Evolution and Ethics and Other Essays

T >> Thomas H. Huxley >> Evolution and Ethics and Other Essays

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Geology makes huge demands upon time; and we regret to find that it has
exhausted ours--that what we meant for the briefest and most general
sketch of some geological considerations in favor of Darwins hypothesis
has so extended as to leave no room for considering "the great facts of
comparative anatomy and zoology" with which Darwins theory "very well
accords," nor for indicating how "it admirably serves for explaining
the unity of composition of all organisms, the existence of
representative and rudimentary organs, and the natural series which
genera and species compose." Suffice it to say that these are the real
strongholds of the new system on its theoretical side; that it goes far
toward explaining both the physiological and the structural gradations
and relations between the two kingdoms, and the arrangement of all
their forms in groups subordinate to groups, all within a few great
types; that it reads the riddle of abortive organs and of morphological
conformity, of which no other theory has ever offered a scientific
explanation, and supplies a ground for harmonizing the two fundamental
ideas which naturalists and philosophers conceive to have ruled the
organic world, though they could not reconcile them; namely, Adaptation
to Purpose and Conditions of Existence, and Unity of Type. To reconcile
these two undeniable principles is the capital problem in the
philosophy of natural history; and the hypothesis which consistently
does so thereby secures a great advantage.

We all know that the arm and hand of a monkey, the foreleg and foot of
a dog and of a horse, the wing of a bat, and the fin of a porpoise, are
fundamentally identical; that the long neck of the giraffe has the same
and no more bones than the short one of the elephant; that the eggs of
Surinam frogs hatch into tadpoles with as good tails for swimming as
any of their kindred, although as tadpoles they never enter the water;
that the Guinea-pig is furnished with incisor teeth which it never
uses, as it sheds them before birth; that embryos of mammals and birds
have branchial slits and arteries running in loops, in imitation or
reminiscence of the arrangement which is permanent in fishes; and that
thousands of animals and plants have rudimentary organs which, at least
in numerous cases, are wholly useless to their possessors, etc., etc.
Upon a derivative theory this morphological conformity is explained by
community of descent; and it has not been explained in any other way.

Naturalists are constantly speaking of "related species," of the
"affinity" of a genus or other group, and of "family
resemblance"--vaguely conscious that these terms of kinship are
something more than mere metaphors, but unaware of the grounds of their
aptness. Mr. Darwin assures them that they have been talking derivative
doctrine all their lives--as M. Jourdain talked prose--without knowing
it.

If it is difficult and in many cases practically impossible to fix the
limits of species, it is still more so to fix those of genera; and
those of tribes and families are still less susceptible of exact
natural circumscription. Intermediate forms occur, connecting one group
with another in a manner sadly perplexing to systematists, except to
those who have ceased to expect absolute limitations in Nature. All
this blending could hardly fail to suggest a former material connection
among allied forms, such as that which the hypothesis of derivation
demands.

Here it would not be amiss to consider the general principle of
gradation throughout organic Nature--a principle which answers in a
general way to the Law of Continuity in the inorganic world, or rather
is so analogous to it that both may fairly be expressed by the
Leibnitzian axiom, Natura non agit saltatim. As an axiom or
philosophical principle, used to test modal laws or hypotheses, this in
strictness belongs only to physics. In the investigation of Nature at
large, at least in the organic world, nobody would undertake to apply
this principle as a test of the validity of any theory or supposed law.
But naturalists of enlarged views will not fail to infer the principle
from the phenomena they investigate--to perceive that the rule holds,
under due qualifications and altered forms, throughout the realm of
Nature; although we do not suppose that Nature in the organic world
makes no distinct steps, but only short and serial steps--not
infinitely fine gradations, but no long leaps, or few of them.

To glance at a few illustrations out of many that present themselves.
It would be thought that the distinction between the two organic
kingdoms was broad and absolute. Plants and animals belong to two very
different categories, fulfill opposite offices and, as to the mass of
them are so unlike that the difficulty of the ordinary observer would
be to find points of comparison Without entering into details which
would fill an article, we may safely say that the difficulty with the
naturalist is all the other way--that all these broad differences
vanish one by one as we approach the lower confines of the two
kingdoms, and that no absolute distinction whatever is now known
between them. It is quite possible that the same organism may be both
vegetable and animal, or may be first the one and then the other. If
some organisms may be said to be at first vegetables and then animals,
others, like the spores and other reproductive bodies of many of the
lower Algae, may equally claim to have first a characteristically
animal, and then an unequivocally vegetable existence. Nor is the
gradation restricted to these simple organisms. It appears in general
functions, as in that of reproduction, which is reducible to the same
formula in both kingdoms, while it exhibits close approximations in the
lower forms; also in a common or similar ground of sensibility in the
lowest forms of both, a common faculty of effecting movements tending
to a determinate end, traces of which pervade the vegetable
kingdom--while, on the other hand, this indefinable principle, this
vegetable

"Animula vagula, blandula, Hospes comesque corporis,"

graduates into the higher sensitiveness of the lower class of animals.
Nor need we hesitate to recognize the fine gradations from simple
sensitiveness and volition to the higher instinctive and to the other
psychical manifestations of the higher brute animals. The gradation is
undoubted, however we may explain it.

Again, propagation is of one mode in the higher animals, of two in all
plants; but vegetative propagation, by budding or offshoots, extends
through the lower grades of animals. In both kingdoms there may be
separation of the offshoots, or indifference in this respect, or
continued and organic union with the parent stock; and this either with
essential independence of the offshoots, or with a subordination of
these to a common whole; or finally with such subordination and
amalgamation, along with specialization of function, that the same
parts, which in other cases can be regarded only as progeny, in these
become only members of an individual.

This leads to the question of individuality, a subject quite too large
and too recondite for present discussion. The conclusion of the whole
matter, however, is, that individuality--that very ground of being as
distinguished from thing--is not attained in Nature at one leap. If
anywhere truly exemplified in plants, it is only in the lowest and
simplest, where the being is a structural unit, a single cell,
member-less and organless, though organic--the same thing as those
cells of which all the more complex plants are built up, and with which
every plant and (structurally) every animal began its development. In
the ascending gradation of the vegetable kingdom individuality is, so
to say, striven after, but never attained; in the lower animals it is
striven after with greater though incomplete success; it is realized
only in animals of so high a rank that vegetative multiplication or
offshoots are out of the question, where all parts are strictly members
and nothing else, and all subordinated to a common nervous centre--is
fully realized only in a conscious person.

So, also, the broad distinction between reproduction by seeds or ova
and propagation by buds, though perfect in some of the lowest forms of
life, becomes evanescent in others; and even the most absolute law we
know in the physiology of genuine reproduction--that of sexual
cooperation--has its exceptions in both kingdoms in parthenogenesis, to
which in the vegetable kingdom a most curious and intimate series of
gradations leads. In plants, likewise, a long and finely graduated
series of transitions leads from bisexual to unisexual blossoms; and so
in various other respects. Everywhere we may perceive that Nature
secures her ends, and makes her distinctions on the whole manifest and
real but everywhere without abrupt breaks We need not wonder therefore
that gradations between species and varieties should occur; the more
so, since genera, tribes, and other groups into which the naturalist
collocates species, are far from being always absolutely limited in
Nature, though they are necessarily represented to be so in systems.
From the necessity of the case, the classifications of the naturalist
abruptly define where Nature more or less blends. Our systems are
nothing, if not definite. They express differences, and some of the
coarser gradations. But this evinces not their perfection, but their
imperfection. Even the best of them are to the system of Nature what
consecutive patches of the seven colors are to the rainbow.

Now the principle of gradation throughout organic Nature may, of
course, be interpreted upon other assumptions than those of Darwins
hypothesis--certainly upon quite other than those of a materialistic
philosophy, with which we ourselves have no sympathy. Still we conceive
it not only possible, but probable, that this gradation, as it has its
natural ground, may yet have its scientific explanation. In any case,
there is no need to deny that the general facts correspond well with an
hypothesis like Darwins, which is built upon fine gradations.

We have contemplated quite long enough the general presumptions in
favor of an hypothesis of the derivation of species. We cannot forget,
however, while for the moment we overlook, the formidable difficulties
which all hypotheses of this class have to encounter, and the serious
implications which they seem to involve. We feel, moreover, that
Darwins particular hypothesis is exposed to some special objections. It
requires no small strength of nerve steadily to conceive, not only of
the diversification, but of the formation of the organs of an animal
through cumulative variation and natural selection. Think of such an
organ as the eye, that most perfect of optical instruments, as so
produced in the lower animals and perfected in the higher! A friend of
ours, who accepts the new doctrine, confesses that for a long while a
cold chill came over him whenever he thought of the eye. He has at
length got over that stage of the complaint, and is now in the fever of
belief, perchance to be succeeded by the sweating stage, during which
sundry peccant humors may be eliminated from the system. For ourselves,
we dread the chill, and have some misgivings about the consequences of
the reaction. We find ourselves in the "singular position"
acknowledged by Pictet--that is, confronted with a theory which,
although it can really explain much, seems inadequate to the heavy task
it so boldly assumes, but which, nevertheless, appears better fitted
than any other that has been broached to explain, if it be possible to
explain, somewhat of the manner in which organized beings may have
arisen and succeeded each other. In this dilemma we might take
advantage of Mr. Darwins candid admission, that he by no means expects
to convince old and experienced people, whose minds are stocked with a
multitude of facts all regarded during a long course of years from the
old point of view. This is nearly our case. So, owning no call to a
larger faith than is expected of us, but not prepared to pronounce the
whole hypothesis untenable, under such construction as we should put
upon it, we naturally sought to attain a settled conviction through a
perusal of several proffered refutations of the theory. At least, this
course seemed to offer the readiest way of bringing to a head the
various objections to which the theory is exposed. On several accounts
some of these opposed reviews especially invite examination. We
propose, accordingly, to conclude our task with an article upon "Darwin
and his Reviewers."

III

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
observation 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 doctrines 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 quite 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, 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 mans mind rests long in a state neither of belief nor 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
Darwins 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
Darwins 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. Pictets article in the
Bibliotheque 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. Prof.
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 completely 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 fullness 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 criticise 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 thoroughgoing 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. Darwins
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;[III-8] 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.

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