question which has to be {58} settled before any other can be profitably
discussed, is this, What is the nature of fossils? Are they, as the healthy
common sense of the ancient Greeks appears to have led them to assume
without hesitation, the remains of animals and plants? Or are they, as was
so generally maintained in the fifteenth, sixteenth, and seventeenth
centuries, mere figured stones, portions of mineral matter which have
assumed the forms of leaves and shells and bones, just as those portions of
mineral matter which we call crystals take on the form of regular
geometrical solids? Or, again, are they, as others thought, the products of
the germs of animals and of the seeds of plants which have lost their way,
as it were, in the bowels of the earth, and have achieved only an imperfect
and abortive development? It is easy to sneer at our ancestors for being
disposed to reject the first in favour of one or other of the last two
hypotheses; but it is much more profitable to try to discover why they, who
were really not one whit less sensible persons than our excellent selves,
should have been led to entertain views which strike us as absurd. The
belief in what is erroneously called spontaneous generation, that is to
say, in the development of living matter out of mineral matter, apart from
the agency of pre-existing living matter, as an ordinary occurrence at the
present day--which is still held by some of us, was universally accepted as
an obvious truth by them. They could point to the arborescent forms assumed
by hoar-frost and by sundry metallic minerals as evidence of the existence
in nature of a "plastic {59} force" competent to enable inorganic matter to
assume the form of organised bodies. Then, as every one who is familiar
with fossils knows, they present innumerable gradations, from shells and
bones which exactly resemble the recent objects, to masses of mere stone
which, however accurately they repeat the outward form of the organic body,
have nothing else in common with it; and, thence, to mere traces and faint
impressions in the continuous substance of the rock. What we now know to be
the results of the chemical changes which take place in the course of
fossilisation, by which mineral is substituted for organic substance,
might, in the absence of such knowledge, be fairly interpreted as the
expression of a process of development in the opposite direction--from the
mineral to the organic. Moreover, in an age when it would have seemed the
most absurd of paradoxes to suggest that the general level of the sea is
constant, while that of the solid land fluctuates up and down through
thousands of feet in a secular ground swell, it may well have appeared far
less hazardous to conceive that fossils are sports of nature than to accept
the necessary alternative, that all the inland regions and highlands, in
the rocks of which marine shells had been found, had once been covered by
the ocean. It is not so surprising, therefore, as it may at first seem,
that although such men as Leonardo da Vinci and Bernard Palissy took just
views of the nature of fossils, the opinion of the majority of their
contemporaries set strongly the other way; nor even that error maintained
itself long after the {60} scientific grounds of the true interpretation of
fossils had been stated, in a manner that left nothing to be desired, in
the latter half of the seventeenth century. The person who rendered this
good service to palaeontology was Nicolas Steno, professor of anatomy in
Florence, though a Dane by birth. Collectors of fossils at that day were
familiar with certain bodies termed "glossopetrae," and speculation was rife
as to their nature. In the first half of the seventeenth century, Fabio
Colonna had tried to convince his colleagues of the famous Accademia dei
Lincei that the glossopetrae were merely fossil sharks' teeth, but his
arguments made no impression. Fifty years later, Steno reopened the
question, and, by dissecting the head of a shark and pointing out the very
exact correspondence of its teeth with the glossopetrae, left no rational
doubt as to the origin of the latter. Thus far, the work of Steno went
little further than that of Colonna, but it fortunately occurred to him to
think out the whole subject of the interpretation of fossils, and the
result of his meditations was the publication, in 1669, of a little
treatise with the very quaint title of _De Solido intra Solidum naturaliter
contento_. The general course of Steno's argument may be stated in a few
words. Fossils are solid bodies which, by some natural process, have come
to be contained within other solid bodies, namely, the rocks in which they
are embedded; and the fundamental problem of palaeontology, stated
generally, is this: "Given a body endowed with a certain shape and produced
in accordance with natural laws, to find {61} in that body itself the
evidence of the place and manner of its production."[8] The only way of
solving this problem is by the application of the axiom that "like effects
imply like causes," or as Steno puts it, in reference to this particular
case, that "bodies which are altogether similar have been produced in the
same way."[9] Hence, since the glossopetrae are altogether similar to
sharks' teeth, they must have been produced by sharklike fishes; and since
many fossil shells correspond, down to the minutest details of structure,
with the shells of existing marine or freshwater animals, they must have
been produced by similar animals; and the like reasoning is applied by
Steno to the fossil bones of vertebrated animals, whether aquatic or
terrestrial. To the obvious objection that many fossils are not altogether
similar to their living analogues, differing in substance while agreeing in
form, or being mere hollows or impressions, the surfaces of which are
figured in the same way as those of animal or vegetable organisms, Steno
replies by pointing out the changes which take place in organic remains
embedded in the earth, and how their solid substance may be dissolved away
entirely, or replaced by mineral matter, until nothing is left of the
original but a cast, an impression, or a mere trace of its contours. The
principles of investigation thus excellently stated and illustrated by
Steno in 1669, are those which have, {62} consciously or unconsciously,
guided the researches of palaeontologists ever since. Even that feat of
palaeontology which has so powerfully impressed the popular imagination, the
reconstruction of an extinct animal from a tooth or a bone, is based upon
the simplest imaginable application of the logic of Steno. A moment's
consideration will show, in fact, that Steno's conclusion that the
glossopetrae are sharks' teeth implies the reconstruction of an animal from
its tooth. It is equivalent to the assertion that the animal of which the
glossopetrae are relics had the form and organisation of a shark; that it
had a skull, a vertebral column, and limbs similar to those which are
characteristic of this group of fishes; that its heart, gills, and
intestines presented the peculiarities which those of all sharks exhibit;
nay, even that any hard parts which its integument contained were of a
totally different character from the scales of ordinary fishes. These
conclusions are as certain as any based upon probable reasonings can be.
And they are so, simply because a very large experience justifies us in
believing that teeth of this particular form and structure are invariably
associated with the peculiar organisation of sharks, and are never found in
connection with other organisms. Why this should be we are not at present
in a position even to imagine; we must take the fact as an empirical law of
animal morphology, the reason of which may possibly be one day found in the
history of the evolution of the shark tribe, but for which it is hopeless
to seek for an explanation in ordinary physiological reasonings. Every one
{63} practically acquainted with palaeontology is aware that it is not every
tooth, nor every bone, which enables us to form a judgment of the character
of the animal to which it belonged; and that it is possible to possess many
teeth, and even a large portion of the skeleton of an extinct animal, and
yet be unable to reconstruct its skull or its limbs. It is only when the
tooth or bone presents peculiarities, which we know by previous experience
to be characteristic of a certain group, that we can safely predict that
the fossil belonged to an animal of the same group. Any one who finds a
cow's grinder may be perfectly sure that it belonged to an animal which had
two complete toes on each foot and ruminated; any one who finds a horse's
grinder may be as sure that it had one complete toe on each foot and did
not ruminate; but if ruminants and horses were extinct animals of which
nothing but the grinders had ever been discovered, no amount of
physiological reasoning could have enabled us to reconstruct either animal,
still less to have divined the wide differences between the two. Cuvier, in
the _Discours sur les Revolutions de la Surface du Globe_, strangely
credits himself, and has ever since been credited by others, with the
invention of a new method of palaeontological research. But if you will turn
to the _Recherches sur les Ossemens Fossiles_ and watch Cuvier, not
speculating, but working, you will find that his method is neither more nor
less than that of Steno. If he was able to make his famous prophecy from
the jaw which lay upon the surface of a block of stone to the pelvis of the
same animal which lay hidden in it, it was not {64} because either he, or
any one else, knew, or knows, why a certain form of jaw is, as a rule,
constantly accompanied by the presence of marsupial bones, but simply
because experience has shown that these two structures are co-ordinated.
The settlement of the nature of fossils led at once to the next advance of
palaeontology, viz. its application to the deciphering of the history of the
earth. When it was admitted that fossils are remains of animals and plants,
it followed that, in so far as they resemble terrestrial, or freshwater,
animals and plants, they are evidences of the existence of land, or fresh
water; and, in so far as they resemble marine organisms, they are evidences
of the existence of the sea at the time at which they were parts of
actually living animals and plants. Moreover, in the absence of evidence to
the contrary, it must be admitted that the terrestrial or the marine
organisms implied the existence of land or sea at the place in which they
were found while they were yet living. In fact, such conclusions were
immediately drawn by everybody, from the time of Xenophanes downwards, who
believed that fossils were really organic remains. Steno discusses their
value as evidence of repeated alteration of marine and terrestrial
conditions upon the soil of Tuscany in a manner worthy of a modern
geologist. The speculations of De Maillet in the beginning of the
eighteenth century turn upon fossils; and Buffon follows him very closely
in those two remarkable works, the _Theorie de la Terre_ and the _Epoques
de la Nature_, with {65} which he commenced and ended his career as a
naturalist.
The opening sentences of the _Epoques de la Nature_ show us how fully
Buffon recognised the analogy of geological with archaeological inquiries.
"As in civil history we consult deeds, seek for coins, or decipher antique
inscriptions in order to determine the epochs of human revolutions and fix
the date of moral events; so, in natural history, we must search the
archives of the world, recover old monuments from the bowels of the earth,
collect their fragmentary remains, and gather into one body of evidence all
the signs of physical change which may enable us to look back upon the
different ages of nature. It is our only means of fixing some points in the
immensity of space, and of setting a certain number of waymarks along the
eternal path of time."
Buffon enumerates five classes of these monuments of the past history of
the earth, and they are all facts of palaeontology. In the first place, he
says, shells and other marine productions are found all over the surface
and in the interior of the dry land; and all calcareous rocks are made up
of their remains. Secondly, a great many of these shells which are found in
Europe are not now to be met with in the adjacent seas; and, in the slates
and other deep-seated deposits, there are remains of fishes and of plants
of which no species now exist in our latitudes, and which are either
extinct, or exist only in more northern climates. Thirdly, in Siberia and
in other northern regions of Europe and of Asia, bones and {66} teeth of
elephants, rhinoceroses, and hippopotamuses occur in such numbers that
these animals must once have lived and multiplied in those regions,
although at the present day they are confined to southern climates. The
deposits in which these remains are found are superficial, while those
which contain shells and other marine remains lie much deeper. Fourthly,
tusks and bones of elephants and hippopotamuses are found not only in the
northern regions of the old world, but also in those of the new world,
although, at present, neither elephants nor hippopotamuses occur in
America. Fifthly, in the middle of the continents, in regions most remote
from the sea, we find an infinite number of shells, of which the most part
belong to animals of those kinds which still exist in southern seas, but of
which many others have no living analogues; so that these species appear to
be lost, destroyed by some unknown cause. It is needless to inquire how far
these statements are strictly accurate; they are sufficiently so to justify
Buffon's conclusions that the dry land was once beneath the sea; that the
formation of the fossiliferous rocks must have occupied a vastly greater
lapse of time than that traditionally ascribed to the age of the earth;
that fossil remains indicate different climatal conditions to have obtained
in former times, and especially that the polar regions were once warmer;
that many species of animals and plants have become extinct; and that
geological change has had something to do with geographical distribution.
But these propositions almost constitute the framework of palaeontology. In
order to complete it but {67} one addition was needed, and that was made,
in the last years of the eighteenth century, by William Smith, whose work
comes so near our own times that many living men may have been personally
acquainted with him. This modest land-surveyor, whose business took him
into many parts of England, profited by the peculiarly favourable
conditions offered by the arrangement of our secondary strata to make a
careful examination and comparison of their fossil contents at different
points of the large area over which they extend. The result of his accurate
and widely-extended observations was to establish the important truth that
each stratum contains certain fossils which are peculiar to it; and that
the order in which the strata, characterised by these fossils, are
superimposed one upon the other is always the same. This most important
generalisation was rapidly verified and extended to all parts of the world
accessible to geologists; and now it rests upon such an immense mass of
observations as to be one of the best established truths of natural
science. To the geologist the discovery was of infinite importance, as it
enabled him to identify rocks of the same relative age, however their
continuity might be interrupted or their composition altered. But to the
biologist it had a still deeper meaning, for it demonstrated that,
throughout the prodigious duration of time registered by the fossiliferous
rocks, the living population of the earth had undergone continual changes,
not merely by the extinction of a certain number of the species which had
at first existed, but by the continual generation {68} of new species, and
the no less constant extinction of old ones.
Thus the broad outlines of palaeontology, in so far as it is the common
property of both the geologist and the biologist, were marked out at the
close of the last century. In tracing its subsequent progress I must
confine myself to the province of biology, and, indeed, to the influence of
palaeontology upon zoological morphology. And I accept this limitation the
more willingly as the no less important topic of the bearing of geology and
of palaeontology upon distribution has been luminously treated in the
address of the President of the Geographical Section.[10]
The succession of the species of animals and plants in time being
established, the first question which the zoologist or the botanist had to
ask himself was, What is the relation of these successive species one to
another? And it is a curious circumstance that the most important event in
the history of palaeontology which immediately succeeded William Smith's
generalisation was a discovery which, could it have been rightly
appreciated at the time, would have gone far towards suggesting the answer,
which was in fact delayed for more than half a century. I refer to Cuvier's
investigation of the Mammalian fossils yielded by the quarries in the older
tertiary rocks of Montmartre, among the chief results of which was the
bringing to light of two genera of extinct hoofed quadrupeds, the
_Anoplotherium_ and the _Palaeotherium_. The rich materials at Cuvier's
disposition enabled him {69} to obtain a full knowledge of the osteology
and of the dentition of these two forms, and consequently to compare their
structure critically with that of existing hoofed animals. The effect of
this comparison was to prove that the _Anoplotherium_, though it presented
many points of resemblance with the pigs on the one hand and with the
ruminants on the other, differed from both to such an extent that it could
find a place in neither group. In fact, it held, in some respects, an
intermediate position, tending to bridge over the interval between these
two groups, which in the existing fauna are so distinct. In the same way,
the _Palaeotherium_ tended to connect forms so different as the tapir, the
rhinoceros, and the horse. Subsequent investigations have brought to light
a variety of facts of the same order, the most curious and striking of
which are those which prove the existence, in the mesozoic epoch, of a
series of forms intermediate between birds and reptiles--two classes of
vertebrate animals which at present appear to be more widely separated than
any others. Yet the interval between them is completely filled, in the
mesozoic fauna, by birds which have reptilian characters on the one side,
and reptiles which have ornithic characters on the other. So again, while
the group of fishes termed ganoids is at the present time so distinct from
that of the dipnoi, or mudfishes, that they have been reckoned as distinct
orders, the Devonian strata present us with forms of which it is impossible
to say with certainty whether they are dipnoi or whether they are ganoids.
{70}
Agassiz's long and elaborate researches upon fossil fishes, published
between 1833 and 1842, led him to suggest the existence of another kind of
relation between ancient and modern forms of life. He observed that the
oldest fishes present many characters which recall the embryonic conditions
of existing fishes; and that, not only among fishes, but in several groups
of the invertebrata which have a long palaeontological history, the latest
forms are more modified, more specialised, than the earlier. The fact that
the dentition of the older tertiary ungulate and carnivorous mammals is
always complete, noticed by Professor Owen, illustrated the same
generalisation.
Another no less suggestive observation was made by Mr. Darwin, whose
personal investigations during the voyage of the _Beagle_ led him to remark
upon the singular fact, that the fauna, which immediately precedes that at
present existing in any geographical province of distribution, presents the
same peculiarities as its successor. Thus, in South America and in
Australia, the later tertiary or quaternary fossils show that the fauna
which immediately preceded that of the present day was, in the one case, as
much characterised by edentates and, in the other, by marsupials as it is
now, although the species of the older are largely different from those of
the newer fauna.
However clearly these indications might point in one direction, the
question of the exact relation of the successive forms of animal and
vegetable life could be satisfactorily settled only in one way; namely, by
comparing, stage by stage, the series of {71} forms presented by one and
the same type throughout a long space of time. Within the last few years
this has been done fully in the case of the horse, less completely in the
case of the other principal types of the ungulata and of the carnivora; and
all these investigations tend to one general result, namely, that, in any
given series, the successive members of that series present a gradually
increasing specialisation of structure. That is to say, if any such mammal
at present existing has specially modified and reduced limbs or dentition
and complicated brain, its predecessors in time show less and less
modification and reduction in limbs and teeth and a less highly developed
brain. The labours of Gaudry, Marsh, and Cope furnish abundant
illustrations of this law from the marvellous fossil wealth of Pikermi and
the vast uninterrupted series of tertiary rocks in the territories of North
America.
I will now sum up the results of this sketch of the rise and progress of
palaeontology. The whole fabric of palaeontology is based upon two
propositions: the first is, that fossils are the remains of animals and
plants; and the second is, that the stratified rocks in which they are
found are sedimentary deposits; and each of these propositions is founded
upon the same axiom, that like effects imply like causes. If there is any
cause competent to produce a fossil stem, or shell, or bone, except a
living being, then palaeontology has no foundation; if the stratification of
the rocks is not the effect of such causes as at present produce {72}
stratification, we have no means of judging of the duration of past time,
or of the order in which the forms of life have succeeded one another. But
if these two propositions are granted, there is no escape, as it appears to
me, from three very important conclusions. The first is that living matter
has existed upon the earth for a vast length of time, certainly for
millions of years. The second is that, during this lapse of time, the forms
of living matter have undergone repeated changes, the effect of which has
been that the animal and vegetable population, at any period of the earth's
history, contains some species which did not exist at some antecedent
period, and others which ceased to exist at some subsequent period. The
third is that, in the case of many groups of mammals and some of reptiles,
in which one type can be followed through a considerable extent of
geological time, the series of different forms by which the type is
represented, at successive intervals of this time, is exactly such as it
would be, if they had been produced by the gradual modification of the
earliest forms of the series. These are facts of the history of the earth
guaranteed by as good evidence as any facts in civil history.
Hitherto I have kept carefully clear of all the hypotheses to which men
have at various times endeavoured to fit the facts of palaeontology, or by
which they have endeavoured to connect as many of these facts as they
happened to be acquainted with. I do not think it would be a profitable
employment of our time to discuss conceptions which doubtless have had
their justification and even their use, but which {73} are now obviously
incompatible with the well-ascertained truths of palaeontology. At present
these truths leave room for only two hypotheses. The first is that, in the
course of the history of the earth, innumerable species of animals and
plants have come into existence, independently of one another, innumerable
times. This, of course, implies either that spontaneous generation on the
most astounding scale, and of animals such as horses and elephants, has
been going on, as a natural process, through all the time recorded by the
fossiliferous rocks; or it necessitates the belief in innumerable acts of
creation repeated innumerable times. The other hypothesis is, that the
successive species of animals and plants have arisen, the later by the
gradual modification of the earlier. This is the hypothesis of evolution;
and the palaeontological discoveries of the last decade are so completely in
accordance with the requirements of this hypothesis that, if it had not
existed, the palaeontologist would have had to invent it.
I have always had a certain horror of presuming to set a limit upon the
possibilities of things. Therefore I will not venture to say that it is
impossible that the multitudinous species of animals and plants may have
been produced, one separately from the other, by spontaneous generation;
nor that it is impossible that they should have been independently
originated by an endless succession of miraculous creative acts. But I must
confess that both these hypotheses strike me as so astoundingly improbable,
so devoid of a shred of either scientific or traditional support, that even
if {74} there were no other evidence than that of palaeontology in its
favour, I should feel compelled to adopt the hypothesis of evolution.
Happily, the future of palaeontology is independent of all hypothetical
considerations. Fifty years hence, whoever undertakes to record the
progress of palaeontology will note the present time as the epoch in which
the law of succession of the forms of the higher animals was determined by
the observation of palaeontological facts. He will point out that, just as
Steno and as Cuvier were enabled from their knowledge of the empirical laws
of coexistence of the parts of animals to conclude from a part to the
whole, so the knowledge of the law of succession of forms empowered their
successors to conclude, from one or two terms of such a succession, to the
whole series; and thus to divine the existence of forms of life, of which,
perhaps, no trace remains, at epochs of inconceivable remoteness in the
past.
* * * * *
{75}
II
THE INTERPRETERS OF GENESIS AND THE INTERPRETERS OF NATURE
Our fabulist warns "those who in quarrels interpose" of the fate which is
probably in store for them; and, in venturing to place myself between so
powerful a controversialist as Mr. Gladstone and the eminent divine whom he
assaults with such vigour in the last number of this Review,[11] I am fully
aware that I run great danger of verifying Gay's prediction. Moreover, it
is quite possible that my zeal in offering aid to a combatant so extremely
well able to take care of himself as M. Reville may be thought to savour of
indiscretion.
Two considerations, however, have led me to face the double risk. The one
is that though, in my judgment, M. Reville is wholly in the right in that
part of the controversy to which I propose to restrict my observations,
nevertheless he, as a foreigner, has very little chance of making the truth
prevail with Englishmen against the authority and the dialectic skill of
the greatest master of persuasive rhetoric among English-speaking men of
our time. {76} As the Queen's proctor intervenes, in certain cases, between
two litigants in the interests of justice, so it may be permitted me to
interpose as a sort of uncommissioned science proctor. My second excuse for
my meddlesomeness is, that important questions of natural
science--respecting which neither of the combatants professes to speak as
an expert--are involved in the controversy; and I think it is desirable
that the public should know what it is that natural science really has to
say on these topics, to the best belief of one who has been a diligent
student of natural science for the last forty years.
The original _Prolegomenes de l'histoire des Religions_ has not come in my
way; but I have read the translation of M. Reville's work, published in
England under the auspices of Professor Max Mueller, with very great
interest. It puts more fairly and clearly than any book previously known to
me, the view which a man of strong religious feelings, but at the same time
possessing the information and the reasoning power which enable him to
estimate the strength of scientific methods of inquiry and the weight of
scientific truth, may be expected to take of the relation between science
and religion.
In the chapter on "The Primitive Revelation" the scientific worth of the
account of the Creation given in the book of Genesis is estimated in terms
which are as unquestionably respectful as, in my judgment, they are just;
and, at the end of the chapter on "Primitive Tradition," M. Reville
appraises the value of pentateuchal anthropology in a way which I should
{77} have thought sure of enlisting the assent of all competent judges,
even if it were extended to the whole of the cosmogony and biology of
Genesis:--
As, however, the original traditions of nations sprang up in an epoch
less remote than our own from the primitive life, it is indispensable
to consult them, to compare them, and to associate them with other
sources of information which are available. From this point of view,
the traditions recorded in Genesis possess, in addition to their own
peculiar charm, a value of the highest order; but we cannot ultimately
see in them more than a venerable fragment, well deserving attention,
of the great genesis of mankind.
Mr. Gladstone is of a different mind. He dissents from M. Reville's views
respecting the proper estimation of the pentateuchal traditions, no less
than he does from his interpretation of those Homeric myths which have been
the object of his own special study. In the latter case, Mr. Gladstone
tells M. Reville that he is wrong on his own authority, to which, in such a
matter, all will pay due respect: in the former, he affirms himself to be
"wholly destitute of that kind of knowledge which carries authority," and
his rebuke is administered in the name and by the authority of natural
science.
An air of magisterial gravity hangs about the following passage:--
But the question is not here of a lofty poem, or a skilfully
constructed narrative: it is whether natural science, in the patient
exercise of its high calling to examine facts, finds that the works of
God cry out against what we have fondly believed to be His word and
tell another tale; or whether, in this nineteenth century of Christian
progress, it substantially echoes back the majestic sound, which,
before it existed as a pursuit, went forth into all lands. {78}
First, looking largely at the latter portion of the narrative, which
describes the creation of living organisms, and waiving details, on
some of which (as in v. 24) the Septuagint seems to vary from the
Hebrew, there is a grand fourfold division, set forth in an orderly
succession of times as follows: on the fifth day
1. The water-population;
2. The air-population;
and, on the sixth day,
3. The land-population of animals;
4. The land-population consummated in man.
Now this same fourfold order is understood to have been so affirmed in
our time by natural science, that it may be taken as a demonstrated
conclusion and established fact (p. 696).
"Understood?" By whom? I cannot bring myself to imagine that Mr. Gladstone
has made so solemn and authoritative a statement on a matter of this
importance without due inquiry--without being able to found himself upon
recognised scientific authority. But I wish he had thought fit to name the
source from whence he has derived his information, as, in that case, I
could have dealt with his authority, and I should have thereby escaped the
appearance of making an attack on Mr. Gladstone himself, which is in every
way distasteful to me.
For I can meet the statement in the last paragraph of the above citation
with nothing but a direct negative. If I know anything at all about the
results attained by the natural science of our time, it is "a demonstrated
conclusion and established fact" that the "fourfold order" given by Mr.
Gladstone is not that in which the evidence at our disposal {79} tends to
show that the water, air, and land-populations of the globe have made their
appearance.