A Critical Examination of On The Origin of Species
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Thomas H. Huxley >> A Critical Examination of On The Origin of Species
But has this been done? or what is really the state of the case? It is
simply that, so far as we have gone yet with our breeding, we have not
produced from a common stock two breeds which are not more or less
fertile with one another.
I do not know that there is a single fact which would justify any one in
saying that any degree of sterility has been observed between breeds
absolutely known to have been produced by selective breeding from a
common stock. On the other hand, I do not know that there is a single
fact which can justify any one in asserting that such sterility cannot
be produced by proper experimentation. For my own part, I see every
reason to believe that it may, and will be so produced. For, as Mr.
Darwin has very properly urged, when we consider the phenomena of
sterility, we find they are most capricious; we do not know what it is
that the sterility depends on. There are some animals which will not
breed in captivity; whether it arises from the simple fact of their
being shut up and deprived of their liberty, or not, we do not know,
but they certainly will not breed. What an astounding thing this is, to
find one of the most important of all functions annihilated by mere
imprisonment!
So, again, there are cases known of animals which have been thought by
naturalists to be undoubted species, which have yielded perfectly
fertile hybrids; while there are other species which present what
everybody believes to be varieties* which are more or less infertile
with one another. There are other cases which are truly extraordinary;
there is one, for example, which has been carefully examined,--of two
kinds of sea-weed, of which the male element of the one, which we may
call A, fertilizes the female element of the other, B; while the male
element of B will not fertilize the female element of A; so that, while
the former experiment seems to show us that they are 'varieties', the
latter leads to the conviction that they are 'species'.
*[footnote] And as I conceive with very good reason; but if
any objector urges that we cannot prove that they have been
produced by artificial or natural selection, the objection
must be admitted--ultrasceptical as it is. But in science,
scepticism is a duty.
When we see how capricious and uncertain this sterility is, how unknown
the conditions on which it depends, I say that we have no right to
affirm that those conditions will not be better understood by and by,
and we have no ground for supposing that we may not be able to
experiment so as to obtain that crucial result which I mentioned just
now. So that though Mr. Darwin's hypothesis does not completely
extricate us from this difficulty at present, we have not the least
right to say it will not do so.
There is a wide gulf between the thing you cannot explain and the thing
that upsets you altogether. There is hardly any hypothesis in this
world which has not some fact in connection with it which has not been
explained, but that is a very different affair to a fact that entirely
opposes your hypothesis; in this case all you can say is, that your
hypothesis is in the same position as a good many others.
Now, as to the third test, that there are no other causes competent to
explain the phenomena, I explained to you that one should be able to
say of an hypothesis, that no other known causes than those supposed by
it are competent to give rise to the phenomena. Here, I think, Mr.
Darwin's view is pretty strong. I really believe that the alternative
is either Darwinism or nothing, for I do not know of any rational
conception or theory of the organic universe which has any scientific
position at all beside Mr. Darwin's. I do not know of any proposition
that has been put before us with the intention of explaining the
phenomena of organic nature, which has in its favour a thousandth part
of the evidence which may be adduced in favour of Mr. Darwin's views.
Whatever may be the objections to his views, certainly all others are
absolutely out of court.
Take the Lamarckian hypothesis, for example. Lamarck was a great
naturalist, and to a certain extent went the right way to work; he
argued from what was undoubtedly a true cause of some of the phenomena
of organic nature. He said it is a matter of experience that an animal
may be modified more or less in consequence of its desires and
consequent actions. Thus, if a man exercise himself as a blacksmith,
his arms will become strong and muscular; such organic modification is
a result of this particular action and exercise. Lamarck thought that
by a very simple supposition based on this truth he could explain the
origin of the various animal species: he said, for example, that the
short-legged birds which live on fish had been converted into the
long-legged waders by desiring to get the fish without wetting their
bodies, and so stretching their legs more and more through successive
generations. If Lamarck could have shown experimentally, that even
races of animals could be produced in this way, there might have been
some ground for his speculations. But he could show nothing of the
kind, and his hypothesis has pretty well dropped into oblivion, as it
deserved to do. I said in an earlier lecture that there are hypotheses
and hypotheses, and when people tell you that Mr. Darwin's
strongly-based hypothesis is nothing but a mere modification of
Lamarck's, you will know what to think of their capacity for forming a
judgment on this subject.
But you must recollect that when I say I think it is either Mr. Darwin's
hypothesis or nothing; that either we must take his view, or look upon
the whole of organic nature as an enigma, the meaning of which is
wholly hidden from us; you must understand that I mean that I accept it
provisionally, in exactly the same way as I accept any other hypothesis.
Men of science do not pledge themselves to creeds; they are bound by
articles of no sort; there is not a single belief that it is not a
bounden duty with them to hold with a light hand and to part with it
cheerfully, the moment it is really proved to be contrary to any fact,
great or small. And if, in course of time I see good reasons for such
a proceeding, I shall have no hesitation in coming before you, and
pointing out any change in my opinion without finding the slightest
occasion to blush for so doing. So I say that we accept this view as
we accept any other, so long as it will help us, and we feel bound to
retain it only so long as it will serve our great purpose--the
improvement of Man's estate and the widening of his knowledge. The
moment this, or any other conception, ceases to be useful for these
purposes, away with it to the four winds; we care not what becomes of
it!
But to say truth, although it has been my business to attend closely to
the controversies roused by the publication of Mr. Darwin's book, I
think that not one of the enormous mass of objections and obstacles
which have been raised is of any very great value, except that
sterility case which I brought before you just now. All the rest are
misunderstandings of some sort, arising either from prejudice, or want
of knowledge, or still more from want of patience and care in reading
the work.
For you must recollect that it is not a book to be read with as much
ease as its pleasant style may lead you to imagine. You spin through
it as if it were a novel the first time you read it, and think you know
all about it; the second time you read it you think you know rather
less about it; and the third time, you are amazed to find how little
you have really apprehended its vast scope and objects. I can
positively say that I never take it up without finding in it some new
view, or light, or suggestion that I have not noticed before. That is
the best characteristic of a thorough and profound book; and I believe
this feature of the 'Origin of Species' explains why so many persons
have ventured to pass judgment and criticisms upon it which are by no
means worth the paper they are written on.
Before concluding these lectures there is one point to which I must
advert,--though, as Mr. Darwin has said nothing about man in his book,
it concerns myself rather than him;--for I have strongly maintained on
sundry occasions that if Mr. Darwin's views are sound, they apply as
much to man as to the lower mammals, seeing that it is perfectly
demonstrable that the structural differences which separate man from
the apes are not greater than those which separate some apes from
others. There cannot be the slightest doubt in the world that the
argument which applies to the improvement of the horse from an earlier
stock, or of ape from ape, applies to the improvement of man from some
simpler and lower stock than man. There is not a single
faculty--functional or structural, moral, intellectual, or
instinctive,--there is no faculty whatever that is not capable of
improvement; there is no faculty whatsoever which does not depend upon
structure, and as structure tends to vary, it is capable of being
improved.
Well, I have taken a good deal of pains at various times to prove this,
and I have endeavoured to meet the objections of those who maintain,
that the structural differences between man and the lower animals are
of so vast a character and enormous extent, that even if Mr. Darwin's
views are correct, you cannot imagine this particular modification to
take place. It is, in fact, easy matter to prove that, so far as
structure is concerned, man differs to no greater extent from the
animals which are immediately below him than these do from other members
of the same order. Upon the other hand, there is no one who estimates
more highly than I do the dignity of human nature, and the width of the
gulf in intellectual and moral matters, which lies between man and the
whole of the lower creation.
But I find this very argument brought forward vehemently by some. "You
say that man has proceeded from a modification of some lower animal,
and you take pains to prove that the structural differences which are
said to exist in his brain do not exist at all, and you teach that all
functions, intellectual, moral, and others, are the expression or the
result, in the long run, of structures, and of the molecular forces
which they exert." It is quite true that I do so.
"Well, but," I am told at once, somewhat triumphantly, "you say in the
same breath that there is a great moral and intellectual chasm between
man and the lower animals. How is this possible when you declare that
moral and intellectual characteristics depend on structure, and yet
tell us that there is no such gulf between the structure of man and that
of the lower animals?"
I think that objection is based upon a misconception of the real
relations which exist between structure and function, between mechanism
and work. Function is the expression of molecular forces and
arrangements no doubt; but, does it follow from this, that variation in
function so depends upon variation in structure that the former is
always exactly proportioned to the latter? If there is no such
relation, if the variation in function which follows on a variation in
structure, may be enormously greater than the variation of the
structure, then, you see, the objection falls to the ground.
Take a couple of watches--made by the same maker, and as completely
alike as possible; set them upon the table, and the function of
each--which is its rate of going--will be performed in the same manner,
and you shall be able to distinguish no difference between them; but let
me take a pair of pincers, and if my hand is steady enough to do it,
let me just lightly crush together the bearings of the balance-wheel,
or force to a slightly different angle the teeth of the escapement of
one of them, and of course you know the immediate result will be that
the watch, so treated, from that moment will cease to go. But what
proportion is there between the structural alteration and the
functional result? Is it not perfectly obvious that the alteration is
of the minutest kind, yet that slight as it is, it has produced an
infinite difference in the performance of the functions of these two
instruments?
Well, now, apply that to the present question. What is it that
constitutes and makes man what he is? What is it but his power of
language--that language giving him the means of recording his
experience--making every generation somewhat wiser than its
predecessor,--more in accordance with the established order of the
universe?
What is it but this power of speech, of recording experience, which
enables men to be men--looking before and after and, in some dim sense,
understanding the working of this wondrous universe--and which
distinguishes man from the whole of the brute world? I say that this
functional difference is vast, unfathomable, and truly infinite in its
consequences; and I say at the same time, that it may depend upon
structural differences which shall be absolutely inappreciable to us
with our present means of investigation. What is this very speech that
we are talking about? I am speaking to you at this moment, but if you
were to alter, in the minutest degree, the proportion of the nervous
forces now active in the two nerves which supply the muscles of my
glottis, I should become suddenly dumb. The voice is produced only so
long as the vocal chords are parallel; and these are parallel only so
long as certain muscles contract with exact equality; and that again
depends on the equality of action of those two nerves I spoke of. So
that a change of the minutest kind in the structure of one of these
nerves, or in the structure of the part in which it originates, or of
the supply of blood to that part, or of one of the muscles to which it
is distributed, might render all of us dumb. But a race of dumb men,
deprived of all communication with those who could speak, would be
little indeed removed from the brutes. And the moral and intellectual
difference between them and ourselves would be practically infinite,
though the naturalist should not be able to find a single shadow of
even specific structural difference.
But let me dismiss this question now, and, in conclusion, let me say
that you may go away with it as my mature conviction, that Mr. Darwin's
work is the greatest contribution which has been made to biological
science since the publication of the 'Regne Animal' of Cuvier, and
since that of the 'History of Development' of Von Baer. I believe that
if you strip it of its theoretical part it still remains one of the
greatest encyclopaedias of biological doctrine that any one man ever
brought forth; and I believe that, if you take it as the embodiment of
an hypothesis, it is destined to be the guide of biological and
psychological speculation for the next three or four generations.