A History of Science, vol 4 by Henry Smith Williams (best novels to read for beginners txt) đź“–
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It is true that here and there a scientist of greater or less
repute—as Von Buch, Meckel, and Von Baer in Germany, Bory
Saint-Vincent in France, Wells, Grant, and Matthew in England,
and Leidy in America—had expressed more or less tentative
dissent from the doctrine of special creation and immutability of
species, but their unaggressive suggestions, usually put forward
in obscure publications, and incidentally, were utterly
overlooked and ignored. And so, despite the scientific advances
along many lines at the middle of the century, the idea of the
transmutability of organic races had no such prominence, either
in scientific or unscientific circles, as it had acquired fifty
years before. Special creation held the day, seemingly unopposed.
DARWIN AND THE ORIGIN OF SPECIES
But even at this time the fancied security of the
special-creation hypothesis was by no means real. Though it
seemed so invincible, its real position was that of an apparently
impregnable fortress beneath which, all unbeknown to the
garrison, a powder-mine has been dug and lies ready for
explosion. For already there existed in the secluded work-room of
an English naturalist, a manuscript volume and a portfolio of
notes which might have sufficed, if given publicity, to shatter
the entire structure of the special-creation hypothesis. The
naturalist who, by dint of long and patient effort, had
constructed this powder-mine of facts was Charles Robert Darwin,
grandson of the author of Zoonomia.
As long ago as July 1, 1837, young Darwin, then twenty-eight
years of age, had opened a private journal, in which he purposed
to record all facts that came to him which seemed to have any
bearing on the moot point of the doctrine of transmutation of
species. Four or five years earlier, during the course of that
famous trip around the world with Admiral Fitzroy, as naturalist
to the Beagle, Darwin had made the personal observations which
first tended to shake his belief of the fixity of species. In
South America, in the Pampean formation, he had discovered “great
fossil animals covered with armor like that on the existing
armadillos,” and had been struck with this similarity of type
between ancient and existing faunas of the same region. He was
also greatly impressed by the manner in which closely related
species of animals were observed to replace one another as he
proceeded southward over the continent; and “by the
South-American character of most of the productions of the
Galapagos Archipelago, and more especially by the manner in which
they differ slightly on each island of the group, none of the
islands appearing to be very ancient in a geological sense.”
At first the full force of these observations did not strike him;
for, under sway of Lyell’s geological conceptions, he tentatively
explained the relative absence of life on one of the Galapagos
Islands by suggesting that perhaps no species had been created
since that island arose. But gradually it dawned upon him that
such facts as he had observed “could only be explained on the
supposition that species gradually become modified.” From then
on, as he afterwards asserted, the subject haunted him; hence the
journal of 1837.
It will thus be seen that the idea of the variability of species
came to Charles Darwin as an inference from personal observations
in the field, not as a thought borrowed from books. He had, of
course, read the works of his grandfather much earlier in life,
but the arguments of Zoonomia and The Temple of Nature had not
served in the least to weaken his acceptance of the current
belief in fixity of species. Nor had he been more impressed with
the doctrine of Lamarck, so closely similar to that of his
grandfather. Indeed, even after his South-American experience
had aroused him to a new point of view he was still unable to see
anything of value in these earlier attempts at an explanation of
the variation of species. In opening his journal, therefore, he
had no preconceived notion of upholding the views of these or any
other makers of hypotheses, nor at the time had he formulated any
hypothesis of his own. His mind was open and receptive; he was
eager only for facts which might lead him to an understanding of
a problem which seemed utterly obscure. It was something to feel
sure that species have varied; but how have such variations been
brought about?
It was not long before Darwin found a clew which he thought might
lead to the answer he sought. In casting about for facts he had
soon discovered that the most available field for observation lay
among domesticated animals, whose numerous variations within
specific lines are familiar to every one. Thus under
domestication creatures so tangibly different as a mastiff and a
terrier have sprung from a common stock. So have the Shetland
pony, the thoroughbred, and the draught-horse. In short, there is
no domesticated animal that has not developed varieties deviating
more or less widely from the parent stock. Now, how has this been
accomplished? Why, clearly, by the preservation, through
selective breeding, of seemingly accidental variations. Thus one
horseman, by constantly selecting animals that “chance” to have
the right build and stamina, finally develops a race of
running-horses; while another horseman, by selecting a different
series of progenitors, has developed a race of slow, heavy
draught animals.
So far, so good; the preservation of “accidental” variations
through selective breeding is plainly a means by which races may
be developed that are very different from their original parent
form. But this is under man’s supervision and direction. By what
process could such selection be brought about among creatures in
a state of nature? Here surely was a puzzle, and one that must be
solved before another step could be taken in this direction.
The key to the solution of this puzzle came into Darwin’s mind
through a chance reading of the famous essay on “Population”
which Thomas Robert Malthus had published almost half a century
before. This essay, expositing ideas by no means exclusively
original with Malthus, emphasizes the fact that organisms tend to
increase at a geometrical ratio through successive generations,
and hence would overpopulate the earth if not somehow kept in
check. Cogitating this thought, Darwin gained a new insight into
the processes of nature. He saw that in virtue of this tendency
of each race of beings to overpopulate the earth, the entire
organic world, animal and vegetable, must be in a state of
perpetual carnage and strife, individual against individual,
fighting for sustenance and life.
That idea fully imagined, it becomes plain that a selective
influence is all the time at work in nature, since only a few
individuals, relatively, of each generation can come to maturity,
and these few must, naturally, be those best fitted to battle
with the particular circumstances in the midst of which they are
placed. In other words, the individuals best adapted to their
surroundings will, on the average, be those that grow to maturity
and produce offspring. To these offspring will be transmitted the
favorable peculiarities. Thus these peculiarities will become
permanent, and nature will have accomplished precisely what the
human breeder is seen to accomplish. Grant that organisms in a
state of nature vary, however slightly, one from another (which
is indubitable), and that such variations will be transmitted by
a parent to its offspring (which no one then doubted); grant,
further, that there is incessant strife among the various
organisms, so that only a small proportion can come to
maturity—grant these things, said Darwin, and we have an
explanation of the preservation of variations which leads on to
the transmutation of species themselves.
This wonderful coign of vantage Darwin had reached by 1839. Here
was the full outline of his theory; here were the ideas which
afterwards came to be embalmed in familiar speech in the phrases
“spontaneous variation,” and the “survival of the fittest,”
through “natural selection.” After such a discovery any ordinary
man would at once have run through the streets of science, so to
speak, screaming “Eureka!” Not so Darwin. He placed the
manuscript outline of his theory in his portfolio, and went on
gathering facts bearing on his discovery. In 1844 he made an
abstract in a manuscript book of the mass of facts by that time
accumulated. He showed it to his friend Hooker, made careful
provision for its publication in the event of his sudden death,
then stored it away in his desk and went ahead with the gathering
of more data. This was the unexploded powder-mine to which I have
just referred.
Twelve years more elapsed—years during which the silent worker
gathered a prodigious mass of facts, answered a multitude of
objections that arose in his own mind, vastly fortified his
theory. All this time the toiler was an invalid, never knowing a
day free from illness and discomfort, obliged to husband his
strength, never able to work more than an hour and a half at a
stretch; yet he accomplished what would have been vast
achievements for half a dozen men of robust health. Two friends
among the eminent scientists of the day knew of his labors—Sir
Joseph Hooker, the botanist, and Sir Charles Lyell, the
geologist. Gradually Hooker had come to be more than half a
convert to Darwin’s views. Lyell was still sceptical, yet he
urged Darwin to publish his theory without further delay lest he
be forestalled. At last the patient worker decided to comply with
this advice, and in 1856 he set to work to make another and
fuller abstract of the mass of data he had gathered.
And then a strange thing happened. After Darwin had been at work
on his “abstract” about two years, but before he had published a
line of it, there came to him one day a paper in manuscript, sent
for his approval by a naturalist friend named Alfred Russel
Wallace, who had been for some time at work in the East India
Archipelago. He read the paper, and, to his amazement, found
that it contained an outline of the same theory of “natural
selection” which he himself had originated and for twenty years
had worked upon. Working independently, on opposite sides of the
globe, Darwin and Wallace had hit upon the same explanation of
the cause of transmutation of species. “Were Wallace’s paper an
abstract of my unpublished manuscript of 1844,” said Darwin, “it
could not better express my ideas.”
Here was a dilemma. To publish this paper with no word from
Darwin would give Wallace priority, and wrest from Darwin the
credit of a discovery which he had made years before his
codiscoverer entered the field. Yet, on the other hand, could
Darwin honorably do otherwise than publish his friend’s paper and
himself remain silent? It was a complication well calculated to
try a man’s soul. Darwin’s was equal to the test. Keenly alive
to the delicacy of the position, he placed the whole matter
before his friends Hooker and Lyell, and left the decision as to
a course of action absolutely to them. Needless to say, these
great men did the one thing which insured full justice to all
concerned. They counselled a joint publication, to include on the
one hand Wallace’s paper, and on the other an abstract of
Darwin’s ideas, in the exact form in which it had been outlined
by the author in a letter to Asa Gray in the previous year—an
abstract which was in Gray’s hands before Wallace’s paper was in
existence. This joint production, together with a full statement
of the facts of the case, was presented to the Linnaean Society
of London by Hooker and Lyell on the evening of July 1, 1858,
this being, by an odd coincidence, the twenty-first anniversary
of the day on which Darwin had opened his journal to collect
facts bearing on the “species question.” Not often
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