Antiquity and Persistence in Character of the existing Races
of Mankind.
Theory of their Unity of Origin considered.
Bearing of the Diversity of Races on the Doctrine of Transmutation.
Difficulty of defining the Terms "Species" and "Race."
Lamarck's Introduction of the Element of Time into the
Definition of a Species.
His Theory of Variation and Progression.
Objections to his Theory, how far answered.
Arguments of modern Writers in favour of Progression in the
Animal and Vegetable World.
The old Landmarks supposed to indicate the first Appearance of Man,
and of different Classes of Animals, found to be erroneous.
Yet the Theory of an advancing Series of Organic Beings not
inconsistent with Facts.
Earliest known Fossil Mammalia of low Grade.
No Vertebrata as yet discovered in the oldest Fossiliferous Rocks.
Objections to the Theory of Progression considered.
Causes of the Popularity of the Doctrine of Progression as compared
to that of Transmutation.
When speaking in a former work of the distinct races of mankind,* I
remarked that, "if all the leading varieties of the human family sprang
originally from a single pair" (a doctrine, to which then, as now,
I could see no valid objection), "a much greater lapse of time was
required for the slow and gradual formation of such races as the
Caucasian, Mongolian, and Negro, than was embraced in any of the popular
systems of chronology."
(* "Principles of Geology" 7th edition page 637, 1847; see
also 9th edition page 660.)
In confirmation of the high antiquity of two of these, I referred to
pictures on the walls of ancient temples in Egypt, in which, a thousand
years or more before the Christian era, "the Negro and Caucasian
physiognomies were portrayed as faithfully, and in as strong contrast,
as if the likenesses of these races had been taken yesterday." In
relation to the same subject, I dwelt on the slight modification which
the Negro has undergone, after having been transported from the tropics
and settled for more than two centuries in the temperate climate of
Virginia. I therefore concluded that, "if the various races were
all descended from a single pair, we must allow for a vast series of
antecedent ages, in the course of which the long-continued influence
of external circumstances gave rise to peculiarities increased in many
successive generations and at length fixed by hereditary transmission."
So long as physiologists continued to believe that Man had not existed
on the earth above six thousand years, they might with good reason
withhold their assent from the doctrine of a unity of origin of so many
distinct races but the difficulty becomes less and less, exactly in
proportion as we enlarge our ideas of the lapse of time during which
different communities may have spread slowly, and become isolated,
each exposed for ages to a peculiar set of conditions, whether of
temperature, or food, or danger, or ways of living. The law of the
geometrical rate of the increase of population which causes it always
to press hard on the means of subsistence, would ensure the migration in
various directions of offshoots from the society first formed abandoning
the area where they had multiplied. But when they had gradually
penetrated to remote regions by land or water--drifted sometimes
by storms and currents in canoes to an unknown shore--barriers of
mountains, deserts, or seas, which oppose no obstacle to mutual
intercourse between civilised nations, would ensure the complete
isolation for tens or thousands of centuries of tribes in a primitive
state of barbarism.
Some modern ethnologists, in accordance with the philosophers of
antiquity, have assumed that men at first fed on the fruits of the
earth, before even a stone implement or the simplest form of canoe had
been invented. They may, it is said, have begun their career in some
fertile island in the tropics, where the warmth of the air was such that
no clothing was needed and where there were no wild beasts to endanger
their safety. But as soon as their numbers increased they would be
forced to migrate into regions less secure and blest with a less genial
climate. Contests would soon arise for the possession of the most
fertile lands, where game or pasture abounded and their energies and
inventive powers would be called forth, so that at length they would
make progress in the arts.
But as ethnologists have failed, as yet, to trace back the history
of any one race to the area where it originated, some zoologists of
eminence have declared their belief that the different races, whether
they be three, five, twenty, or a much greater number (for on this point
there is an endless diversity of opinion),* have all been primordial
creations, having from the first been stamped with the characteristic
features, mental and bodily, by which they are now distinguished, except
where intermarriage has given rise to mixed or hybrid races.
(* See "Transactions of the Ethnological Society" volume 1
1861.)
Were we to admit, say they, a unity of origin of such strongly marked
varieties as the Negro and European, differing as they do in colour and
bodily constitution, each fitted for distinct climates and exhibiting
some marked peculiarities in their osteological, and even in some
details of cranial and cerebral conformation, as well as in their
average intellectual endowments--if, in spite of the fact that all these
attributes have been faithfully handed down unaltered for hundreds of
generations, we are to believe that, in the course of time, they have
all diverged from one common stock, how shall we resist the arguments
of the transmutationist, who contends that all closely allied species of
animals and plants have in like manner sprung from a common parentage,
albeit that for the last three or four thousand years they may have been
persistent in character? Where are we to stop, unless we make our stand
at once on the independent creation of those distinct human races, the
history of which is better known to us than that of any of the inferior
animals?
So long as Geology had not lifted up a part of the veil which formerly
concealed from the naturalist the history of the changes which the
animate creation had undergone in times immediately antecedent to
the Recent period, it was easy to treat these questions as too
transcendental, or as lying too far beyond the domain of positive
science to require serious discussion. But it is no longer possible
to restrain curiosity from attempting to pry into the relations which
connect the present state of the animal and vegetable worlds, as well as
of the various races of mankind, with the state of the fauna and flora
which immediately preceded.
In the very outset of the inquiry, we are met with the difficulty
of defining what we mean by the terms "species" and "race;" and the
surprise of the unlearned is usually great, when they discover how wide
is the difference of opinion now prevailing as to the significance of
words in such familiar use. But, in truth, we can come to no agreement
as to such definitions, unless we have previously made up our minds
on some of the most momentous of all the enigmas with which the human
intellect ever attempted to grapple.
It is now thirty years since I gave an analysis in the first edition of
my "Principles of Geology" (volume 2 1832) of the views which had been
put forth by Lamarck, in the beginning of the century, on this subject.
In that interval the progress made in zoology and botany, both in
augmenting the number of known animals and plants, and in studying their
physiology and geographical distribution and above all in examining and
describing fossil species, is so vast that the additions made to our
knowledge probably exceed all that was previously known; and what
Lamarck then foretold has come to pass; the more new forms have been
multiplied, the less are we able to decide what we mean by a variety,
and what by a species. In fact, zoologists and botanists are not only
more at a loss than ever how to define a species, but even to determine
whether it has any real existence in nature, or is a mere abstraction of
the human intellect, some contending that it is constant within certain
narrow and impassable limits of variability, others that it is capable
of indefinite and endless modification.
Before I attempt to explain a great step, which has recently been made
by Mr. Darwin and his fellow-labourers in this field of inquiry, I think
it useful to recapitulate in this place some of the leading features of
Lamarck's system, without attempting to adjust the claims of some of
his contemporaries (Geoffroy St. Hilaire in particular) to share in the
credit of some of his original speculations.
From the time of Linnaeus to the commencement of the present century,
it seemed a sufficient definition of the term species to say that
"a species consisted of individuals all resembling each other, and
reproducing their like by generation." But Lamarck after having
first studied botany with success, had then turned his attention to
conchology, and soon became aware that in the newer (or Tertiary) strata
of the earth's crust there were a multitude of fossil species of shells,
some of them identical with living ones, others simply varieties of the
living, and which as such were entitled to be designated, according
to the ordinary rules of classification, by the same names. He also
observed that other shells were so nearly allied to living forms that
it was difficult not to suspect that they had been connected by a common
bond of descent. He therefore proposed that the element of time should
enter into the definition of a species, and that it should run thus:
"A species consists of individuals all resembling each other, and
reproducing their like by generation, SO LONG AS THE SURROUNDING
CONDITIONS DO NOT UNDERGO CHANGES SUFFICIENT TO CAUSE THEIR HABITS,
CHARACTERS, AND FORMS TO VARY." He came at last to the conclusion that
none of the animals and plants now existing were primordial creations,
but were all derived from pre-existing forms, which, after they may have
gone on for indefinite ages reproducing their like, had at length, by
the influence of alterations in climate and in the animate world been
made to vary gradually, and adapt themselves to new circumstances, some
of them deviating in the course of ages so far from their original type
as to have claims to be regarded as new species.
In support of these views, he referred to wild and cultivated plants and
to wild and domesticated animals, pointing out how their colour, form,
structure, physiological attributes and even instincts were gradually
modified by exposure to new soils and climates, new enemies, modes of
subsistence, and kinds of food.
Nor did he omit to notice that the newly acquired peculiarities may
be inherited by the offspring for an indefinite series of generations,
whether they be brought about naturally--as when a species, on the
extreme verge of its geographical range, comes into competition with
new antagonists and is subjected to new physical conditions; or
artificially--as when by the act of the breeder or horticulturist
peculiar varieties of form or disposition are selected.
But Lamarck taught not only that species had been constantly undergoing
changes from one geological period to another, but that there also had
been a progressive advance of the organic world from the earliest to
the latest times, from beings of the simplest to those of more and more
complex structure, and from the lowest instincts up to the highest,
and finally from brute intelligence to the reasoning powers of Man. The
improvement in the grade of being had been slow and continuous, and the
human race itself was at length evolved out of the most highly organised
and endowed of the inferior mammalia.
In order to explain how, after an indefinite lapse of ages, so many of
the lowest grades of animal or plant still abounded, he imagined that
the germs or rudiments of living things, which he called monads, were
continually coming into the world and that there were different kinds
of these monads for each primary division of the animal and vegetable
kingdoms. This last hypothesis does not seem essentially different from
the old doctrine of equivocal or spontaneous generation; it is wholly
unsupported by any modern experiments or observation, and therefore
affords us no aid whatever in speculating on the commencement of vital
phenomena on the earth.
Some of the laws which govern the appearance of new varieties were
clearly pointed out by Lamarck. He remarked, for example, that as the
muscles of the arm become strengthened by exercise or enfeebled by
disuse, some organs may in this way, in the course of time, become
entirely obsolete, and others previously weak become strong and play a
new or more leading part in the organisation of a species. And so
with instincts, where animals experience new dangers they become more
cautious and cunning, and transmit these acquired faculties to their
posterity. But not satisfied with such legitimate speculations, the
French philosopher conceived that by repeated acts of volition animals
might acquire new organs and attributes, and that in plants, which
could not exert a will of their own, certain subtle fluids or organising
forces might operate so as to work out analogous effects.
After commenting on these purely imaginary causes, I pointed out in
1832, as the two great flaws in Lamarck's attempt to explain the origin
of species, first, that he had failed to adduce a single instance of
the initiation of a new organ in any species of animal or plant; and
secondly, that variation, whether taking place in the course of nature
or assisted artificially by the breeder and horticulturist, had never
yet gone so far as to produce two races sufficiently remote from each
other in physiological constitution as to be sterile when intermarried,
or, if fertile, only capable of producing sterile hybrids, etc.*
(* "Principles of Geology" 1st edition volume 2 chapter 2.)
To this objection Lamarck would, no doubt, have answered that there had
not been time for bringing about so great an amount of variation;
for when Cuvier and some other of his contemporaries appealed to the
embalmed animals and plants taken from Egyptian tombs, some of them 3000
years old, which had not experienced in that long period the slightest
modification in their specific characters, he replied that the climate
and soil of the valley of the Nile had not varied in the interval, and
that there was therefore no reason for expecting that we should be able
to detect any change in the fauna and flora. "But if," he went on to
say, "the physical geography, temperature, and other conditions of life
had been altered in Egypt as much as we know from geology has happened
in other regions, some of the same animals and plants would have
deviated so far from their pristine types as to be thought entitled to
take rank as new and distinct species."
Although I cited this answer of Lamarck in my account of his theory,*
I did not at the time fully appreciate the deep conviction which it
displays of the slow manner in which geological changes have taken place
and the insignificance of thirty or forty centuries in the history of
a species, and that, too, at a period when very narrow views were
entertained of the extent of past time by most of the ablest geologists,
and when great revolutions of the earth's crust, and its inhabitants,
were generally attributed to sudden and violent catastrophes.
(* Ibid. page 587.)
While in 1832 I argued against Lamarck's doctrine of the gradual
transmutation of one species into another, I agreed with him in
believing that the system of changes now in progress in the organic
world would afford, when fully understood, a complete key to the
interpretation of all the vicissitudes of the living creation in past
ages. I contended against the doctrine, then very popular, of the sudden
destruction of vast multitudes of species and the abrupt ushering into
the world of new batches of plants and animals.
I endeavoured to sketch out (and it was, I believe, the first systematic
attempt to accomplish such a task) the laws which govern the extinction
of species, with a view of showing that the slow but ceaseless
variations now in progress in physical geography, together with the
migration of plants and animals into new regions, must in the course
of ages give rise to the occasional loss of some of them and eventually
cause an entire fauna and flora to die out; also that we must infer from
geological data that the places thus left vacant from time to time
are filled up without delay by new forms adapted to new conditions,
sometimes by immigration from adjoining provinces, sometimes by new
creations. Among the many causes of extinction enumerated by me were the
power of hostile species, diminution of food, mutations in climate, the
conversion of land into sea and of sea into land, etc. I firmly opposed
Brocchi's hypothesis of a decline in the vital energy of each species;*
maintaining that there was every reason to believe that the reproductive
powers of the last surviving representatives of a species were as
vigorous as those of their predecessors, and that they were as capable,
under favourable circumstances, of repeopling the earth with their kind.
(* "Principles of Geology" 1st edition volume 2 chapter 8;
and 9th edition page 668.)
The manner in which some species are now becoming scarce and dying out,
one after the other, appeared to me to favour the doctrine of the fixity
of the specific character, showing a want of pliancy and capability of
varying, which ensured their annihilation whenever changes adverse
to their well-being occurred; time not being allowed for such a
transformation as might be conceived capable of adapting them to the new
circumstances, and of converting them into what naturalists would call
new species.*
(* Laws of Extinction, "Principles of Geology" 1st edition
1832 volume 2 chapters 5 to 11 inclusive; and 9th edition
chapters 37 to 42 inclusive 1853.)
But while rejecting transmutation, I was equally opposed to the popular
theory that the creative power had diminished in energy, or that it
had been in abeyance ever since Man had entered upon the scene. That a
renovating force which had been in full operation for millions of years
should cease to act while the causes of extinction were still in full
activity, or even intensified by the accession of Man's destroying
power, seemed to me in the highest degree improbable. The only point on
which I doubted was whether the force might not be intermittent instead
of being, as Lamarck supposed, in ceaseless operation. Might not the
births of new species, like the deaths of old ones, be sudden? Might
they not still escape our observation? If the coming in of one new
species, and the loss of one other which had endured for ages, should
take place annually, still, assuming that there are a million of animals
and plants living on the globe, it would require, I observed, a million
of years to bring about a complete revolution in the fauna and flora. In
that case, I imagined that, although the first appearance of a new form
might be as abrupt as the disappearance of an old one, yet naturalists
might never yet have witnessed the first entrance on the stage of a
large and conspicuous animal or plant, and as to the smaller kinds, many
of them may be conceived to have stolen in unseen, and to have spread
gradually over a wide area, like species migrating into new provinces.*
(* "Principles of Geology" 1st edition 1832 volume 2 chapter
11; and 9th edition page 706.)
It may now be useful to offer some remarks on the very different
reception which the twin branches of Lamarck's development theory,
namely, progression and transmutation, have met with, and to inquire
into the causes of the popularity of the one and the great unpopularity
of the other. We usually test the value of a scientific hypothesis by
the number and variety of the phenomena of which it offers a fair or
plausible explanation. If transmutation, when thus tested, has decidedly
the advantage over progression and yet is comparatively in disfavour,
we may reasonably suspect that its reception is retarded, not so much by
its own inherent demerits, as by some apprehended consequences which
it is supposed to involve and which run counter to our preconceived
opinions.
THEORY OF PROGRESSION.
In treating of this question, I shall begin with the doctrine of
progression, a concise statement of which, so far as it relates to the
animal kingdom, was thus given twelve years ago by Professor Sedgwick,
in the preface to his "Discourse on the Studies of the University of
Cambridge."
"There are traces," he says, "among the old deposits of the earth of an
organic progression among the successive forms of life. They are to
be seen in the absence of mammalia in the older, and their very
rare appearance in the newer Secondary groups; in the diffusion of
warm-blooded quadrupeds (frequently of unknown genera) in the older
Tertiary system, and in their great abundance (and frequently of known
genera) in the upper portions of the same series; and lastly, in the
recent appearance of Man on the surface of the earth."
"This historical development," continues the same author, of the forms
and functions of organic life during successive epochs, "seems to mark
a gradual evolution of creative power, manifested by a gradual ascent
towards a higher type of being." "But the elevation of the fauna of
successive periods was not made by transmutation, but by creative
additions; and it is by watching these additions that we get some
insight into Nature's true historical progress, and learn that there
was a time when Cephalopoda were the highest types of animal life, the
primates of this world; that Fishes next took the lead, then Reptiles;
and that during the secondary period they were anatomically raised far
above any forms of the reptile class now living in the world. Mammals
were added next, until Nature became what she now is, by the addition of
Man."*
(* Professor Sedgwick's "Discourse on the Studies of the
University of Cambridge" Preface to 5th edition pages 44,
154, 216, 1850.)
Although in the half century which has elapsed between the time of
Lamarck and the publication of the above summary, new discoveries have
caused geologists to assign a higher antiquity both to Man and the
oldest fossil mammalia, fish, and reptiles than formerly, yet the
generalisation, as laid down by the Woodwardian Professor, as to
progression, still holds good in all essential particulars.
The progressive theory was propounded in the following terms by the late
Hugh Miller in his "Footprints of the Creator."
"It is of itself an extraordinary fact without reference to other
considerations, that the order adopted by Cuvier in his "Animal
Kingdom," as that in which the four great classes of vertebrate animals,
when marshalled according to their rank and standing, naturally range,
should be also that in which they occur in order of time. The brain,
which bears an average proportion to the spinal cord of not more than
two to one, comes first--it is the brain of the fish; that which bears
to the spinal cord an average proportion of two and a half to one
succeeded it--it is the brain of the reptile; then came the brain
averaging as three to one--it is that of the bird. Next in succession
came the brain that averages as four to one--it is that of the mammal;
and last of all there appeared a brain that averages as twenty-three to
one--reasoning, calculating Man had come upon the scene."*
(* "Footprints of the Creator" Edinburgh 1849 page 283.)
M. Agassiz, in his "Essay on Classification," has devoted a chapter to
the "Parallelism between the Geological Succession of Animals and
Plants and their present relative Standing;" in which he has expressed a
decided opinion that within the limits of the orders of each great class
there is a coincidence between their relative rank in organisation and
the order of succession of their representatives in time.*
(* "Contributions to the Natural History of the United
States" Part 1.--Essay on Classification page 108.)
Professor Owen, in his Palaeontology, has advanced similar views, and
has remarked, in regard to the vertebrata that there is much positive
as well as negative evidence in support of the doctrine of an advance in
the scale of being, from ancient to more modern geological periods. We
observe, for example, in the Triassic, Oolitic, and Cretaceous
strata, not only an absence of placental mammalia, but the presence
of innumerable reptiles, some of large size, terrestrial and aquatic,
herbivorous and predaceous, fitted to perform the functions now
discharged by the mammalia.
The late Professor Bronn, of Heidelberg, after passing in review more
than 24,000 fossil animals and plants, which he had classified
and referred each to their geological position in his "Index
Palaeontologicus," came to the conclusion that, in the course of time,
there had been introduced into the earth more and more highly organised
types of animal and vegetable life; the modern species being, on the
whole, more specialised, i.e. having separate organs, or parts of the
body, to perform different functions, which, in the earlier periods and
in beings of simpler structure, were discharged in common by a single
part or organ.
Professor Adolphe Brongniart, in an essay published in 1849 on the
botanical classification and geological distribution of the genera of
fossil plants,* arrives at similar results as to the progress of the
vegetable world from the earliest periods to the present.
(* Tableau des Genres de Vegetaux fossiles, etc.
"Dictionnaire Universel d'Histoire Naturelle" Paris 1849.)
He does not pretend to trace an exact historical series from the
sea-weed to the fern, or from the fern again to the conifers and
cycads, and lastly from those families to the palms and oaks, but he,
nevertheless, points out that the cryptogamic forms, especially the
acrogens, predominate among the fossils of the primary formations,
the Carboniferous especially, while the gymnosperms or coniferous and
cycadeous plants abound in all the strata, from the Trias to the Wealden
inclusive; and lastly, the more highly developed angiosperms, both
monocotyledonous and dicotyledonous, do not become abundant until the
Tertiary period. It is a remarkable fact, as he justly observes,
that the angiospermous exogens, which comprise four-fifths of living
plants--a division to which all our native European trees, except the
Coniferae, belong, and which embrace all the Compositae, Leguminosae,
Umbelliferae, Cruciferae, Heaths, and so many other families--are wholly
unrepresented by any fossils hitherto discovered in the Primary and
Secondary formations from the Silurian to the Oolitic inclusive. It is
not till we arrive at the Cretaceous period that they begin to appear,
sparingly at first, and only playing a conspicuous part, together with
the palms and other endogens, in the Tertiary epoch.
When commenting on the eagerness with which the doctrine of progression
was embraced from the close of the last century to the time when I first
attempted, in 1830, to give some account of the prevailing theories in
geology, I observed that far too much reliance was commonly placed on
the received dates of the first appearances of certain orders or classes
of animals or plants, such dates being determined by the age of the
stratum in which we then happened to have discovered the earliest
memorials of such types. At that time (1830), it was taken for granted
that Man had not co-existed with the mammoth and other extinct mammalia,
yet now that we have traced back the signs of his existence to the
Pleistocene era, and may anticipate the finding of his remains on some
future day in the Pliocene period, the theory of progression is not
shaken; for we cannot expect to meet with human bones in the Miocene
formations, where all the species and nearly all the genera of mammalia
belong to types widely differing from those now living; and had some
other rational being, representing Man, then flourished, some signs
of his existence could hardly have escaped unnoticed, in the shape of
implements of stone or metal, more frequent and more durable than the
osseous remains of any of the mammalia.
In the beginning of this century it was one of the canons of the popular
geological creed that the first warm-blooded quadrupeds which had
inhabited this planet were those derived from the Eocene gypsum of
Montmartre in the suburbs of Paris, almost all of which Cuvier had shown
to belong to extinct genera. This dogma continued in force for more than
a quarter of a century, in spite of the discovery in 1818 of a marsupial
quadruped in the Stonesfield strata, a member of the Lower Oolite,
near Oxford. Some disputed the authority of Cuvier himself as to the
mammalian character of the fossil; others, the accuracy of those who had
assigned to it so ancient a place in the chronological series of rocks.
In 1832 I pointed out that the occurrence of this single fossil in
the Oolite was "fatal to the theory of successive development" as then
propounded.*
(* "Principles of Geology" 2nd edition 1 173.)
Since that period great additions have been made to our knowledge of
the existence of land quadrupeds in the olden times. We have ascertained
that, in Eocene strata older than the gypsum of Paris, no less than
four distinct sets of placental mammalia have flourished; namely, first,
those of the Headon series in the Isle of Wight, from which fourteen
species have been procured; secondly, those of the antecedent
Bagshot and Bracklesham beds, which have yielded, together with the
contemporaneous "calcaire grossier" of Paris, twenty species; thirdly,
the still older beds of Kyson, near Ipswich, and those of Herne Bay,
at the mouth of the Thames, in which seven species have been found;
and fourthly, the Woolwich and Reading beds, which have supplied ten
species.*
(* Lyell's supplement to 5th edition of "Elements" 1857.)
We can scarcely doubt that we should already have traced back the
evidence of this class of fossils much farther had not our inquiries
been arrested, first by the vast gap between the Tertiary and Secondary
formations, and then by the marine nature of the Cretaceous rocks.
The mammalia next in antiquity, of which we have any cognisance, are
those of the Upper Oolite of Purbeck, discovered between the years 1854
and 1857, and comprising no less than fourteen species, referable
to eight or nine genera; one of them, Plagiaulax, considered by Dr.
Falconer to have been a herbivorous marsupial. The whole assemblage
appear, from the joint observations of Professor Owen and Dr. Falconer,
to indicate a low grade of quadruped, probably of the marsupial type.
They were, for the most part, diminutive, the two largest not much
exceeding our common hedgehog and polecat in size.
Next anterior in age are the mammalia of the Lower Oolite of
Stonesfield, of which four species are known, also very small and
probably marsupial, with one exception, the Stereognathus ooliticus,
which, according to Professor Owen's conjecture, may have been a hoofed
quadruped and placental, though, as we have only half of the lower jaw
with teeth, and the molars are unlike any living type, such an opinion
is of course hazarded with due caution.
Still older than the above are some fossil quadrupeds of small size,
found in the Upper Trias of Stuttgart in Germany, and more lately by Mr.
C. Moore in beds of corresponding age near Frome, which are also of a
very low grade, like the living Myrmecobius of Australia. Beyond this
limit our knowledge of the highest class of vertebrata does not as
yet extend into the past, but the frequent shifting back of the old
landmarks, nearly all of them once supposed in their turn to indicate
the date of the first appearance of warm-blooded quadrupeds on this
planet, should serve as a warning to us not to consider the goal at
present reached by palaeontology as one beyond which they who come after
us are never destined to pass.
On the other hand, it may be truly said in favour of progression that
after all these discoveries the doctrine is not gainsaid, for the less
advanced marsupials precede the more perfect placental mammalia in the
order of their appearance on the earth.
If the three localities where the most ancient mammalia have been
found--Purbeck, Stonesfield, and Stuttgart--had belonged all of them to
formations of the same age, we might well have imagined so limited an
area to have been peopled exclusively with pouched quadrupeds, just
as Australia now is, while other parts of the globe were inhabited by
placentals, for Australia now supports one hundred and sixty species of
marsupials, while the rest of the continents and islands are tenanted by
about seventeen hundred species of mammalia, of which only forty-six
are marsupial, namely, the opossums of North and South America. But the
great difference of age of the strata in each of these three localities
seems to indicate the predominance throughout a vast lapse of time (from
the era of the Upper Trias to that of the Purbeck beds) of a low grade
of quadrupeds; and this persistency of similar generic and ordinal types
in Europe while the species were changing, and while the fish, reptiles,
and mollusca were undergoing vast modifications, raises a strong
presumption that there was also a vast extension in space of the same
marsupial forms during that portion of the Secondary epoch which has
been termed "the age of reptiles."
As to the class Reptilia, some of the orders which prevailed when
the Secondary rocks were formed are confessedly much higher in their
organisation than any of the same class now living. If the less perfect
ophidians, or snakes, which now abound on the earth had taken the lead
in those ancient days among the land reptiles, and the Deinosaurians
had been contemporary with Man, there can be no doubt that the
progressionist would have seized upon this fact with unfeigned
satisfaction as confirmatory of his views. Now that the order of
succession is precisely reversed, and that the age of the Iguanodon was
long anterior to that of the Eocene Palaeophis and living boa, while the
crocodile is in our own times the highest representative of its class, a
retrograde movement in this important division of the vertebrata must be
admitted. It may perhaps be accounted for by the power acquired by the
placental mammalia, when they became dominant, a power before which
the class of vertebrata next below them, as coming most directly in
competition with them, may more than any other have given way.
For no less than thirty-four years it had been a received axiom in
palaeontology that reptiles had never existed before the Permian or
Magnesian Limestone period, when at length in 1844 this supposed barrier
was thrown down, and Carboniferous reptiles, terrestrial and aquatic, of
several genera were brought to light; and discussions are now going
on as to whether some remains of an Enaliosaur (perhaps a large
Labyrinthodon) have not been detected in the coal of Nova Scotia, and
whether certain sandstones near Elgin in Scotland, containing the bones
of lacertian, crocodilian, and rhynchosaurian reptiles, may not be
referable to the "Old Red" or Devonian group. Still, no traces of this
class have yet been detected in rocks as ancient as those in which the
oldest fish have been found. [38]
As to fossil representatives of the ichthyic type, the most ancient were
not supposed before 1838 to be of a date anterior to the Coal, but they
have since been traced back, first to the Devonian, and then to the
Silurian rocks. No remains, however, of them or of any vertebrate animal
have yet been discovered in the Ordovician strata, rich as these are in
invertebrate fossils, nor in the still older Cambrian; so that we seem
authorised to conclude, though not without considerable reserve, that
the vertebrate type was extremely scarce, if not wholly wanting,
in those epochs often spoken of as "primitive," but which, if the
Development Theory be true, were probably the last of a long series of
antecedent ages in which living beings flourished.
As to the Mollusca, which afford the most unbroken series of geological
medals, the highest of that class, the Cephalopoda, abounded in
older Silurian times, comprising several hundred species of chambered
univalves. Had there been strong prepossessions against the progressive
theory, it would probably have been argued that when these cephalopods
abounded, and the siphonated gasteropods were absent, a higher order of
zoophagous mollusca discharged the functions afterwards performed by an
inferior order in the Secondary, Tertiary, and Post-Tertiary seas. But
I have never seen this view suggested as adverse to the doctrine of
progress, although much stress has been laid on the fact that the
Silurian Brachiopoda, creatures of a lower grade, formerly discharged
the functions of the existing lamellibranchiate bivalves, which are
higher in the scale.
It is said truly that the Ammonite, Orthoceras, and Nautilus of these
ancient rocks were of the tetrabranchiate division, and none of them
so highly organised as the Belemnite and other dibranchiate cephalopods
which afterwards appeared, and some of which now flourish in our seas.
Therefore, we may infer that the simplest forms of the Cephalopoda took
precedence of the more complex in time. But if we embrace this view, we
must not forget that there are living Cephalopoda, such as the Octopods,
which are devoid of any hard parts, whether external or internal, and
which could leave behind them no fossil memorials of their existence,
so that we must make a somewhat arbitrary assumption, namely, that at
a remote era, no such Dibranchiata were in being, in order to avail
ourselves of this argument in favour of progression. On the other
hand, it is true that in the Lower Cambrian not even the shell-bearing
tetrabranchiates have yet been discovered.
In regard to plants, although the generalisation above cited of M.
Adolphe Brongniart is probably true, there has been a tendency in the
advocates of progression to push the inferences deducible from known
facts, in support of their favourite dogma, somewhat beyond the limits
which the evidence justifies. Dr. Hooker observes, in his recent
"Introductory Essay to the Flora of Australia," that it is impossible
to establish a parallel between the successive appearances of vegetable
forms in time, and their complexity of structure or specialisation of
organs as represented by the successively higher groups in the natural
method of classification. He also adds that the earliest recognisable
Cryptogams are not only the highest now existing, but have more highly
differentiated vegetative organs than any subsequently appearing, and
that the dicotyledonous embryo and perfect exogenous wood, with the
highest specialised tissue known (the coniferous with glandular tissue),
preceded the monocotyledonous embryo and endogenous wood in date
of appearance on the globe--facts wholly opposed to the doctrine of
progression, and which can only be set aside on the supposition that
they are fragmentary evidence of a time farther removed from the origin
of vegetation than from the present day.*
(* "Introductory Essay to the Flora of Australia," page 31
London 1859. Published separately.) [39]
It would be an easy task to multiply objections to the theory now under
consideration; but from this I refrain, as I regard it not only as a
useful, but rather in the present state of science as an indispensable
hypothesis, and one which though destined hereafter to undergo many and
great modifications will never be overthrown.
It may be thought almost paradoxical that writers who are most in favour
of transmutation (Mr. C. Darwin and Dr. J. Hooker, for example) are
nevertheless among those who are most cautious, and one would say timid,
in their mode of espousing the doctrine of progression; while, on the
other hand, the most zealous advocates of progression are oftener than
not very vehement opponents of transmutation. We might have anticipated
a contrary leaning on the part of both, for to what does the theory
of progression point? It supposes a gradual elevation in grade of the
vertebrate type in the course of ages from the most simple ichthyic form
to that of the placental mammalia and the coming upon the stage last in
the order of time of the most anthropomorphous mammalia, followed by
the human race--this last thus appearing as an integral part of the same
continuous series of acts of development, one link in the same chain,
the crowning operation as it were of one and the same series of
manifestations of creative power. If the dangers apprehended from
transmutation arise from the too intimate connection which it tends to
establish between the human and merely animal natures, it might
have been expected that the progressive development of organisation,
instinct, and intelligence might have been unpopular, as likely to
pioneer the way for the reception of the less favoured doctrine. But the
true explanation of the seeming anomaly is this, that no one can believe
in transmutation who is not profoundly convinced that all we know in
palaeontology is as nothing compared with what we have yet to learn, and
they who regard the record as so fragmentary, and our acquaintance
with the fragments which are extant as so rudimentary, are apt to be
astounded at the confidence placed by the progressionists in data which
must be defective in the extreme. But exactly in proportion as the
completeness of the record and our knowledge of it are overrated,
in that same degree are many progressionists unconscious of the goal
towards which they are drifting. Their faith in the fullness of
the annals leads them to regard all breaks in the series of organic
existence, or in the sequence of the fossiliferous rocks, as proofs
of original chasms and leaps in the course of nature--signs of the
intermittent action of the creational force, or of catastrophes which
devastated the habitable surface. They do not doubt that there is a
continuity of plan, but they believe that it exists in the Divine mind
alone, and they are therefore without apprehension that any facts
will be discovered which would imply a material connection between the
outgoing organisms and the incoming ones.