The origin of species, like all origination, like the institution of
any other natural state or order, is beyond our immediate ken. We see
or may learn how things go on; we can only frame hypotheses as to how
they began.
Two hypotheses divide the scientific world, very unequally, upon the
origin of the existing diversity of the plants and animals which
surround us. One assumes that the actual kinds are primordial; the
other, that they are derivative. One, that all kinds originated
supernaturally and directly as such, and have continued unchanged in
the order of Nature; the other, that the present kinds appeared in
some sort of genealogical connection with other and earlier kinds,
that they became what they now are in the course of time and in the
order of Nature.
Or, bringing in the word _species_, which is well defined as "the
perennial succession of individuals," commonly of very like
individuals,--as a close corporation of individuals perpetuated by
generation, instead of election,--and reducing the question to
mathematical simplicity of statement: species are lines of individuals
coming down from the past and running on to the future,--lines
receding, therefore, from our view in either direction. Within our
limited view they appear to be parallel lines, as a general thing
neither approaching to nor diverging from each other. The first
hypothesis assumes that they were parallel from the unknown beginning
and will be to the unknown end. The second hypothesis assumes that the
apparent parallelism is not real and complete, at least aboriginally,
but approximate or temporary; that we should find the lines convergent
in the past, if we could trace them far enough; that some of them, if
produced back, would fall into certain fragments of lines, which have
left traces in the past, lying not exactly in the same direction, and
these farther back into others to which they are equally unparallel.
It will also claim that the present lines, whether on the whole really
or only approximately parallel, sometimes fork or send off branches on
one side or the other, producing new lines, (varieties,) which run for
a while, and for aught we know indefinitely, when not interfered with,
near and approximately parallel to the parent line. This claim it can
establish; and it may also show that these close subsidiary lines may
branch or vary again, and that those branches or varieties which are
best adapted to the existing conditions may be continued, while others
stop or die out. And so we may have the basis of a real _theory_ of
the _diversification_ of species; and here, indeed, there is a real,
though a narrow, established ground to build upon. But, as systems of
organic Nature, both are equally _hypotheses_, are suppositions of
what there is no proof of from experience, assumed in order to account
for the observed phenomena, and supported by such indirect evidence as
can be had. Even when the upholders of the former and more popular
system mix up revelation with scientific discussion,--which we decline
to do,--they by no means thereby render their view other than
hypothetical. Agreeing that plants and animals were produced by
Omnipotent fiat does not exclude the idea of natural order and what we
call secondary causes. The record of the fiat--"Let the earth bring
forth grass, the herb yielding seed," etc., "and it was so"; "let the
earth bring forth the living creature after his kind, cattle and
creeping thing and beast of the earth after his kind, and it was
so"--seems even to imply them. Agreeing that they were formed of "the
dust of the ground" and of thin air only leads to the conclusion that
the pristine individuals were corporeally constituted like existing
individuals, produced through natural agencies. To agree that they
were created "after their kinds" determines nothing as to what were
the original kinds, nor in what mode, during what time, and in what
connections it pleased the Almighty to introduce the first individuals
of each sort upon the earth. Scientifically considered, the two
opposing doctrines are equally hypothetical.
The two views very unequally divide the scientific world; so that
believers in "the divine right of majorities" need not hesitate which
side to take, at least for the present. Up to a time within the memory
of a generation still on the stage, two hypotheses about the nature of
light very unequally divided the scientific world. But the small
minority has already prevailed: the emission theory has gone out; the
undulatory or wave theory, after some fluctuation, has reached high
tide, and is now the pervading, the fully established system. There
was an intervening time during which most physicists held their
opinions in suspense.
The adoption of the undulatory theory of light called for the
extension of the same theory to heat, electricity, and magnetism, and
this promptly suggested the hypothesis of a correlation, material
connection, and transmutability of heat, light, electricity,
magnetism, etc.; which hypothesis the physicists held in absolute
suspense until very lately, but are now generally adopting. If not
already established as a system, it promises soon to become so. At
least, it is generally received as a tenable and probably true
hypothesis.
Parallel to this, however less cogent the reasons, Darwin and others,
having shown it likely that some varieties of plants or animals have
diverged in time into cognate species, or into forms as different as
species, are led to infer that all species of a genus may have thus
diverged from a common stock, and thence to suppose a higher community
of origin in ages still farther back, and so on. Following the safe
example of the physicists, and acknowledging the fact of the
diversification of a once homogeneous species into varieties, we may
receive the theory of the evolution of these into species, even while
for the present we hold the hypothesis of a further evolution in cool
suspense or in grave suspicion. In respect to very many questions a
wise man's mind rests long in a state neither of belief nor of
unbelief. But your intellectually short-sighted people are apt to be
preternaturally clear-sighted, and to find their way very plain to
positive conclusions upon one side or the other of every mooted
question.
In fact, most people, and some philosophers, refuse to hold questions
in abeyance, however incompetent they may be to decide them. And,
curiously enough, the more difficult, recondite, and perplexing the
questions or hypotheses are, such, for instance, as those about
organic Nature, the more impatient they are of suspense. Sometimes,
and evidently in the present case, this impatience grows out of a fear
that a new hypothesis may endanger cherished and most important
beliefs. Impatience under such circumstances is not unnatural, though
perhaps needless, and, if so, unwise.
To us the present revival of the derivative hypothesis, in a more
winning shape than it ever before had, was not unexpected. We wonder
that any thoughtful observer of the course of investigation and of
speculation in science should not have foreseen it, and have learned
at length to take its inevitable coming patiently; the more so as in
Darwin's treatise it comes in a purely scientific form, addressed only
to scientific men. The notoriety and wide popular perusal of this
treatise appear to have astonished the author even more than the book
itself has astonished the reading world. Coming, as the new
presentation does, from a naturalist of acknowledged character and
ability, and marked by a conscientiousness and candor which have not
always been reciprocated, we have thought it simply right to set forth
the doctrine as fairly and as favorably as we could. There are plenty
to decry it, and the whole theory is widely exposed to attack. For the
arguments on the other side we may look to the numerous adverse
publications which Darwin's volume has already called out, and
especially to those reviews which propose directly to refute it.
Taking various lines and reflecting very diverse modes of thought,
these hostile critics may be expected to concentrate and enforce the
principal objections which can be brought to bear against the
derivative hypothesis in general, and Darwin's new exposition of it in
particular.
Upon the opposing side of the question we have read with attention, 1.
an article in the "North American Review" for April last; 2. one in
the "Christian Examiner," Boston, for May; 3. M. Pictet's article in
the "Bibliothèque Universelle," which we have already made
considerable use of, which seems throughout most able and correct, and
which in tone and fairness is admirably in contrast with, 4. the
article in the "Edinburgh Review" for May, attributed--although
against a large amount of internal presumptive evidence--to the most
distinguished British comparative anatomist; 5. an article in the
"North British Review" for May; 6. finally, Professor Agassiz has
afforded an early opportunity to peruse the criticisms he makes in the
forthcoming third volume of his great work by a publication of them in
advance in the "American Journal of Science" for July.
In our survey of the lively discussion which has been raised, it
matters little how our own particular opinions may incline. But we may
confess to an impression, thus far, that the doctrine of the permanent
and complete immutability of species has not been established, and may
fairly be doubted. We believe that species vary, and that "Natural
Selection" works; but we suspect that its operation, like every
analogous natural operation, may be limited by something else. Just as
every species by its natural rate of reproduction would soon fill any
country it could live in, but does not, being checked by some other
species or some other condition,--so it may be surmised that Variation
and Natural Selection have their Struggle and consequent Check, or are
limited by something inherent in the constitution of organic beings.
We are disposed to rank the derivative hypothesis in its fulness with
the nebular hypothesis, and to regard both as allowable, as not
unlikely to prove tenable in spite of some strong objections, but as
not therefore demonstrably true. Those, if any there be, who regard
the derivative hypothesis as satisfactorily proved must have loose
notions as to what proof is. Those who imagine it can be easily
refuted and cast aside must, we think, have imperfect or very
prejudiced conceptions of the facts concerned and of the questions at
issue.
We are not disposed nor prepared to take sides for or against the new
hypothesis, and so, perhaps, occupy a good position from which to
watch the discussion, and criticize those objections which are
seemingly inconclusive. On surveying the arguments urged by those who
have undertaken to demolish the theory, we have been most impressed
with a sense of their great inequality. Some strike us as excellent
and perhaps unanswerable; some, as incongruous with other views of the
same writers; others, when carried out, as incompatible with general
experience or general beliefs, and therefore as proving too much;
still others, as proving nothing at all: so that, on the whole, the
effect is rather confusing and disappointing. We certainly expected a
stronger adverse case than any which the thorough-going opposers of
Darwin appear to have made out. Wherefore, if it be found that the new
hypothesis has grown upon our favor as we proceeded, this must be
attributed not so much to the force of the arguments of the book
itself as to the want of force of several of those by which it has
been assailed. Darwin's arguments we might resist or adjourn; but some
of the refutations of it give us more concern than the book itself
did.
These remarks apply mainly to the philosophical and theological
objections which have been elaborately urged, almost exclusively by
the American reviewers. The "North British" reviewer, indeed, roundly
denounces the book as atheistical, but evidently deems the case too
clear for argument. The Edinburgh reviewer, on the contrary, scouts
all such objections,--as well he may, since he records his belief in
"a continuous creative operation," "a constantly operating secondary
creational law," through which species are successively produced; and
he emits faint, but not indistinct, glimmerings of a transmutation
theory of his own;[1] so that he is equally exposed to all the
philosophical objections advanced by Agassiz, and to most of those
urged by the other American critics, against Darwin himself.
Proposing now to criticize the critics, so far as to see what their
most general and comprehensive objections amount to, we must needs
begin with the American reviewers, and with their arguments adduced to
prove that a derivative hypothesis _ought not to be true_, or is not
possible, philosophical, or theistic.
It must not be forgotten that on former occasions very confident
judgments have been pronounced by very competent persons, which have
not been finally ratified. Of the two great minds of the seventeenth
century, Newton and Leibnitz, both profoundly religious as well as
philosophical, one produced the theory of gravitation, the other
objected to that theory that it was subversive of natural religion.
The nebular hypothesis--a natural consequence of the theory of
gravitation and of the subsequent progress of physical and
astronomical discovery--has been denounced as atheistical even down to
our own day. But it is now largely adopted by the most theistical
natural philosophers as a tenable and perhaps sufficient hypothesis,
and where not accepted is no longer objected to, so far as we know, on
philosophical or religious grounds.
The gist of the philosophical objections urged by the two Boston
reviewers against an hypothesis of the derivation of species--or at
least against Darwin's particular hypothesis--is, that it is
incompatible with the idea of any manifestation of design in the
universe, that it denies final causes. A serious objection this, and
one that demands very serious attention.
The proposition, that things and events in Nature were not designed to
be so, if logically carried out, is doubtless tantamount to atheism.
Yet most people believe that some were designed and others were not,
although they fall into a hopeless maze whenever they undertake to
define their position. So we should not like to stigmatize as
atheistically disposed a person who regards certain things and events
as being what they are through designed laws, (whatever that
expression means,) but as not themselves specially ordained, or who,
in another connection, believes in general, but not in particular
Providence. We could sadly puzzle him with questions; but in return he
might equally puzzle us. Then, to deny that anything was specially
designed to be what it is is one proposition; while to deny that the
Designer supernaturally or immediately made it so is another: though
the reviewers appear not to recognize the distinction.
Also, "scornfully to repudiate" or to "sneer at the idea of any
manifestation of design in the material universe"[2] is one thing;
while to consider, and perhaps to exaggerate, the difficulties which
attend the practical application of the doctrine of final causes to
certain instances is quite another thing: yet the Boston reviewers, we
regret to say, have not been duly regardful of the difference.
Whatever be thought of Darwin's doctrine, we are surprised that he
should be charged with scorning or sneering at the opinions of others,
upon such a subject. Perhaps Darwin's view is incompatible with final
causes;--we will consider that question presently;--but as to the
"Examiner's" charge, that he "sneers at the idea of any manifestation
of design in the material universe," though we are confident that no
misrepresentation was intended, we are equally confident that it is
not at all warranted by the two passages cited in support of it. Here
are the passages:--
"If green woodpeckers alone had existed, or we did not know that there
were many black and pied kinds, I dare say that we should have thought
that the green color was a beautiful adaptation to hide this
tree-frequenting bird from its enemies."
"If our reason leads us to admire with enthusiasm a multitude of
inimitable contrivances in Nature, this same reason tells us, though
we may easily err on both sides, that some contrivances are less
perfect. Can we consider the sting of the wasp or of the bee as
perfect, which, when used against many attacking animals, cannot be
withdrawn, owing to the backward serratures, and so inevitably causes
the death of the insect by tearing out its viscera?"
If the sneer here escapes ordinary vision in the detached extracts,
(one of them wanting the end of the sentence,) it is, if possible,
more imperceptible when read with the context. Moreover, this perusal
inclines us to think that the "Examiner" has misapprehended the
particular argument or object, as well as the spirit, of the author in
these passages. The whole reads more naturally as a caution against
the inconsiderate use of final causes in science, and an illustration
of some of the manifold errors and absurdities which their hasty
assumption is apt to involve,--considerations probably analogous to
those which induced Lord Bacon rather disrespectfully to style final
causes "sterile virgins." So, if any one, it is here Bacon that
"sitteth in the seat of the scornful." As to Darwin, in the section
from which the extracts were made, he is considering a subsidiary
question, and trying to obviate a particular difficulty, but, we
suppose, wholly unconscious of denying "any manifestation of design in
the material universe." He concludes the first sentence:--
----"and consequently that it was a character of importance, and
might have been acquired through natural selection; as it is, I
have no doubt that the color is due to some quite distinct cause,
probably to sexual selection."