CHAPTER VIII

MECHANISM AND LIFE

RECAPITULATORY.--We have already observed the mechanical theory, in the hands of Descartes, expanding itself to cover organisms and the phenomena of life, and in La Mettrie's _L'Homme Machine_, reducing even human beings to the status of automata. These theories were, however, known to be insecurely based upon somewhat hasty generalisations, for, in point of fact, the science of biology was as yet in its infancy; the _data_ for a complete vindication of the mechanical position were as yet wanting.

ADVANCE OF BIOLOGY.--Biological science, however, during the first half of the nineteenth century made considerable advances, and research continually kept bringing to light facts which seemed to substantiate the brilliant, if premature, hypothesis of Descartes. It will not be necessary for us to do more than take hasty note of certain important developments.

It was in 1828 that the German chemist Whoeler (1800-1882) for the first time in biological history prepared an organic compound (urea) from inorganic materials--an achievement universally recognised to be of the utmost significance. As a distinguished historian of the science of chemistry puts it:

"This discovery destroyed the difference which was then considered to exist between organic and inorganic bodies, viz. that the former could only be formed under the influence of vegetable or animal vital forces, whereas the latter could be artificially produced."[32]

Ten years later another German, Schleider (1804-1881) propounded the cellular theory of the structure and growth of plants, a theory which was soon extended to animal organisms by Schwann (1810-1882). The publication of this famous theory was described by a contemporary as "a burst of daylight"; it indeed illuminated what had hitherto been buried in mystery and mythology--the structure and method of growth of plants and animals. It seemed to render superfluous any form of the old conception of a "vital force" to explain the phenomena of growth, if it could now be assumed that the cells automatically absorbed outside material, increased in number by the division of individuals, and built up the organism by continual repetition of this process.

Schwann was also responsible for initiating a number of minute physiological investigations which led to a far more intimate knowledge of the action of nerves and muscles, and interpreted these in mechanical terms. "Investigations which were carried on with all the resources of modern physics regarding the phenomena of animal movements, gradually substituted for the miracles of the 'vital forces' a molecular mechanism, complicated, indeed, and likely to baffle our efforts for a long time to come, but intelligible, nevertheless, as a mechanism."[33]

Subsequent researches, notably of Helmholtz (1821-1895) and Meyer, lent strong support to this interpretation. The conception of the conservation of energy (an important axiom of the mechanical theory) was successfully applied by them to the economy of organisms. The organism was found not to _create_ energy, but only to contain remarkably efficient means of deriving it from materials absorbed as food. Thus animal warmth and the power of motion are originally "sunlight transformed in the organism of the plant," and afterwards appropriated by the animal. The power with which we move our limbs is as much the product of combustion as is the power of a steam engine, the only difference being that the organism is, of the two, the more efficient converter of energy.

THE MECHANICAL THEORY SUBSTANTIATED.--Thus, whether biologists were considering the _structure_ or the _behaviour_ of organisms, they were arriving at the same conclusions. The structure was revealed as physical and chemical structure, and the behaviour as the resultant of familiar physical and chemical processes. Hence biology came to be regarded as a compartment of physics and chemistry, for life itself was nothing but a complex physical or chemical phenomenon. Life could thus be satisfactorily expressed in terms of matter and energy. The speculations of Descartes seemed to be established by experimental science.

THE FINAL OBSTACLE.--The situation, already satisfactory to those whose hope it was to see the mechanical theory impregnably established, was marred, however, by one untoward circumstance. The phenomena of organic structure, growth, and behaviour having been reduced to order, and expressed in terms of physics and chemistry, certain important facts still resisted explanation, and stood out as a last stronghold of the older view.

THE ORIGIN OF SPECIES.--The existence of definite forms of animal and vegetable life, whose infinite variety and complexity was continually being increased by research[34]--still remained a mystery. How did these innumerable species naturally and automatically come into being? was the question that must be satisfactorily answered before the mechanical view could be held to cover all the facts.

The direction in which to look for a reply had been indicated by a number of thinkers. The French naturalist Buffon, the philosopher Kant, and the poet Goethe--besides other thinkers--had already in the eighteenth century familiarised the idea that species are not immutable, but that, by some means or other, new forms of life are derived from pre-existing ones. The conception had gained a firm foothold in England, where it was hospitably entertained by Mr. Herbert Spencer, and where it formed the staple of a book which caused a good deal of controversy in its day, and which is not yet forgotten.[35]

LAMARCK.--The evolutionary idea, however, though attractive to philosophers, and even to men of science, was insufficient as an explanation of the origin of species so long as the processes of transformation remained obscure. Naturalists could not accept an hypothesis for which there seemed to be such imperfect evidence. An ingenious French scientist, J. Baptiste de Lamarck (1744-1829) had indeed, in 1809, propounded the theory--ever since known by his name--that the use or disuse of particular organs might, after a long series of generations, result in the formation of new species. (The ideas denoted by the words "environment," "adaptation," "acquired habits"--now so familiar--may be said to have been introduced by him). But the scientific prejudices of the time were against Lamarck's theories, and he had to lament their inhospitable reception. Indeed Lamarck's critics did not hesitate to exercise their powers of ridicule, or to make fun of the giraffe who derived his long neck from the attempts of his ancestors to browse on high trees. Darwin himself talks of "Lamarck's nonsense," and of his "veritable rubbish"--language, however, which he was subsequently able to retract.

THE NEW GEOLOGY.--Perhaps the most stubborn obstacle which Lamarckian theories had to meet was the current prejudice as to the age (or youth) of the earth. Contemporary geologists were by no means prepared to grant Lamarck the illimitable periods of time which his transformation processes seemed to require. Consequently it is not surprising that the new theories, perhaps for the first time, received a measure of justice at the hands of one who himself became responsible for a revolution in the science of geology.

"I devoured Lamarck _en voyage_," writes Charles Lyell, describing a journey from Oxford in 1827. "His theories delighted me more than any novel I ever read, and much in the same way, for they address themselves to the imagination.... That the earth is quite as old as he supposes, has long been my creed."[36]

In spite of the fascination of these theories, however, Lyell was not carried away by them, and it was not for some years that he estimated them at their true value. Meanwhile the new geology made its appearance with the publication of the three volumes of his own _Principles of Geology_, between 1829 and 1833. The significance of the book for biological speculation--for theories of the origin of species--lay in its thesis that the present condition of the earth is the product of geological processes incalculably long. Hitherto the "catastrophic theory" had been dominant--the notion that a series of immense catastrophic events (like the Deluge) had been responsible for the present condition of the earth's surface. For this Lyell substituted his "Evolutionary Theory," according to which the almost invisibly slow geological processes which we may now see operating around us, are typical of the behaviour of the crust of this planet for incalculable periods of time; for even the slowest changes, if sufficient time is allowed them, are capable of producing the most stupendous results. Lyell may be said to have extended the age of the earth _ad infinitum_. Just as Galileo removed all barriers of space, Lyell removed those of time. Their joint achievement was to present to humanity a universe infinite both in space and time--a staggering conception.

RESULTS OF LYELL'S THEORY.--Though Lyell's boldness disturbed a good many of his contemporaries, those biologists who were engaged upon seeking the origin of species were thankful to one who had removed the chief obstacle to the solution of their difficulties. They were now relieved of one embarrassment: Lyell gave them the power to draw on the Bank of Time to any extent; bankruptcy was no longer possible.[37]

Indeed, Lyell seems himself to have been convinced of the evolutionary origin of species (though the mode of its operation still remained a mystery for him no less than for the biologists themselves). In fact, it became quite evident that the idea of "continuity" which the _Principles of Geology_ had established in the inorganic world, must be equally applicable to the organic world.

DARWIN.--The theory of a common descent of species had occurred, as early as 1837, to an enthusiastic student of Lyell's writings, who was also a personal friend. Charles Darwin had collected much geological, botanical, and zoological matter on his voyage with the _Beagle_ round the world, and continued for twenty years to accumulate an immense volume of _data_ to substantiate a theory which had first suddenly suggested itself to him in 1838 as the result of reading for amusement Malthus' _Essay on the Principle of Population_.

This celebrated book, first published in 1798, had attempted to describe the forces which ensure the multiplication, or check the increase of population. The proposition laid down by Malthus was that population tends to vary with the means of subsistence. He had studied his problem from a social or political point of view, but the same principle was seen by Darwin to apply to all living creatures. Two forces are seen everywhere in conflict: (a) the luxuriant powers of reproduction possessed by and exercised by each species; (b) the difficulties and obstacles by which the species tend to be eliminated. The contest between the powers of reproduction and those of elimination--this "over-production" and "crowding-out"--is what was afterwards termed the "struggle for existence."

"NATURAL SELECTION."--Darwin's momentous theory was that this struggle, proceeding for untold ages, had resulted in the continual formation of new species. Granted that the numerous offspring of any individual member of a species tend to vary, those variations survive which happen to be best fitted to cope with the environment. These in their turn leave offspring, the variations and the selections are repeated, and so on _ad infinitum_; and the result is that entirely new species are formed by a long process of insignificant changes. This, briefly put, is the celebrated theory of "Natural Selection."

The habit of scientific caution was characteristic of Darwin, who at first would not write down "even the briefest sketch" of his hypothesis, but devoted nearly twenty years to the accumulation of evidential _data_. His friends continually warned him that he would be forestalled, and this actually occurred, as is well known, in 1858, when the book which was to give the new theory to the world was already half written. The naturalist, Alfred Russell Wallace, on a collecting expedition in the East Indies, "in a flash of insight" while sick with fever, found the same solution of the mystery that had puzzled biologists so long. Wallace's letter to Darwin, containing the abstract of his theory, came "like a bolt from the blue."

The behaviour of the two men was worthy of the highest traditions of scientific research. The matter was put into the hands of Lyell, and Wallace's paper, together with certain extracts from Darwin's unpublished notes, were read before the Linnean Society, and the preparation of Darwin's book was hurried on. In November, 1859, _The Origin of Species_ was published.

RESULTS OF DARWIN'S THEORY.--The importance (for the general trend of thought) of this joint achievement of Darwin and Wallace was considerable, and could not but be regarded as an extension of the mechanical theory. The origin of species might still to some extent remain mysterious (for "natural selection" was soon realised to be only one of many factors at work in evolution), yet the area of mystery was patently reduced, and the "inexplicable" driven further back. A formula had been provided, which seemed to be as valid, and likely to prove as permanent and fruitful in biological research as Newton's law of gravity had been in the realm of physics.

In point of fact, Darwin had only substituted new problems of "variation" and "heredity" for the old one of the diversity of species; but an impression was created by the new discoveries that a purely mechanical explanation of the origin of life and even of mind was within reach.

THE DESCENT OF MAN.--With regard to "mind," the impression was re-inforced by Darwin's next book--the _Descent of Man_, where the gap between man and the animals was finally bridged. The work was merely an extension of the principles previously applied by him, and as a theory it had been present to Darwin's mind as far back as 1837. As soon as he had become "convinced that species were mutable productions," he could not "avoid the belief that man must come under the same law."[38] Indeed the Descent was nothing more than a corollary to the _Origin of Species_. The earlier work contains the whole of Darwinism.

THE POSITION REACHED.--And with the full publication of Darwin's theories a point was reached when a more or less consistently materialistic position seemed possible. The foundations of such a position had been strengthened by the scientific atomism of Dalton, and the results of German research in the field of _organic_ chemistry seemed to open up possibilities of expressing even life in terms of matter. And, finally, the evolutionary hypothesis had reduced some of the most obscure biological problems to manageable proportions. The prospects for a purely naturalistic philosophy were phenomenally bright.

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