Front Page Titles (by Subject) APPENDIX F.: REMARKS ON THE THEORY OF RECIPROCAL DEPENDENCE IN THE ANIMAL AND VEGETABLE CREATIONS AS REGARDS ITS BEARING UPON PALÆONTOLOGY. - An Autobiography, vol. 1
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APPENDIX F.: REMARKS ON THE THEORY OF RECIPROCAL DEPENDENCE IN THE ANIMAL AND VEGETABLE CREATIONS AS REGARDS ITS BEARING UPON PALÆONTOLOGY. - Herbert Spencer, An Autobiography, vol. 1 
An Autobiography by Herbert Spencer. Illustrated in Two Volumes. Vol. I (New York: D. Appleton and Company 1904).
Part of: An Autobiography
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REMARKS ON THE THEORY OF RECIPROCAL DEPENDENCE IN THE ANIMAL AND VEGETABLE CREATIONS AS REGARDS ITS BEARING UPON PALÆONTOLOGY.
[From the “Philosophical Magazine” for February, 1844.]
Upon perusing an article which some time since appeared in the “Philosophical Magazine,” explanatory of M. Dumas’ views respecting the peculiar relationship which exists between plants and animals,* in so far as their action upon the atmosphere is concerned, it occurred to me that the doctrine there set forth involved an entirely new and very beautiful explanation of the proximate causes of progressive development; and as the idea does not seem to have been yet started, perhaps I may be allowed to make your journal the medium for its publication.
In unfolding the several results of the theory and exhibiting its application in the solution of natural phenomena, M. Dumas adverts to the fact, that not only do the organisms of the vegetable kingdom decompose the carbonic acid which has been thrown into the atmosphere by animals, but that they likewise serve for the removal of those extraneous supplies of the same gas which are being continually poured into it through volcanos, calcareous springs, fissures, and other such channels. It is to the corollary deducible from this proposition, respecting the alterations that have taken place in the composition of that atmosphere, that attention is requested.
If it had been found that during the past epochs of the world’s existence, animals had always borne such a proportion to plants as to insure the combustion of the whole of the carbon assimilated by them from the air, or in other words, if the carbon-reducing class had always been exactly balanced by the carbon-consuming class, it would then follow that, as the gas decomposed in the one case was wholly recomposed in the other, the only change that could have taken place in the character of the atmosphere would have been a deterioration resulting from the continual influx of carbonic acid from the above-mentioned sources. Such, however, were not the conditions of the case; for it is manifest, not only from the nature of existing arrangements, but likewise from the records of the world’s history, that the vegetable kingdom has always had such a preponderance as to accumulate a much larger supply of carbon than could be consumed by animals. This was especially the fact in the earlier æras. During those vast periods that expired before the appearance of mammalia, and whilst animate life was chiefly confined to rivers and seas, nearly the whole of the immense masses of vegetation that then covered the land, apparently with a much more luxuriant growth than now, must have lived and died untouched by quadrupeds; and even though a certain portion of the carbon taken by them from the atmosphere was again restored to it in the process of decomposition, by far the greater bulk seems to have remained in its uncombined form. Even after the creation of the higher orders of vertebrata, when the forests were inhabited by the Mylodon with its congeners, and subsequently by the elephant and others of the Pachydermata, it cannot be supposed that there was ever by their instrumentality an equilibrium produced between those antagonist agencies—the vegetable and animal creations. For although herds of such creatures would doubtless commit extensive ravages upon the vegetation amid which they existed, it must be remembered that they could only consume the young and comparatively succulent portions of the trees upon which they fed, whilst the whole of the carbon contained in the trunks and older branches would remain untouched. That the same preponderance in the assimilative power of the vegetable organisms over the consuming power of the animal ones exists at the present day is abundantly evident.
The fact of there having been a larger abstraction of carbon from the atmosphere by the decomposition of its carbonic acid gas than has ever been returned to it, will, however, be most distinctly proved by a reference to purely geological data. The vast accumulations of carbonaceous matter contained in the numerous coal-basins distributed over the surface of the globe, the large proportion of bitumen existing in many of the secondary deposits, to say nothing of the uncombined carbon which must be diffused through a great part of the strata composing the Earth’s crust, bear palpable witness to the truth of the position. All such combustible material has been originally derived from the air, and the fact of its remaining to the present day unoxidized, and bidding fair to continue in the same condition (setting aside human agency), for an indefinite period, strongly favours the conclusion that the carbon of which it is composed has been permanently reduced from the gaseous combination in which it previously appeared.
If, then, it be conceded that the carbonic acid which, during the past æras escaped out of the Earth, has been continually undergoing the process of de-carbonization, it follows as an apparently legitimate consequence, that its remaining constituent, the oxygen, being thus constantly liberated and diffused into the atmosphere, now exists in that medium in a larger proportion than it originally did, and that it has from the commencement of vegetable life to the present day been ever on the increase.
To this inference there may, however be raised objections. It will possibly be said that the carbonic acid which in time past issued by various channels out of the Earth, arose from the slow combustion of carbonaceous deposits produced in the same way as those now existing; that the continuance of the like phenomenon in our own day is due to the gradual destruction of the same material; and that the strata of our coal-fields are fated to undergo, by some future volcanic agency, a similar revolution, and have their carbon once more sent into the air in company with oxygen. Or it might perhaps be argued that the oxygen set free by the instrumentality of plants has entered into combination with some other element in place of the carbon with which it was associated, and has thus been again abstracted from the air as fast as it was added to it.
The first of these objections is plausible, in so far as the possibility of such an arrangement is concerned, though it does not appear to be countenanced by facts. Neither the positions usually occupied by volcanos, nor the phænomena attending their eruptions, seem to indicate that the carbonic acid they evolve proceeds directly from the combustion of carbonaceous matter. They rather imply that it has been driven off from its combinations by heat or chemical affinity. In the cases of calcareous springs it would also appear that the gas liberated by them had been previously in connexion with an earth, it may be for an indeterminate period. Moreover, it should be borne in mind that the ultimate tendency of all chemical changes taking place in the interior of the globe must be to oxidize the most combustible elements; and since the greater part of the abundant metallic bases have a stronger affinity for oxygen than carbon has, its continual de-oxidation would result, rather than any action of the opposite character. But even admitting the existence of some play of affinities by which the carbonaceous matter deposited in the course of one æra is transformed into carbonic acid and given back to the atmosphere during another, there is still a link wanting to complete the chain of this circulating system; for it is clear that the oxygen which accompanies the carbon in each of its re-appearances above ground has been derived from some internal source, and when it has once issued into the air and been deprived of its carbon it has no visible means of regaining its previous condition, and must consequently remain in the air. On this assumption, therefore, we are still brought in a great degree to the same conclusion. Here, indeed, the second objection may perhaps be brought in aid of the first, and in such case it would be said that the oxygen after being liberated is again absorbed by other agencies, and ultimately carried down once more into the interior. This is, however, rather a groundless supposition: there being no apparent mode in which such process could be carried on, seeing that the surface of the Earth is already oxidized, and, as far as we can judge, has always been so.
Assuming, then, that the proposed theory, supported as it is by the fact that the constituents of the atmosphere, are not in atomic proportions, and borne out likewise by the foregoing arguments, is correct, let us mark the inferences which may be drawn respecting the effects produced upon the organic creation.
Superior orders of beings are strongly distinguished from inferior ones by the warmth of their blood. A low organization is uniformly accompanied by a low temperature, and in ascending the scale of creation we find that, setting aside partial irregularities, one of the most notable circumstances is the increase of heat. It has been further shown, by modern discoveries, that such augmentation of temperature is the direct result of a greater consumption of oxygen; and it would appear that a quick combustion of carbonaceous matter through the medium of the lungs is the one essential condition to the maintenance of that high degree of vitality and nervous energy without which exalted psychical or physical endowments cannot exist.
Coupling this circumstance with the theory of a continual increase in the amount of atmospherical oxygen, we are naturally led to the conclusion that there must of necessity have been a gradual change in the character of the animate creation. If a rapid oxidation of the blood is accompanied by a higher heat and a more perfect mental and bodily development, and if in consequence of an alteration in the composition of the air greater facilities for such oxidation are afforded, it may be reasonably inferred that there has been a corresponding advancement in the temperature and organization of the world’s inhabitants.
Now this deduction of abstract reasoning we know to be in exact accordance with geological observations. An inspection of the records of creation demonstrates that such change has taken place, and although remains have from time to time been found which prove that beings of an advanced development existed at an earlier period than was previously supposed, still the broad fact is not by any means invalidated. A retrospective view of the various phases of animal life, tracing it through the extinct orders of mammalia, saurians, fishes, crustacea, radiata, zoophytes, &c., shows distinctly that whatever may have been the oscillations and irregularities produced by incidental causes, the average aspect nevertheless indicates the law of change alluded to, seeing that there appears to have been an æra in which the Earth was occupied exclusively by cold-blooded creatures, requiring but little oxygen; that it was subsequently inhabited by animals of superior organization consuming more oxygen; and that there has since been a continual increase of the hot-blooded tribes and an apparent diminution of the cold-blooded ones.
Bearing in mind, therefore, the undoubted relationship that exists between the consumption of oxygen on the one hand and the degree of vitality and height of organization on the other, it would appear extremely probable that there is some connexion between the supposed change in the vital medium and the increased intensity of life and superiority of construction which have accompanied it. Whether the alteration that has taken place in the constitution of the atmosphere, is to be looked upon as the cause of this gradual development of organic existence, or whether it is to be regarded as an arrangement intended to prepare the Earth for the reception of more perfect creatures, are points which need not now be entered upon. The question at present to be determined is, whether the alleged improvement in the composition of the air has really happened, and, if so, whether that improvement has had anything to do with the changes that have taken place in the characteristics of the Earth’s inhabitants.
[Sundry objections may be urged against the propositions embodied in this essay, as well as against its conclusion. I reproduce it not so much because of its intrinsic value as because it illustrates, in another direction, the speculative tendency otherwise variously illustrated.]
[*]“Philosophical Magazine,” Series 3, vol. xix, p. 337.