way do species and varieties differ from each other,’ and
after referring to oceanic islands, the means of distribution
of land-shells, &c., added: ‘My work, on which I have now been
at work more or less for twenty years, _will not fix or settle
anything_; but I hope it will aid by giving a large collection
of facts, with one definite end.’ The words I have italicised,
and the whole tone of his letters, led me to conclude that he
had arrived at no definite view as to the origin of species,
and I fully anticipated that my theory would be new to him,
because it seemed to me to settle a great deal. The immediate
result of my paper was that Darwin was induced at once to
prepare for publication his book on the _Origin of Species_ in
the condensed form in which it appeared, instead of waiting an
indefinite number of years to complete a work on a much larger
scale which he had partly written, but which in all probability
would not have carried conviction to so many persons in so short
a time. I feel much satisfaction in having thus aided in bringing
about the publication of this celebrated book, and with the
ample recognition by Darwin himself of my independent discovery
of ‘natural selection.’ (See _Origin of Species_, 6th ed.,
introduction, p. 1, and Life and Letters, vol. ii, chap. iv., pp.
115–129 and 145).”

[Sidenote: ORIGIN OF WALLACE’S ESSAY.]

A very similar account, differing in a few unimportant details from that quoted above, was written December 3rd, 1887, by Wallace to Professor Newton, and is published in the abridged “Life and Letters of Charles Darwin” (1892; pp. 189, 190). At the conclusion Wallace says:--

“... I _had_ the idea of working it out, so far as I was able,
when I returned home, not at all expecting that Darwin had so
long anticipated me. I can truly say _now_, as I said many years
ago, that I am glad it was so; for I have not the love of _work_,
_experiment_ and _detail_ that was so pre-eminent in Darwin, and
without which anything I could have written would never have
convinced the world.”

It is of great interest to learn that Wallace as well as Darwin was directed to natural selection by Malthus’ Essay. Hence, as the late Professor Milnes Marshall has pointed out (Lectures on the Darwinian Theory, pp. 212, 213), the laws of the multiplication and extinction of man suggested to both naturalists those more general laws by which it was possible to understand the development of the whole animal and vegetable worlds.

There is a tremendous contrast between these two discoverers, in the speed with which they respectively developed their ideas on the subject into a shape which satisfied them as suitable for publication. Wallace, after the inspiration which followed his reflections upon Malthus, had “thought out almost the whole of the theory” in two hours, and in three evenings had completed his essay. Darwin, receiving the same inspiration from the same source, in October 1838, wrote a brief account of it after four years’ reflection and work, and finished a longer account two years later, but was not prepared to give anything to the public until he was compelled to do so fourteen years later in 1858. All this delay was of the greatest advantage when a full exposition of the theory finally came before the world in the “Origin of Species”; for all difficulties had been fully considered and answered beforehand, while the wealth of new facts by which it was supported compelled a respectful hearing for the theory itself.

[Sidenote: WALLACE’S VIEWS.]

Wallace, like Darwin, was convinced of evolution before he discovered any principle which supplied a motive cause for the process. This conviction is expressed very clearly in his interesting essay already alluded to “On the Law which has regulated the Introduction of New Species” (Ann. and Mag., Nat. Hist., 1855, p. 184; reprinted without alteration in his Essays on Natural Selection). The law he states in these words:--

“Every species has come into existence coincident both in time
and space with a pre-existing closely allied species,”

a law which, as he justly claims for it,

“connects together and renders intelligible a vast number of
independent and hitherto unexplained facts. The natural system of
arrangement of organic beings, their geographical distribution,
their geological sequence, the phenomena of representative and
substituted groups in all their modifications, and the most
singular peculiarities of anatomical structure, are all explained
and illustrated by it, in perfect accordance with the vast mass
of facts which the researches of modern naturalists have brought
together, and, it is believed, not materially opposed to any of
them. It also claims a superiority over previous hypotheses, on
the ground that it not merely explains, but necessitates what
exists. Granted the law, and many of the most important facts in
Nature could not have been otherwise, but are almost as necessary
deductions from it, as are the elliptic orbits of the planets
from the law of gravitation.”

This important essay is dated by Wallace from Sarawak, Borneo, February, 1855.

The conclusions remind us of the words Darwin wrote in his note-book in 1837. “Led to comprehend true affinities. My theory would give zest to recent and Fossil comparative Anatomy.” By his theory Darwin here means evolution and not natural selection, which was not discovered by him until the end of 1838.