A History of Science - v.3 (Williams)

itself over a wide area. It will follow, therefore, from the adoption of our hypothesis that the recent origin

of some species and the high antiquity of others are equally consistent with the general fact of their limited distribution, some being local because they have not existed long enough to admit of their wide dissemination; others, because circumstances in the animate or

inanimate world have occurred to restrict the range within which they may once have obtained. . . .

"If the reader should infer, from the facts laid before him, that the successive extinction of animals and plants may be part of the constant and regular course of nature, he will naturally inquire whether there are any means provided for the repair of these losses? Is it possible as a part of the economy of our system that the habitable globe should to a certain extent become depopulated, both in the ocean and on the land, or

that the variety of species should diminish until some new era arrives when a new and extraordinary effort

of creative energy is to be displayed? Or is it possible that new species can be called into being from time to time, and yet that so astonishing a phenomenon can escape the naturalist?

"In the first place, it is obviously more easy to prove that a species once numerously represented in a given district has ceased to be than that some other which

Get any book for free on: www.Abika.com

did not pre-exist had made its appearance--assuming always, for reasons before stated, that single stocks only of each animal and plant are originally created, and that individuals of new species did not suddenly start up in many different places at once.

"So imperfect has the science of natural history remained down to our own times that, within the memory

of persons now living, the numbers of known animals and plants have doubled, or even quadrupled, in many classes. New and often conspicuous species are

annually discovered in parts of the old continent long inhabited by the most civilized nations. Conscious, therefore, of the limited extent of our information, we always infer, when such discoveries are made, that the beings in question bad previously eluded our research, or had at least existed elsewhere, and only migrated at a recent period into the territories where we now find them.

"What kind of proofs, therefore, could we reasonably expect to find of the origin at a particular period of a new species?

"Perhaps, it may be said in reply, that within the last two or three centuries some forest tree or new quadruped might have been observed to appear suddenly in those parts of England or France which had

been most thoroughly investigated--that naturalists

Get any book for free on: www.Abika.com

might have been able to show that no such being inhabited any other region of the globe, and that there

was no tradition of anything similar having been

observed in the district where it had made its appearance.

"Now, although this objection may seem plausible,

yet its force will be found to depend entirely on the rate of fluctuation which we suppose to prevail in the

animal world, and on the proportions which such conspicuous subjects of the animal and vegetable kingdoms

bear to those which are less known and escape

our observation. There are perhaps more than a million species of plants and animals, exclusive of the microscopic and infusory animalcules, now inhabiting

the terraqueous globe, so that if only one of these were to become extinct annually, and one new one were to

be every year called into being, much more than a million of years might be required to bring about a complete revolution of organic life.

"I am not hazarding at present any hypothesis as to the probable rate of change, but none will deny that when the annual birth and the annual death of one

species on the globe is proposed as a mere speculation,

this, at least, is to imagine no slight degree of instability in the animate creation. If we divide the surface of

the earth into twenty regions of equal area, one of these might comprehend a space of land and water

Get any book for free on: www.Abika.com

Now the mammalia, whether terrestrial or aquatic,

bear so small a proportion to other classes of animals, forming less, perhaps, than a thousandth part of a

whole, that, if the longevity of species in the different orders were equal, a vast period must elapse before it would come to the turn of this conspicuous class to

lose one of their number. If one species only of the whole animal kingdom died out in forty years, no more than one mammifer might disappear in forty

thousand years, in a region of the dimensions of Europe.

"It is easy, therefore, to see that in a small portion of such an area, in countries, for example, of the size of England and France, periods of much greater duration must elapse before it would be possible to authenticate the first appearance of one of the larger plants or animals, assuming the annual birth and death

Get any book for free on: www.Abika.com

of one species to be the rate of vicissitude in the animal creation throughout the world."[3]

In a word, then, said Lyell, it becomes clear that the numberless species that have been exterminated in the past have died out one by one, just as individuals of a species die, not in vast shoals; if whole populations have passed away, it has been not by instantaneous extermination, but by the elimination of a species now here, now there, much as one generation succeeds another in the life history of any single species. The

causes which have brought about such gradual exterminations, and in the long lapse of ages have resulted

in rotations of population, are the same natural causes that are still in operation. Species have died out in the past as they are dying out in the present,

under influence of changed surroundings, such as altered climate, or the migration into their territory of

more masterful species. Past and present causes are one--natural law is changeless and eternal.

Such was the essence of the Huttonian doctrine, which Lyell adopted and extended, and with which his name will always be associated. Largely through his

efforts, though of course not without the aid of many other workers after a time, this idea--the doctrine of uniformitarianism, it came to be called--became the

Get any book for free on: www.Abika.com

accepted dogma of the geologic world not long after the middle of the nineteenth century. The catastrophists, after clinging madly to their phantom for a generation, at last capitulated without terms: the old heresy became the new orthodoxy, and the way was paved for a

fresh controversy.

THE ORIGIN OF SPECIES

The fresh controversy followed quite as a matter of course. For the idea of catastrophism had not concerned the destruction of species merely, but their

introduction as well. If whole faunas had been extirpated suddenly, new faunas had presumably been introduced

with equal suddenness by special creation;

but if species die out gradually, the introduction of new species may be presumed to be correspondingly gradual. Then may not the new species of a later geological

epoch be the modified lineal descendants of the extinct population of an earlier epoch?

The idea that such might be the case was not new.

It had been suggested when fossils first began to attract conspicuous attention; and such sagacious thinkers as Buffon and Kant and Goethe and Erasmus Darwin had

been disposed to accept it in the closing days of the eighteenth century. Then, in 1809, it had been contended for by one of the early workers in systematic

Get any book for free on: www.Abika.com

paleontology--Jean Baptiste Lamarck, who had studied the fossil shells about Paris while Cuvier studied the vertebrates, and who had been led by these studies to conclude that there had been not merely a rotation but a progression of life on the globe. He found the fossil shells--the fossils of invertebrates, as he himself had

christened them--in deeper strata than Cuvier's vertebrates; and he believed that there had been long ages

when no higher forms than these were in existence, and that in successive ages fishes, and then reptiles, had been the highest of animate creatures, before mammals, including man, appeared. Looking beyond the pale of

his bare facts, as genius sometimes will, he had insisted that these progressive populations had developed one

from another, under influence of changed surroundings, in unbroken series.

Of course such a thought as this was hopelessly misplaced in a generation that doubted the existence of extinct species, and hardly less so in the generation that accepted catastrophism; but it had been kept alive by here and there an advocate like Geoffrey Saint-Hilaire, and now the banishment of catastrophism opened the

way for its more respectful consideration. Respectful consideration was given it by Lyell in each recurring edition of his Principles, but such consideration led to its unqualified rejection. In its place Lyell put forward a modified hypothesis of special creation. He assumed

Get any book for free on: www.Abika.com

that from time to time, as the extirpation of a species had left room, so to speak, for a new species, such new species had been created de novo; and he supposed that such intermittent, spasmodic impulses of creation manifest themselves nowadays quite as frequently as at any

time in the past. He did not say in so many words that no one need be surprised to-day were he to see a new species of deer, for example, come up out of the

ground before him, "pawing to get free," like Milton's lion, but his theory implied as much. And that theory, let it be noted, was not the theory of Lyell alone, but of nearly all his associates in the geologic world. There is perhaps no other fact that will bring home to one so vividly the advance in thought of our own generation

as the recollection that so crude, so almost unthinkable a conception could have been the current doctrine of science less than half a century ago.

This theory of special creation, moreover, excluded

the current doctrine of uniformitarianism as night excludes day, though most thinkers of the time did not

seem to be aware of the incompatibility of the two ideas. It may be doubted whether even Lyell himself fully realized it. If he did, he saw no escape from the dilemma, for it seemed to him that the record in the

rocks clearly disproved the alternative Lamarckian hypothesis. And almost with one accord the paleontologists

of the time sustained the verdict. Owen, Agassiz, Falconer, Barrande, Pictet, Forbes, repudiated the idea

Get any book for free on: www.Abika.com

as unqualifiedly as their great predecessor Cuvier had done in the earlier generation. Some of them did, indeed, come to believe that there is evidence of a progressive development of life in the successive ages, but

no such graded series of fossils had been discovered as would give countenance to the idea that one species had ever been transformed into another. And to nearly

every one this objection seemed insuperable.

But in 1859 appeared a book which, though not dealing primarily with paleontology, yet contained a chapter that revealed the geological record in an altogether new light. The book was Charles Darwin's

Origin of Species, the chapter that wonderful citation of the "Imperfections of the Geological Record." In this epoch-making chapter Darwin shows what conditions

must prevail in any given place in order that fossils shall be formed, how unusual such conditions are, and

how probable it is that fossils once imbedded in sediment of a sea-bed will be destroyed by metamorphosis

of the rocks, or by denudation when the strata are raised above the water-level. Add to this the fact that only small territories of the earth have been explored geologically, he says, and it becomes clear that the paleontological record as we now possess it shows but a mere fragment of the past history of organisms on the earth. It is a history "imperfectly kept and written in a changing dialect. Of this history we possess the last

Get any book for free on: www.Abika.com

volume alone, relating only to two or three countries. Of this volume only here and there a short chapter has been preserved, and of each page only here and there a few lines." For a paleontologist to dogmatize from such a record would be as rash, he thinks, as "for a

naturalist to land for five minutes on a barren point of Australia and then discuss the number and range of its productions."

This citation of observations, which when once pointed out seemed almost self-evident, came as a revelation to the geological world. In the clarified view now

possible old facts took on a new meaning. It was recalled that Cuvier had been obliged to establish a new

order for some of the first fossil creatures he examined, and that Buckland had noted that the nondescript

forms were intermediate in structure between allied existing orders. More recently such intermediate forms

had been discovered over and over; so that, to name but one example, Owen had been able, with the aid of

extinct species, to "dissolve by gradations the apparently wide interval between the pig and the camel."

Owen, moreover, had been led to speak repeatedly of

the "generalized forms" of extinct animals, and Agassiz had called them "synthetic or prophetic types," these terms clearly implying "that such forms are in fact intermediate or connecting links." Darwin himself had shown some years before that the fossil animals of any continent are closely related to the existing animals

Get any book for free on: www.Abika.com