lyell and the "reality" of species: 1830-1833

Lyell and the "Reality" of Species: 1830-1833Author(s): William ColemanSource: Isis, Vol. 53, No. 3 (Sep., 1962), pp. 325-338Published by: The University of Chicago Press on behalf of The History of Science SocietyStable URL: http://www.jstor.org/stable/227785 .

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Lyell and the "Reality" of Species:

1830 -1833

By William Coleman *

USTOMARILY the historian of science, upon mention of the name of Charles Lyell (1795-1875), will speak of those physical forces whose

regular and gradual operations, acting without change of intensity throughout immense periods of time, modify the surface of the globe, slowly eroding its mountains, gently depositing layers of sediment upon the ocean floor, and occasionally throwing up volcanoes. Yet, despite Lyell's successful

advocacy of uniformitarian geology, he was not exclusively a geologist.1 In his youth he had been an avid entomologist and, when later in life he traveled in Europe and North America, he rarely failed to record the conspicuous flora and fauna of these regions. Lyell was, in fact, an accomplished naturalist who understood that the geological series of strata and the sequence of the fossil record must be investigated as parts of the same problem, that the geographical distribution of contemporary organisms was directly related to the history of life on earth, and that resolution of the question of the "reality" of species must precede any genuine progress in biology.

This paper, which is intended to review the neglected biological contri- bution of Lyell, attempts to demonstrate the cautious assurance with which he accepted the " reality " of species and to indicate Lyell's confusion of the taxonomically distinct species with the temporally fixed species. Lyell's rejection of the transformation of species, a stand which he would publicly abandon only in the 1860's, is reviewed and his answer to the species problem presented. Finally there is a short discussion of Lyell's relationship to the work of Edward Blyth and Charles Darwin.

The second, or biological, volume (1832) of Lyell's Principles of Geology proposes to deal with the changes of the organic world, including those which are impressed upon it by external circumstances and those which the organisms themselves effect. Lyell immediately turns to the vicissitudes to which a species is subjected, and asks ". . . whether species have a real and permanent existence in nature; or whether they are capable, as some naturalists pretend, of being indefinitely modified in the course of a long

* The Johns Hopkins University. Lyell's geological views is found in C. C. 1 On the life of Lyell see Charles Lyell, Life, Gillispie, "The Uniformity of Nature," in

Letters and Journals, ed. K. Lyell, 2 vols. Genesis and Geology: A Study in the Relations (London: 1881) and E. Bailey, "Charles Lyell, of Scientific Thought, Natural Theology, and

F.R.S. (1797-1875)," Notes Roy. Soc. Lond. Social Opinion in Great Britain, 1790-1850 14: 121-138 (1959). A suggestive account of (Cambridge: 1951) 121-148.

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ISIS, 1962, VOL. 53, PART 3, No. 173.



WILLIAM COLEMAN

series of generations? " 2 If the species are not real, the obvious consequences are alarming: unlimited change becomes not only possible but even necessary. Species will no longer have well-defined limits, classification becomes a purely arbitrary exercise, and any species may easily be transformed into another. Lyell rejected this solution. He is fully aware that the only alternative to the complete constancy of species is a collapse into total transformism:

... if there once appears ground of reasonable doubt, in regard to the constancy of species, the amount of transformation which they are capable of undergoing may seem to resolve into a mere question of the quantity of time assigned to the past duration of animate existence.3

Thus, inconstancy directs that specific diversity become a function of time. An external Creator or First Cause will, by this hypothesis, become super- fluous for the continued existence and activity of organic nature and the

suggestion of pure materialism will gain further plausibility. Materialism distressed Lyell as greatly as it did many other devoutly religious men. But he was not compelled to attack the transformist doctrine on the grounds of infidelity because he already possessed what he believed were convincing scientific refutations of the theory.

In any inquiry we must completely understand the arguments of our adversaries or, Lyell suggests, " we are not warranted in assuming the con-

trary." 4 Lyell's proposition is especially applicable to the doctrine of specific transformation. The cautious quality of Lyell's mind here becomes quickly evident; his sane consideration of Lamarck's theories contrasts sharply, and

favorably, with the misleading representations of the French naturalist's work offered by other contemporary English writers.5 Although wholly unsympathetic with Lamarck's philosophy, Lyell wisely decided to refute it on its own grounds, that is, to challenge the scientific evidence brought forward in its behalf, and only then, if ever, to pass on to its more emotional

aspects, in particular, the place of man in nature. Lamarckian theory begins with the destruction of the stable species con-

cept of his contemporary naturalists. This idea appears to derive in part from an excessive concentration upon local flora and fauna. Within a circumscribed area a naturalist rarely has difficulty distinguishing the various

species collected. Individuals of a given species exhibit among themselves

many characters in common, when these are treated as a whole and are not arbitrarily selected, with their close spatial and structural relatives. When a naturalist, however, extends the range of his collecting, he finds the limits of his species becoming more uncertain. The different specimens appear to intergrade ultimately into one another; specific definition disappears.

2 Charles Lyell, Principles of Geology, being 5 See, e. g., William Kirby, On the Power, an attempt to explain the former changes of Wisdom and Goodness of God as Manifested the earth's surface by reference to causes now in the Creation of Animals and in their in operation [hereafter cited as PG], 3 vols. History Habit and Instincts, 2 vols. (London: (London: 1830-1833), ii, 1. 1835), i, xxii-xlii and [Robert Chambers]

3PG, ii, 18. Vestiges of the Natural History of Creation 4PG, ii, 3. (New York: n.d.), 118-120.

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LYELL AND THE "REALITY " OF SPECIES

Lyell summarized this discovery when characterizing the Lamarckian view-

point:

The greater the abundance of natural objects assembled together, the more do we discover proofs that everything passes by insensible shades into some- thing else; that even the most remarkable differences are evanescent, and that naturalists, for the most part, left us nothing at our disposal for establishing distinctions ...6

Lamarck's explanation of this phenomenon is well known. In proportion as the species change their habitat, climate, manner of living, etc. they experience a change in appearance, structure, and even behavior. If the

pressure of circumstances persists, they may be entirely altered and become a new species. Usually, however, the transformation is gradual, and intermediate forms will be expected to occur. The transitions, nevertheless, from one species to another, or between the relationships of several species among themselves, are not always clear. It is true that there are internal demands (" habits ") which tend to orient all organisms along a single path of

perfection running from monad to man. Lamarck, however, was too experienced a naturalist to proclaim inflexibly that this series was an order of nature. Organisms, when subjected to the actions of the environment, would

occasionally be forced to adapt themselves to the new circumstances and these controlling conditions could scarcely be assumed to restrain life to a single, advancing path. His final portrayal of the relationships of animals and of plants expanded into a complicated reticulum or network.7

Lyell pointedly quotes the concluding words of a lengthy statement by Lamarck, in which it was maintained that " habits " may effectively induce structural change in organs and organisms. It is useful to repeat this perhaps most notorious of all Lamarck's utterances - that on the induction of the

long neck of the giraffe - for it provides the basis for one of Lyell's most

devastating criticisms of the Lamarckian doctrine.

The cameleopard was not gifted with the long flexible neck because it was destined to live in the interior of Africa, where the soil was arid and devoid of herbage, but being reduced by the nature of the country to support itself on the foliage of lofty trees, it contracted a habit of stretching itself up to reach the high boughs, until its forelegs became longer than its hinder, and its neck so elongated, that it could raise its head to the height of twenty feet above the ground.8

The obvious point of attack on this example is the phrase " contracted a habit." Vague and intangible, it seems to serve no other function than to eliminate the demands of teleological reasoning. But Lyell elected to

challenge a more central point, that of the induction of novelty. Lamarck declares that new habits, forced upon the desert dwelling giraffe, have given rise to the distinctive limbs and neck of this creature. The inevitable conse-

6 PG, ii, 4. (Paris: 1926), ii, 176-199. 7 See H. Daudin, Les Classes zoologiques et 8 PG, ii, 9-10.

l'Idee de serie animale (1790-1830), 2 vols.

327



WILLIAM COLEMAN

quence of this " absurd " argument is that organic structures have arisen de novo and with no reference to the original constitution of the species.9 Lyell resolutely denies that new conditions can provoke the appearance of new structures and declares that there has never been the least evidence that such alterations have ever taken place. His words are unequivocal:

. . no positive fact is cited to exemplify the substitution of some entirely new sense, faculty, or organ in the room of some other suppressed as use- less .... We must point out to the reader this important chasm in the chain of evidence, because he might otherwise imagine that we had merely omitted the illustrations for the sake of brevity, but the plain truth is, that there were no examples to be found. . .10

By violating the "strict rules of induction" Lamarck has given us only " names for things." He has not discovered the source of biological novelty, but has only shown how use or disuse may modify, sometimes to an extra-

ordinary degree, pre-existing structures. An arid climate might have induced the elongation, but certainly not the origination, of the giraffe's neck. In- creased use or disuse could only lead to its augmentation or obliteration, but never to its creation.

Naturalists accompanying the Napoleonic Egyptian Expedition (1798- 1799) had sent to Paris great numbers of mummified specimens collected in the tombs and burial grounds along the Nile. It was already known that

comparison of human remains taken from Egypt, dating from circa 3000- 2000 B. C., with examples of modern European man established their con-

specificity. But would the lower animals of ancient Egypt, the cat, dog, ox, crocodile, etc., the collection of whose remains had been a major objective of the naturalists on the Expedition, also be essentially similar to modern

representatives? The fact that they were similar was accepted by many as

furnishing strong evidence against the transformation of species. Lyell joins Cuvier in declaring that five thousand years certainly should be sufficient, if the species were as pliable as Lamarck maintained, to induce at least minor but discernible modifications.ll Lamarck's reply to this interpretation - he

suggested that the dry, even climate of Egypt had not appreciably changed during these many centuries and, hence, there could have been no changed environmental conditions which would alter the species - was countered

by Lyell who noted that, despite transportation throughout the globe by man and other means, the cat had remained a cat and the ox an ox. Domestic dogs, having run wild on West Indian islands, nevertheless pro- duced whelps which responded immediately and completely to the taming action of man.l2 Even horticultural varieties are limited and are usually dependent upon care by man who provides the necessary protection for their success. That these varieties cannot maintain their integrity when man's surveillance is absent is the implied objection.3

The first impression of the Philosophie zoologique of Lamarck was the

9 PG, ii, 9. 12 PG, ii, 26-27. 10 PG, ii, 8. 13 PG, ii, 31-35. 1 PG, ii, 28-31.

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LYELL AND THE "REALITY" OF SPECIES

primary source of Lyell's information concerning transformism. In this work, published in 1809, Lamarck adhered quite strongly to the notion of a unique, linear scale of organic perfection. The conspicuous gaps or incon- sistencies in the sequence could be explained on the basis of the secondary action of the environment. In 1815, however, Lamarck, in his Histoire naturelle des animaux sans vertebres, recognized the inadequacies of this

representation and substituted for it a complex of several intertwining series.14 There is no evidence, however, that Lyell was aware of this pro- found change of viewpoint.15

A major aim of the Principles of Geology was to destroy totally the theory of the successive development of organic creation. Lamarck's progression was attacked on two grounds. Firstly, a single, linear sequence could in no

way accurately embrace the confused multiplicitly of existing organisms. Lyell does not explicitly develop this criticism; it only becomes apparent when one follows his analysis of the problem of geographical distribution and the concrete nature of the species definition.16 Lamarck's hypothesis, nevertheless, was easily shattered, Lyell believed, by paleontological evidence. Lyell states that the " theory of progressive development of organic life, from the simplest to the most complicated forms," derives absolutely no support from the fossil record.17 Organisms, this record discloses, appear neither successively, ascending from plants to animals, nor progressively, in which their occurrence would be oriented towards the production of man. Representatives of all the major biological phyla have at all times been present, somewhere at least upon the earth. In the primitive rocks, among the 200-300 known fossil species of plants, there occur a few dicotyledonous specimens but ". . . these exceptions are as fatal to the doctrine of successive development as if there were a thousand ... 18 Fish, reptiles, and testacea are similarly found in the earliest fossiliferous deposits known at that time. The absence of birds and mammals is due to the difficulty and consequent rarity of their fossilization.19 The Secondary rocks contain all but the highest mammalia and the Tertiary London clay strata even inverts the supposed order: fish and reptiles, but no mammals, are present.20 Lyell's conservative position recognizes that, although change and extinction are seemingly omnipresent, definite organic forms have been able to survive and doubtlessly will continue to exist in the future:

. . .even in the oldest rocks which contain organic remains, some genera of marine animals are recognized, of which species still exist in our seas, and these are repeated at different intervals in all the intermediate groups of strata, attesting that, amidst the variety of revolutions of which the earth's surface has been the theatre, there has never been a departure from the conditions necessary for the existence of certain unaltered types of organisation.21

14 See above, n. 7. 18 PG, i, 169. This argument may be based 15 Lyell's acquaintance with Lamarck's ideas on faulty evidence: dicotyledonous plants have

appears to have begun only in late 1826 or not appeared in what Lyell called the primi- 1827 and was confined to the Philosophie tive rocks.

zoologique. Lyell, Life, Letters and Journals, 19 PG, i, 171.

i, 168. 20 PG, i, 175. 16 See below, pp. 332-336. 21 PG, i, 185. 17 PG, i, 167.

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WILLIAM COLEMAN

Unfortunately, Lyell's interpretation of his facts was inadequate. Certain "types of organisation" have been able to survive throughout extraordinarily long geological periods. This is true, however, for only a very small number of organisms. As knowledge of the fossil record accumulated, it became increasingly evident that organisms had appeared sequentially. Even today there are very few wholly satisfactory fossil histories of individual species but there is indubitable evidence that the major phyla and classes, especially those of the vertebrates, did not arise simultaneously.22

The paleontological data which Lyell possessed, while accurate, were quite certainly hopelessly incomplete. Paleontology, as a rigorous discipline, was in 1832 scarcely two decades old, having emerged from the work of the Paris naturalists of the First Empire. Lyell could not be expected to detect long term trends in the fossil remains on the basis of this material. He knew well the great difficulties which attended fossilization and the persistence in the rocks of formed fossils. Yet he did not realize that the fossil record as it then was known - from the middle Palaeozooic - actually represented an age whose beginning had already witnessed the appearance of the vertebrates and had been preceded by a period of almost equal length during which the greatest part of the invertebrate fauna had appeared.23 Like Cuvier, his attention was necessarily arrested by the individual specimens and the differences which characterized them.

Not only did the paleontological record destroy the vision of a successive

development of animals but it further nullified any pretentions of progressionism. The recent appearance of man on earth might superficially seem to support the progressionist idea. Lyell reflects that:

The recent origin of man, and the absence of all signs of any rational being holding an analogous relation to former states of the animate world, affords one, and the only reasonable argument, in support of the hypothesis of a progressive scheme, but none whatever in favour of the fancied evolution of one species out of another.24

Of man's recent origin there could be no question. No one would deny it, Lyell admits, and the only problem is to trace sufficiently man's antiquity in order to relate his appearance to that of the recent animals.25 This conclusion is based on " grounds which may be termed strictly geological "; there is no geological (or archeological) evidence of the existence of ancient man.26 Lyell had, naturally enough, anticipated these results. Man, in his

opinion, is wholly set apart from the remainder of creation by the possession of reason and thus, even if a successive development of all other organisms could be demonstrated, which of course it cannot, man, a moral creature, would remain distinct and unaffected. Lyell declares that ". . . the superiority of man depends not on those faculties and attributes which he shares in

22 That is, they have not all existed for the Meaning of Evolution (New Haven: 1949), 12. same length of time and they have not ap- 24 PG, ii, 60. Note, incidentally, Lyell's use

peared in a single series, deriving one from of the term "evolution" in a modern sense. the other. 25 pG, i, 177.

23 See, e. g., the chronology of geological 26 PG, ii, 270. strata as presented in G. G. Simpson, The

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LYELL AND THE " REALITY" OF SPECIES

common with the inferior animals, but on his reason, by which he is distinguished from them." 27 Even the facts adduced in favor of progression are erroneous: there is neither a sequence of development from the animals to man nor a similar one among the races of man. The presumed increase in sagacity, as anatomically indicated by the facial angle, supposedly in- creasing among the races of men, indicates nothing according to Lyell; the facts offered in its support are both contradictory and irrelevant. Similarly, progression of adult forms, based on an illegitimate analogy with

embryological development (Tiedemann and Serres are cited), must be disallowed.28 By dissociating man from other organisms, Lyell retained his

unique status in the Creation and freed him from total dependance upon natural forces. Conversely, man could no longer be considered a model towards which lower organisms would tend. Man's isolation at once preserved his dignity and rendered meaningless the supposed progressive tendency of nature.

The succession-progression reasoning implies unlimited variability of species and is therefore irreconcilable with the idea of the reality of species. After only one or a few generations, variants which arose would perhaps pass unnoticed but, given many generations, all specific identity might be lost. Transformation of a species would take place and genuine novelty would be introduced. How could this occur? Lyell has shown that Lamarck possessed no solution to this problem. Previously, for want of a plausible mechanism of change, Lyell had denied transformism. This denial, of course, conveniently and necessarily reinforced conclusions already reached by at- tacking progressionism. Then there had been no evidence that specific change was presently occurring; now there was proof that it had not occurred in the past.

Some naturalists had suggested that successful hybridization experiments convincingly demonstrated the instability of species. Lyell cites, among others, the crossing of two Nicotiana species, effected by Kolreuter, as a representative example of this work.29 Kolreuter had fertilized N. rustica with N. paniculata pollen; the hybrid plant, and all subsequent generations, were then fertilized exclusively with the same pollen. The final plant ob- tained closely resembled N. paniculata; Lyell agrees that Kolreuter had "actually changed the Nicotiana rustica into the Nicotiana paniculata." 30

Lyell's faith in the stable species, nevertheless, was not shaken by this or any similar breeding experiment. Hybridization, no more than environmental conditions, could generate new structures; it could only reshuffle or exclude characteristics already existing in the parents.31 His uncom- promising criticism goes to the length of implying that viable, fertile hybrids are not the offspring of interspecific crosses, but are actually the product of related races of the same species:

27 PG, i, 178-179. existence, the right of the strong eventually 28 PG, ii, 60-64. prevails; and the strength and durability of a 29PG, ii, 52-53. race depend mainly on its prolificness, in 30 PG, ii, 52. which hybrids are acknowledged to be weak." 31 Hybrids are, in addition, inherently weak. PG, ii, 56.

Lyell says: "In the universal struggle for

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WILLIAM COLEMAN

In general, the success attending the production and perpetuity of hybrids among plants, depends, as in the animal kingdom, on the degree of proximity between the species intermarried. If their organisation be very remote, impregnation never takes place; if somewhat less distant, seeds are formed, but always imperfect and sterile. The next degree of relationship yields hybrid seedlings, but these are barren; and it is only when the parent species are very nearly allied, that the hybrid race may be perpetuated for several generations.32

There is, in addition, a pronounced sexual aversion between members of unrelated species because of which interspecific crossing is exceedingly uncommon in nature. Hybrids from completed crosses are also infrequent and no evidence of their successful, continued procreation exists. Even in fertile hybrids, which can arise only from closely related parents, the fol- lowing generations ultimately lose their reproductive powers and the variant strain vanishes.33

Lyell was confident that his analysis had removed all foundation from the arguments of the transformists. The absence of an evolutionary mechanism, denial of the successive appearance of organisms, and the inability of hybrids to generate new organs all supported the view that the species was a discrete and unvarying unit. Lyell concludes his critique of the idea of mutable species by remarking that:

From the above considerations, it appears that the species have a real existence in nature, and that each was endowed, at the time of its creation, with the attributes and organisation by which it is now distinguished.34

The foregoing discussion displays the deficiencies in the data which

allegedly proved the transformation of species. There is, however, additional and positive evidence to suggest that the species are naturally distinct and immutable. Lyell attributes to Buffon the discovery of the " general law " of distribution, "namely, the limitation of groups of distinct species to

regions separated from the rest of the globe by certain natural barriers." 35 One might reasonably have expected to find the same plants and animals in all locations possessing similar climate and external conditions, that is, areas under the same latitude. Buffon's rule, however, rested upon the unques- tionable differences which distinguished the quadrupeds of the newly discovered American continents from those known in the Old World. Addi- tional perplexity was caused by the fact that the differences were primarily at the species level; generic relationships were usually present.

Only a few lines are needed to indicate the breadth and detail of Lyell's knowledge of the facts of animal and plant geography.36 On the continent of Eurasia, different species complexes of the same genus of plants are found in China, near the Black Sea, along the Mediterranean coasts, and on the Siberean uplands. Intermediate forms seem to be nonexistent; each species

32 PG, ii, 53. 35 PG, ii, 87. 33PG, ii, 59. 36 Further details will be found in chapters 34 PG, ii, 65. 5, 6, and 7 of PG, ii.

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LYELL AND THE " REALITY " OF SPECIES

group has special adaptations to its individual environment. The distinctness of species depends upon the effectiveness of isolating barriers. In the boreal region, for example, where sea gaps are narrow and often frozen, similar species may be traced along the northern rim of the continents entirely about the globe.37 The same relations obtain among animals, different but similar species of which are usually isolated from one another by an intervening ocean, mountain chain, broad river, desert, or other im- passible boundary.38 Some birds, for example, "are so local, that in the same archipelago, a single island frequently contains a species found in no other spot on the whole earth...." 39 Ostensible objections to the Buffonian rule cannot invalidate the general law since " natural explanations " of their origin are available. Windblown seed, capricious sea-drifting, and conscious or unconscious introduction by man can all account for the aberrations in the pattern.

Local distribution is therefore the order of nature. Each species has a sharply circumscribed territory which it must occupy and from which it may depart only upon penalty of extinction. According to Lamarck, the more widely the naturalist ranged the more indistinct he found the species boundaries to become; Lyell's doctrine, to the contrary, revealed that the widely-ranging naturalist discovered only additional distinct species, each absolutely marked off by structure, behavior, etc., from its neighbors.

Once the species definition had been thus clarified, Lyell's problem was reduced to finding a satisfactory theory which might explain both the dis- similarities and the relationships of the species. He found his answer in the familiar doctrine of special creation. The present distribution and number of species on the earth are the direct result of successive, special creations of primitive pairs of each species, each couple being at first confined to a limited area and becoming later the subject of a varying degree of dispersal. Lyell advisedly presented these views in the form of hypotheses:

Each species may have had its origin in a single pair, or individual, where an individual was sufficient, and species may have been created in succession at such times and in such places as to enable them to multiply and endure for an appointed period.40 Now this congregating, in a small space, of many peculiar species, would give an appearance of centres or foci of creation, as they have been termed, as if there were favourite points where the creative energy has been in greater action than in others, and where the numbers of peculiar organic beings have consequently become more considerable.41

No one would question the purely hypothetical nature of these propositions; the tentative manner of their phrasing sufficiently indicates Lyell's own reluctance to urge their unqualified acceptance. But, assuming an efficient Intelligence or Creator, as Lyell did, their explanatory value is obvious.

37PG, ii, 69-70. later by Darwin. 38 PG, ii, 88-91. 40 PG, ii, 124. 39PG, ii, 100. There is no reference here 41 PG, ii, 126.

to the Galapagos Islands, visited two years

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WILLIAM COLEMAN

The Design of nature, whose justification may be quite beyond human

comprehension, demands that each species receive the special attention which will endow it, at its creation, with every instrument or capacity which may ensure its fruitful existence. Lyell nevertheless intended the hypothesis as

only an introduction to a solution of the species problem. Creation of organisms was one aspect of the problem; the dispersal and ultimate distribution of the species was another and much more complicated side of the issue.

Geology, said Lyell, was the "science which investigates the successive changes that have taken place in the organic and inorganic kingdoms of nature." 42 The present distribution of a species acquires meaning only when the sum of the past experiences of that species is investigated and understood; these experiences are necessarily determined by the ecological relationships which the species has maintained. For, if the Author of Nature "had not ordained that the fluctuations of the animate and inanimate creation should be in perfect harmony with each other, it is evident that considerable spaces, now the most habitable on the globe, would soon be as devoid of life as are the Alpine snows, or the dark abysses of the ocean, or the moving sands of the Sahara." 43 The action of the environment on the distribution of organisms may be illustrated by the behavior of sea, land and river. Sediment dropped by a slowly flowing stream may drive out deep-dwelling organisms, but it simultaneously builds a new surface for other creatures which require greater heat and light. The sea attacks steep cliffs, undermining and casting them into the surf, but their debris in turn becomes the habitat of numerous littoral organisms. Vegetation springs alike from cooled volcanic flow and a newly formed coral atoll.44 Natural forces do destroy the homes and ranges of innumerable organisms, but, paralleling this ceaseless destruction, new territories are being created, areas into which surviving species may migrate or be transported, and where they may again proliferate their kind.

Because of the close interaction of the species and their environment, a slight change in the latter may provoke a significant change in the range of the former. If, supposes Lyell, an earthquake, a perfectly " natural "

geological force, were to lower the land level between the Sea of Azov and the Caspian Sea by only a " trifling amount," salt water would pour into the south Asian depression and would effect a genuine "revolution" in the flora and fauna of the area.45 Similarly, a slight elevation of the bottom shelf extending across the Strait of Gibraltar or a volcanic interruption or diversion of the flow of the Gulf Stream would extraordinarily revolu- tionize the populations of the Mediterranean basin and of the North Atlantic Ocean and northern Europe, respectively.46 The result of these physical

42 PG, i, 1. time experienced by the animate world. But 43 PG, ii, 159. these changes were always due to agents pre- 44 PG, ii, 158-159. serving the "strictest uniformity of energy," 45 PG, ii, 162-163. Lyell's way of saying that physical causes were 46 Lyell deliberately retained the term " revo- regular and knew no exceptions (PG, ii, 165);

lution" by which could be concisely sum- cataclysms were apparent only and were sug- marized the remarkable changes from time to gested only because of ignorance of previous

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LYELL AND THE " REALITY " OF SPECIES

changes will be the extinction and/or redistribution of the indigenous species. Invasion of the disturbed areas by species from adjoining territories, which would replace the annihilated groups, in some cases would serve to

explain the new pattern of distribution; in other cases, however, purely biological forces may determine this pattern. The increase in numbers of a particular species and the resulting competition for resources between this species and others found in the area may account for much specific extinction. Lyell relies heavily upon the argument of competition, saying:

. . the possibility of the existence of a certain species in a given locality, or of its thriving more or less therein, is determined not merely by tempera- ture, humidity, soil, elevation, or other circumstances of the like kind, but also by the existence or non-existence, the abundance or scarcity, of a particular assemblage of other plants and animals in the same region. If we show that both classes of circumstances, whether relating to the animate or inanimate creation, are perpetually changing, it will follow that the species are subject to incessant vicissitudes; and if the result of these mutations, in the course of ages, be so great as materially to affect the general condition of stations, it will follow that the successive destruction of species must now be a part of the regular and constant order of nature.47

Long before new circumstances could effectively produce the alterations of structure which the original occupants of an area would require for their survival, previously existing species, living perhaps on the margin of the

region which now possesses new environmental conditions, would invade and seize the newly available ecological opportunities. As a country pond or lake slowly fills with vegetation and becomes a marsh, the original lake fauna perishes because the aquatic species cannot adjust rapidly enough to the new conditions and fall victim to the competitively better marsh

plants. In the further transformation of the marsh to meadow, the marsh species must perish due to the pressure of better adapted meadow organisms.48 It is only under changed or changing ecological conditions, however, that competition will lead to great alterations of animal or plant distribution. In a stable environment, the resident species will have an overwhelm-

ingly great advantage over the invader. " Pre-occupancy," that is, monopoli- zation by a vigorous species of the resources of a given area, is the most

"powerful barrier to emigration " and prevents a random scattering and establishment of organisms.49

It must be emphasized that Lyell's conception of the competitive struggle of species is significantly unlike that which Darwin would later associate with natural selection. The competition of species, or of individuals of the same species, leads, according to Darwinian theory, to the destruction of weak, inflexible, or otherwise poorly endowed individuals and to the preservation of their better equipped relatives. Natural selection, acting upon individuals which are varying, may lead to the generation of new structures

conditions and present causes. Cf. W. F. 47PG, ii, 141. Cannon, "The Uniformitarian-Catastrophist 48 PG, ii, 174. Debate," Isis, 51: 38-55 (1960) . 49 PG, ii, 167.

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WILLIAM COLEMAN

and new species. Lyellian competition, in contrast, is a "conservative mechanism" 50 whose action leads only to the extinction or numerical reduction of a species. Its action, as conceived by Lyell, cannot in any manner entail the production of new parts or species. The creation or

origination of the latter, in Lyell's public opinion, remains the exclusive

prerogative of the Author of Nature. The significance of Lyell's study of dispersal and competition belongs to

the fundamental assumption which, unstated and concealed, animated his

analysis. It was implicit in Lyell's system that the present distribution of

plants and animals was the product of time and must therefore be studied

historically; a naturalist must consider the "vicissitudes of the species." Raw, created material (species), prompted or fettered by " natural " forces

(environmental conditions, competition), in the course of ages is distributed about the earth with apparent abandon. But the suggestion by Buffon, Prichard, and others of definite rules governing the geographical limits of

species disclosed that much which had been regarded as incoherent and the result of divine caprice really reflected human ignorance. Lyell then at-

tempted to resolve the confusions of distribution by relating them to their

determining causes, the powers of dispersal, the unequal struggle for existence, and the geological forces which altered the environment. It is clear, of course, from what has been said above, that these factors may affect only distribution and contribute nothing to the formation of new species. In the Principles of Geology the species problem became inseparable from the

study of ecology and a knowledge of geological history, and the naturalist had to recognize that species in the field, each seemingly adapted to its

neighbor and habitat, the whole forming a harmonious and stable mosaic, were subjected to a multitude of varying pressures, some new and others old, but all contributing to obscure the original, created patterns. Hence, only by interpreting the geographical distribution of species in terms of the forces acting upon organisms, and by assuming that past forces were

strictly analogous to those of the present, could a satisfactory solution of the mystery of local, distinct species be attained.

In the introduction to a recent discussion of the species problem, Mayr remarked:

One of the minor tragedies in the history of biology has been the assumption during the hundred and fifty years after Linnaeus that constancy and clear definition of species are strictly correlated and that one must make a choice of either believing in evolution (the "inconstancy" of species) and then having to deny the existence of species except as purely subjective, arbitrary figments of the imagination, or, as most early naturalists have done, believing in the sharp delimitation of species but thinking that this necessitated denying evolution.51

50 The phrase is taken from L. C. Eiseley, 51 Ernst Mayr, "Species Concepts and Defi- "Charles Darwin, Edward Blyth, and the nitions," in The Species Problem, ed. E. Mayr Theory of Natural Selection," Proc. Amer. (Washington: 1957), 2. Phil. Soc., 103: 94-158 (1959), 107.

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LYELL AND THE " REALITY" OF SPECIES

Although one might question whether his " choice " was a conscious one or not, Lyell certainly belonged to the school of "early naturalists." The ambiguities of Lyell's phrase " reality of species " are due to his failure to separate these two aspects of the question. On the one hand, the " real" species, varying within narrow and rigid limits, is the very antithesis of the plastic, transmutable Lamarckian species; on the other hand there is the "real" species of the Lyellian naturalist, morphologically unique and geo- graphically distinct and, again, wholly unlike the species as understood by the transmutationists. Lyell and his contemporaries did not realize that specific identity could be preserved even while the species was changing or that taxonomic distinctness, although usually not preserved over an indefinite lapse of time, nevertheless would be able to characterize a species in tran- sition.

Judged from a post-Darwinian point of view, Lyell's answer to the species problem is cautious, conservative, and negative. All evidence seemed to indicate that species were "real" in nature, preserving their anatomical singularity and taxonomic definition. Geology had discredited the notion of previous transmutations of species and no demonstrable mechanism for the origination and preservation of biological novelty had yet been introduced. It thus appears not unnatural that later transmutationists such as Darwin could not call upon the imposing authority of Lyell to provide support for the new doctrine of evolution by natural selection.52

Must it, then, be concluded that Lyell's thoughts on natural history were of minor or no importance? Certainly not, can be the only reply. Lyell's greatest achievement in natural history, we suggest, was to ask and to ask profoundly the species question - is the species real in nature? - and, above all, to have stated it in biological terms, opening fresh paths of inquiry and drawing together older means of investigation. Foremost among the new areas of study advocated by Lyell was the geographical distribution of organisms. The step from grasping the geographical and geological history of a species to discovering the genetic history of that species was too great for Lyell to complete; it remained for Darwin to make the necessary correla- tion. But Lyell pointed to the significance of animal and plant geography and, with abundant illustration, linked distribution to the species problem. Henceforth, a philosophic naturalist would have to interrogate simultaneously the geography, ecology, and geological past of a species.

It should now be clear that the significance of the biological discussion in the Principles of Geology lay in the combination of previously separate disciplines and the demonstration of the close bond between geology- paleontology and natural history. No less clear is the wide audience which Lyell's book reached: five editions appeared during the 1830's; four more were published prior to 1859; the great tenth edition, containing Lyell's adoption of organic evolution, was issued in 1866-1868; and an eleventh edition appeared shortly before the author's death. Further, A. R. Wallace,

52 This point is made in L. C. Eiseley, 182 n. 17. Darwin's Century (Garden City, N. Y.: 1958),

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WILLIAM COLEMAN

in the Far East, maintained correspondence with Lyell, and Darwin, immediately upon the return of the Beagle (aboard which had been the first edition of the Principles), was immediately and intimately received by the geologist. Other naturalists also studied Lyell's works, among them Edward

Blyth.53 Blyth's essays (1835-1837) reveal surprising parallels to Lyell's doc- trines; one notes, especially, striking similarity of thought on two important questions. Blyth was impressed by the ecological relations of organisms, the natural station of an isolated species and the harmonious relations of many species together. Peculiar locations are occupied by peculiar organisms; animals are "... merely beings of locality....54 As we have seen, a major portion of Lyell's inquiry is devoted to the elucidation of the meaning of ecological relationships for the " reality " of species. Blyth also, even more than Lyell, worked out the details of the struggle for existence by displaying the preservative force of selection which acts to maintain the stability of the species created by Providence. Selection, Blyth suggests, is one of the causes which ". .. tend to limit the geographical range of species, and to maintain their pristine characters without blemish or decay to their remotest posterity."

55 These resemblances between the views of Blyth and Lyell, and many similar ones for which space for discussion is not available, permit the speculation that, just as Darwin may have drawn heavily upon Blyth's ideas, so might Blyth have found inspiration and support in the Principles of Geology.56 Perhaps Darwin himself gained his first acquaintance with the principle of selection, although not, of course, selection as a creative process, from reading Lyell and found in Blyth only a detailed restatement of already familiar ideas.57

53 See above, note 50. Edward Blyth (1810- 1873) was a self-taught naturalist of great potential who, in poor health and relative poverty, went to India to become Curator at the Royal Asiatic Society of Bengal. His papers on selection were published in The Magazine of Natural History, a well-known journal received by Darwin in South America.

54 Ibid., 143. 55 Ibid., 142. 56 At one point Blyth refers directly to

Lyell: "... some sound and excellent remarks on varieties will also be found in the second volume of Lyell's Principles of Geology." Ibid., 119.

57 Eiseley's study of Blyth, although it pre- sents Blyth's work as a mature system without

reference to its sources and intellectual milieu, suggests the rewards of this approach. Lyell deserves the same consideration. The aim of this introductory essay has been to represent fairly the breadth and insight with which Lyell, in his early work of the 1830's, considered the "reality of species"; it has not attempted to enter directly the current of the great quest for the precursors of Darwin. Genuine progress in the latter awaits a comprehensive study of the Darwin manuscripts, annotations, and correspondence, on which see the very brief but tempting remarks on Darwin's annotations of Lyell's Principles, ii, in S. Smith, "The Origin of the 'Origin,'" The Advance of Sci- ence 16: 391-401 (1960).

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lyell and the "reality" of species: 1830-1833

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