CHAPTER 20. — THEORIES OF PROGRESSION AND TRANSMUTATION.

  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.