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Darwiniana

T >> Thomas Henry Huxley >> Darwiniana




It is true that if philosophers have suffered, their cause has been amply
avenged. Extinguished theologians lie about the cradle of every science as
the strangled snakes beside that of Hercules; and history records that
whenever science and orthodoxy have been fairly opposed, the latter has
been forced to retire from the lists, bleeding and crushed if not
annihilated; scotched, if not slain. But orthodoxy is the Bourbon of the
world of thought. It learns not, neither can it forget; and though, at
present, bewildered and afraid to move, it is as willing as ever to insist
that the first chapter of Genesis contains the beginning and the end of
sound science; and to visit, with such petty thunderbolts as its
half-paralysed hands can hurl, those who refuse to degrade Nature to the
level of primitive Judaism.

Philosophers, on the other hand, have no such aggressive tendencies. With
eyes fixed on the noble goal to which "per aspera et ardua" they tend, they
may, now and then, be stirred to momentary wrath by the unnecessary
obstacles with which the ignorant, or the malicious, encumber, if they
cannot bar, the difficult path; but why should their souls be deeply vexed?
The majesty of Fact is on their side, and the elemental forces of Nature
are working for them. Not a star comes to the meridian at its calculated
time but testifies to the justice of their methods--their beliefs are "one
with the falling rain and with the growing corn." By doubt they are
established, and open inquiry is their bosom friend. Such men have no fear
of traditions however venerable, and no respect for them when they become
mischievous and obstructive; but they have better than mere antiquarian
business in hand, and if dogmas, which ought to be fossil but are not, are
not forced upon their notice, they are too happy to treat them as
non-existent.

* * * * *

The hypotheses respecting the origin of species which profess to stand upon
a scientific basis, and, as such, alone demand serious attention, are of
two kinds. The one, the "special creation" hypothesis, presumes every
species to have originated from one or more stocks, these not being the
result of the modification of any other form of living matter--or arising
by natural agencies--but being produced, as such, by a supernatural
creative act.

The other, the so-called "transmutation" hypothesis, considers that all
existing species are the result of the modification of pre-existing
species, and those of their predecessors, by agencies similar to those
which at the present day produce varieties and races, and therefore in an
altogether natural way; and it is a probable, though not a necessary
consequence of this hypothesis, that all living beings have arisen from a
single stock. With respect to the origin of this primitive stock, or
stocks, the doctrine of the origin of species is obviously not necessarily
concerned. The transmutation hypothesis, for example, is perfectly
consistent either with the conception of a special creation of the
primitive germ, or with the supposition of its having arisen, as a
modification of inorganic matter, by natural causes.

The doctrine of special creation owes its existence very largely to the
supposed necessity of making science accord with the Hebrew cosmogony; but
it is curious to observe that, as the doctrine is at present maintained by
men of science, it is as hopelessly inconsistent with the Hebrew view as
any other hypothesis.

If there be any result which has come more clearly out of geological
investigation than another, it is, that the vast series of extinct animals
and plants is not divisible, as it was once supposed to be, into distinct
groups, separated by sharply-marked boundaries. There are no great gulfs
between epochs and formations--no successive periods marked by the
appearance of plants, of water animals, and of land animals, _en
masse_. Every year adds to the list of links between what the older
geologists supposed to be widely separated epochs: witness the crags
linking the drift with older tertiaries; the Maestricht beds linking the
tertiaries with the chalk; the St. Cassian beds exhibiting an abundant
fauna of mixed mesozoic and palaeozoic types, in rocks of an epoch once
supposed to be eminently poor in life; witness, lastly, the incessant
disputes as to whether a given stratum shall be reckoned devonian or
carboniferous, silurian or devonian, cambrian or silurian.

This truth is further illustrated in a most interesting manner by the
impartial and highly competent testimony of M. Pictet, from whose
calculations of what percentage of the genera of animals, existing in any
formation, lived during the preceding formation, it results that in no case
is the proportion less than _one-third_, or 33 per cent. It is the
triassic formation, or the commencement of the mesozoic epoch, which has
received the smallest inheritance from preceding ages. The other formations
not uncommonly exhibit 60, 80, or even 94 per cent, of genera in common
with those whose remains are imbedded in their predecessor. Not only is
this true, but the subdivisions of each formation exhibit new species
characteristic of, and found only in, them; and, in many cases, as in the
lias for example, the separate beds of these subdivisions are distinguished
by well-marked and peculiar forms of life. A section, a hundred feet thick,
will exhibit, at different heights, a dozen species of ammonite, none of
which passes beyond its particular zone of limestone, or clay, into the
zone below it or into that above it; so that those who adopt the doctrine
of special creation must be prepared to admit, that at intervals of time,
corresponding with the thickness of these beds, the Creator thought fit to
interfere with the natural course of events for the purpose of making a new
ammonite. It is not easy to transplant oneself into the frame of mind of
those who can accept such a conclusion as this, on any evidence short of
absolute demonstration; and it is difficult to see what is to be gained by
so doing, since, as we have said, it is obvious that such a view of the
origin of living beings is utterly opposed to the Hebrew cosmogony.
Deserving no aid from the powerful arm of Bibliolatry, then, does the
received form of the hypothesis of special creation derive any support from
science or sound logic? Assuredly not much. The arguments brought forward
in its favour all take one form: If species were not supernaturally
created, we cannot understand the facts _x_, or _y_, or _z_;
we cannot understand the structure of animals or plants, unless we suppose
they were contrived for special ends; we cannot understand the structure of
the eye, except by supposing it to have been made to see with; we cannot
understand instincts, unless we suppose animals to have been miraculously
endowed with them.

As a question of dialectics, it must be admitted that this sort of
reasoning is not very formidable to those who are not to be frightened by
consequences. It is an _argumentum ad ignorantiam_--take this
explanation or be ignorant. But suppose we prefer to admit our ignorance
rather than adopt a hypothesis at variance with all the teachings of
Nature? Or, suppose for a moment we admit the explanation, and then
seriously ask ourselves how much the wiser are we; what does the
explanation explain? Is it any more than a grandiloquent way of announcing
the fact, that we really know nothing about the matter? A phenomenon is
explained when it is shown to be a case of some general law of Nature; but
the supernatural interposition of the Creator can, by the nature of the
case, exemplify no law, and if species have really arisen in this way, it
is absurd to attempt to discuss their origin.

Or, lastly, let us ask ourselves whether any amount of evidence which the
nature of our faculties permits us to attain, can justify us in asserting
that any phenomenon is out of the reach of natural causation. To this end
it is obviously necessary that we should know all the consequences to which
all possible combinations, continued through unlimited time, can give rise.
If we knew these, and found none competent to originate species, we should
have good ground for denying their origin by natural causation. Till we
know them, any hypothesis is better than one which involves us in such
miserable presumption.

But the hypothesis of special creation is not only a mere specious mask for
our ignorance; its existence in Biology marks the youth and imperfection of
the science. For what is the history of every science but the history of
the elimination of the notion of creative, or other interferences, with the
natural order of the phænomena which are the subject-matter of that
science? When Astronomy was young "the morning stars sang together for
joy," and the planets were guided in their courses by celestial hands. Now,
the harmony of the stars has resolved itself into gravitation according to
the inverse squares of the distances, and the orbits of the planets are
deducible from the laws of the forces which allow a schoolboy's stone to
break a window. The lightning was the angel of the Lord; but it has pleased
Providence, in these modern times, that science should make it the humble
messenger of man, and we know that every flash that shimmers about the
horizon on a summer's evening is determined by ascertainable conditions,
and that its direction and brightness might, if our knowledge of these were
great enough, have been calculated.

The solvency of great mercantile companies rests on the validity of the
laws which have been ascertained to govern the seeming irregularity of that
human life which the moralist bewails as the most uncertain of things;
plague, pestilence, and famine are admitted, by all but fools, to be the
natural result of causes for the most part fully within human control, and
not the unavoidable tortures inflicted by wrathful Omnipotence upon His
helpless handiwork.

Harmonious order governing eternally continuous progress--the web and woof
of matter and force interweaving by slow degrees, without a broken thread,
that veil which lies between us and the Infinite--that universe which alone
we know or can know; such is the picture which science draws of the world,
and in proportion as any part of that picture is in unison with the rest,
so may we feel sure that it is rightly painted. Shall Biology alone remain
out of harmony with her sister sciences?

Such arguments against the hypothesis of the direct creation of species as
these are plainly enough deducible from general considerations; but there
are, in addition, phenomena exhibited by species themselves, and yet not so
much a part of their very essence as to have required earlier mention,
which are in the highest degree perplexing, if we adopt the popularly
accepted hypothesis. Such are the facts of distribution in space and in
time; the singular phenomena brought to light by the study of development;
the structural relations of species upon which our systems of
classification are founded; the great doctrines of philosophical anatomy,
such as that of homology, or of the community of structural plan exhibited
by large groups of species differing very widely in their habits and
functions.

The species of animals which inhabit the sea on opposite sides of the
isthmus of Panama are wholly distinct;[Footnote: Recent investigations tend
to show that this statement is not strictly accurate.--1870.] the animals
and plants which inhabit islands are commonly distinct from those of the
neighbouring mainlands, and yet have a similarity of aspect. The mammals of
the latest tertiary epoch in the Old and New Worlds belong to the same
genera, or family groups, as those which now inhabit the same great
geographical area. The crocodilian reptiles which existed in the earliest
secondary epoch were similar in general structure to those now living, but
exhibit slight differences in their vertebræ, nasal passages, and one or
two other points. The guinea-pig has teeth which are shed before it is
born, and hence can never subserve the masticatory purpose for which they
seem contrived, and, in like manner, the female dugong has tusks which
never cut the gum. All the members of the same great group run through
similar conditions in their development, and all their parts, in the adult
state, are arranged according to the same plan. Man is more like a gorilla
than a gorilla is like a lemur. Such are a few, taken at random, among the
multitudes of similar facts which modern research has established; but when
the student seeks for an explanation of them from the supporters of the
received hypothesis of the origin of species, the reply he receives is, in
substance, of Oriental simplicity and brevity--"Mashallah! it so pleases
God!" There are different species on opposite sides of the isthmus of
Panama, because they were created different on the two sides. The pliocene
mammals are like the existing ones, because such was the plan of creation;
and we find rudimental organs and similarity of plan, because it has
pleased the Creator to set before Himself a "divine exemplar or archetype,"
and to copy it in His works; and somewhat ill, those who hold this view
imply, in some of them. That such verbal hocus-pocus should be received as
science will one day be regarded as evidence of the low state of
intelligence in the nineteenth century, just as we amuse ourselves with the
phraseology about Nature's abhorrence of a vacuum, wherewith Torricellis
compatriots were satisfied to explain the rise of water in a pump. And be
it recollected that this sort of satisfaction works not only negative but
positive ill, by discouraging inquiry, and so depriving man of the usufruct
of one of the most fertile fields of his great patrimony, Nature.

The objections to the doctrine of the origin of species by special creation
which have been detailed, must have occurred, with more or less force, to
the mind of every one who has seriously and independently considered the
subject. It is therefore no wonder that, from time to time, this hypothesis
should have been met by counter hypotheses, all as well, and some better
founded than itself; and it is curious to remark that the inventors of the
opposing views seem to have been led into them as much by their knowledge
of geology, as by their acquaintance with biology. In fact, when the mind
has once admitted the conception of the gradual production of the present
physical state of our globe, by natural causes operating through long ages
of time, it will be little disposed to allow that living beings have made
their appearance in another way, and the speculations of De Maillet and his
successors are the natural complement of Scilla's demonstration of the true
nature of fossils.

A contemporary of Newton and of Leibnitz, sharing therefore in the
intellectual activity of the remarkable age which witnessed the birth of
modern physical science, Benoît de Maillet spent a long life as a consular
agent of the French Government in various Mediterranean ports. For sixteen
years, in fact, he held the office of Consul-General in Egypt, and the
wonderful phenomena offered by the valley of the Nile appear to have
strongly impressed his mind, to have directed his attention to all facts of
a similar order which came within his observation, and to have led him to
speculate on the origin of the present condition of our globe and of its
inhabitants. But, with all his ardour for science, De Maillet seems to have
hesitated to publish views which, notwithstanding the ingenious attempts to
reconcile them with the Hebrew hypothesis contained in the preface to
"Telliamed," were hardly likely to be received with favour by his
contemporaries.

But a short time had elapsed since more than one of the great anatomists
and physicists of the Italian school had paid dearly for their endeavours
to dissipate some of the prevalent errors; and their illustrious pupil,
Harvey, the founder of modern physiology, had not fared so well, in a
country less oppressed by the benumbing influences of theology, as to tempt
any man to follow his example. Probably not uninfluenced by these
considerations, his Catholic majesty's Consul-General for Egypt kept his
theories to himself throughout a long life, for "Telliamed," the only
scientific work which is known to have proceeded from his pen, was not
printed till 1735, when its author had reached the ripe age of
seventy-nine; and though De Maillet lived three years longer, his book was
not given to the world before 1748. Even then it was anonymous to those who
were not in the secret of the anagrammatic character of its title; and the
preface and dedication are so worded as, in case of necessity, to give the
printer a fair chance of falling back on the excuse that the work was
intended for a mere _jeu d'esprit_.

The speculations of the suppositious Indian sage, though quite as sound as
those of many a "Mosaic Geology," which sells exceedingly well, have no
great value if we consider them by the light of modern science. The waters
are supposed to have originally covered the whole globe; to have deposited
the rocky masses which compose its mountains by processes comparable to
those which are now forming mud, sand, and shingle; and then to have
gradually lowered their level, leaving the spoils of their animal and
vegetable inhabitants embedded in the strata. As the dry land appeared,
certain of the aquatic animals are supposed to have taken to it, and to
have become gradually adapted to terrestrial and aërial modes of existence.
But if we regard the general tenor and style of the reasoning in relation
to the state of knowledge of the day, two circumstances appear very well
worthy of remark. The first, that De Maillet had a notion of the
modifiability of living forms (though without any precise information on
the subject), and how such modifiability might account for the origin of
species; the second, that he very clearly apprehended the great modern
geological doctrine, so strongly insisted upon by Hutton, and so ably and
comprehensively expounded by Lyell, that we must look to existing causes
for the explanation of past geological events. Indeed, the following
passage of the preface, in which De Maillet is supposed to speak of the
Indian philosopher Telliamed, his _alter ego,_ might have been written
by the most philosophical uniformitarian of the present day:--

"Ce qu'il y a d'étonnant, est que pour arriver à ces connaissances il
semble avoir perverti l'ordre naturel, puisqu'au lieu de s'attacher d'abord
à rechercher l'origine de notre globe il a commence par travailler à
s'instruire de la nature. Mais à l'entendre, ce renversement de l'ordre a
été pour lui l'effet d'un génie favorable qui l'a conduit pas à pas et
comme par la main aux découvertes les plus sublimes. C'est en décomposant
la substance de ce globe par tine anatomie exacte de toutes ses parties
qu'il a premierement appris de quelles matières il était composé et quels
arrangemens ces mêmes matières observaient entre elles. Ces lumieres
jointes à l'esprit de comparaison toujours nécessaire à quiconque
entreprend de percer les voiles dont la nature aime à se cacher, ont servi
de guide à notre philosophe pour parvenir à des connoissances plus
intéressantes. Par la matière et l'arrangement de ces compositions il
prétend avoir reconnu quelle est la véritable origine de ce globe que nous
habitons, comment et par qui il a été formé."-Pp. xix. xx.

But De Maillet was before his age, and as could hardly fail to happen to
one who speculated on a zoological and botanical question before Linnæus,
and on a physiological problem before Haller, he fell into great errors
here and there; and hence, perhaps, the general neglect of his work.
Robinet's speculations are rather behind, than in advance of, those of De
Maillet; and though Linnæus may have played with the hypothesis of
transmutation, it obtained no serious support until Lamarck adopted it, and
advocated it with great ability in his "Philosophie Zoologique."

Impelled towards the hypothesis of the transmutation of species, partly by
his general cosmological and geological views; partly by the conception of
a graduated, though irregularly branching, scale of being, which had arisen
out of his profound study of plants and of the lower forms of animal life,
Lamarck, whose general line of thought often closely resembles that of De
Maillet, made a great advance upon the crude and merely speculative manner
in which that writer deals with the question of the origin of living
beings, by endeavouring to find physical causes competent to effect that
change of one species into another, which De Maillet had only supposed to
occur. And Lamarck conceived that he had found in Nature such causes, amply
sufficient for the purpose in view. It is a physiological fact, he says,
that organs are increased in size by action, atrophied by inaction; it is
another physiological fact that modifications produced are transmissible to
offspring. Change the actions of an animal, therefore, and you will change
its structure, by increasing the development of the parts newly brought
into use and by the diminution of those less used; but by altering the
circumstances which surround it you will alter its actions, and hence, in
the long run, change of circumstance must produce change of organisation.
All the species of animals, therefore, are, in Lamarck's view, the result
of the indirect action of changes of circumstance, upon those primitive
germs which he considered to have originally arisen, by spontaneous
generation, within the waters of the globe. It is curious, however, that
Lamarck should insist so strongly [Footnote: See _Phil. Zoologique_,
vol. i. p. 222. et seq.] as he has done, that circumstances never in any
degree directly modify the form or the organisation of animals, but only
operate by changing their wants and consequently their actions; for he
thereby brings upon himself the obvious question, How, then, do plants,
which cannot be said to have wants or actions, become modified? To this he
replies, that they are modified by the changes in their nutritive
processes, which are effected by changing circumstances; and it does not
seem to have occurred to him that such changes might be as well supposed to
take place among animals.

When we have said that Lamarck felt that mere speculation was not the way
to arrive at the origin of species, but that it was necessary, in order to
the establishment of any sound theory on the subject, to discover by
observation or otherwise, some _vera causa_, competent to give rise to
them; that he affirmed the true order of classification to coincide with
the order of their development one from another; that he insisted on the
necessity of allowing sufficient time, very strongly; and that all the
varieties of instinct and reason were traced back by him to the same cause
as that which has given rise to species, we have enumerated his chief
contributions to the advance of the question. On the other hand, from his
ignorance of any power in Nature competent to modify the structure of
animals, except the development of parts, or atrophy of them, in
consequence of a change of needs, Lamarck was led to attach infinitely
greater weight than it deserves to this agency, and the absurdities into
which he was led have met with deserved condemnation. Of the struggle for
existence, on which, as we shall see, Mr. Darwin lays such great stress, he
had no conception; indeed, he doubts whether there really are such things
as extinct species, unless they be such large animals as may have met their
death at the hands of man; and so little does he dream of there being any
other destructive causes at work, that, in discussing the possible
existence of fossil shells, he asks, "Pourquoi d'ailleurs seroient-ils
perdues dès que l'homme n'a pu opérer leur destruction?" ("Phil. Zool.,"
vol. i. p. 77.) Of the influence of selection Lamarck has as little notion,
and he makes no use of the wonderful phenomena which are exhibited by
domesticated animals, and illustrate its powers. The vast influence of
Cuvier was employed against the Lamarckian views, and, as the untenability
of some of his conclusions was easily shown, his doctrines sank under the
opprobrium of scientific, as well as of theological, heterodoxy. Nor have
the efforts made of late years to revive them tended to re-establish their
credit in the minds of sound thinkers acquainted with the facts of the
case; indeed it may be doubted whether Lamarck has not suffered more from
his friends than from his foes.

Two years ago, in fact, though we venture to question if even the strongest
supporters of the special creation hypothesis had not, now and then, an
uneasy consciousness that all was not right, their position seemed more
impregnable than ever, if not by its own inherent strength, at any rate by
the obvious failure of all the attempts which had been made to carry it. On
the other hand, however much the few, who thought deeply on the question of
species, might be repelled by the generally received dogmas, they saw no
way of escaping from them save by the adoption of suppositions so little
justified by experiment or by observation as to be at least equally
distasteful.

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