Lamarck, the Founder of Evolution Part 20

THE VIEWS OF ERASMUS DARWIN

Erasmus Darwin, the grandfather of Charles Darwin, was born in 1731, or twenty-four years after Buffon. He was an English country physician with a large practice, and not only interested in philosophy, mechanics, and natural science, but given to didactic rhyming, as evinced by _The Botanical Garden_ and _The Loves of the Plants_, the latter of which was translated into French in 1800, and into Italian in 1805. His "shrewd and homely mind," his powers of keen observation and strong common sense were revealed in his celebrated work _Zoonomia_, which was published in two volumes in 1794, and translated into German in 1795-99. He was not a zoologist, published no separate scientific articles, and his striking and original views on evolution, which were so far in advance of his time, appear mostly in the section on "Generation," comprising 173 pages of his _Zoonomia_,[152] which was mainly a medical work. The book was widely read, excited much discussion, and his views decided opposition.

Samuel Butler in his _Evolution, Old and New_ (1879) remarks: "Paley's _Natural Theology_ is written throughout at the _Zoonomia_, though he is careful, _moro suo_, never to mention this work by name. Paley's success was probably one of the chief causes of the neglect into which the Buffonian and Darwinian systems fell in this country." Dr. Darwin died in the same year (1802) as that in which the _Natural Theology_ was published.

Krause also writes of the reception given by his contemporaries to his "physio-philosophical ideas." "They spoke of his wild and eccentric fancies, and the expression 'Darwinising' (as employed, for example, by the poet Coleridge when writing on Stillingfleet) was accepted in England nearly as the ant.i.thesis of sober biological investigation."[153]

The grandson of Erasmus Darwin had little appreciation of the views of him of whom, through atavic heredity, he was the intellectual and scientific child. "It is curious," he says in the 'Historical Sketch' of the _Origin of Species_--"it is curious how largely my grandfather, Dr. Erasmus Darwin, antic.i.p.ated the views and erroneous grounds of opinion of Lamarck in his _Zoonomia_ (vol. i., pp. 500-510), published in 1794." It seems a little strange that Charles Darwin did not devote a few lines to stating just what his ancestor's views were, for certain of them, as we shall see, are antic.i.p.ations of his own.

The views of Erasmus Darwin may thus be summarily stated:

1. All animals have originated "from a single living filament" (p. 230), or, stated in other words, referring to the warm-blooded animals alone, "one is led to conclude that they have alike been produced from a similar living filament" (p. 236); and again he expresses the conjecture that one and the same kind of living filament is and has been the cause of all organic life (p. 244). It does not follow that he was a "spermist," since he strongly argued against the incas.e.m.e.nt or "evolution" theory of Bonnet.

2. Changes produced by differences of climate and even seasons. Thus "the sheep of warm climates are covered with hair instead of wool, and the hares and partridges of the lat.i.tudes which are long buried in snow become white during the winter months" (p. 234). Only a pa.s.sing reference is made to this factor, and the effects of domestication are but cursorily referred to. In this respect Darwin's views differed much from Buffon's, with whom they were the primary causes in the modification of animals.

The other factors or agencies are not referred to by Buffon, showing that Darwin was not indebted to Buffon, but thought out the matter in his own independent way.

3. "Fifthly, from their first rudiment or primordium to the termination of their lives, all animals undergo perpetual transformations, which are in part produced by their own exertions in consequence of their desires and aversions, of their pleasures and their pains, or of irritations or of a.s.sociations; and many of these acquired forms or propensities are transmitted to their posterity" (p. 237). The three great objects of desire are, he says, "l.u.s.t, hunger, and security" (p. 237).

4. Contests of the males for the possession of the females, or law of battle. Under the head of desire he dwells on the desire of the male for the exclusive possession of the female; and "these have acquired weapons to combat each other for this purpose," as the very thick, s.h.i.+eld-like h.o.r.n.y skin on the shoulders of the boar, and his tusks, the horns of the stag, the spurs of c.o.c.ks and quails. "The final cause," he says, "of this contest among the males seems to be that the strongest and most active animal should propagate the species, which should thence become improved" (p. 238). This savors so strongly of s.e.xual selection that we wonder very much that Charles Darwin repudiated it as "erroneous." It is not mentioned by Lamarck, nor is Dr. Darwin's statement of the exertions and desires of animals at all similar to Lamarck's, who could not have borrowed his ideas on appetency from Darwin or any other predecessor.

5. The transmission of characters acquired during the lifetime of the parent. This is suggested in the following crude way:

"Thirdly, when we enumerate the great changes produced in the species of animals before their maturity, as, for example, when the offspring reproduces the effects produced upon the parent by accident or cultivation; or the changes produced by the mixture of species, as in mules; or the changes produced probably by the exuberance of nourishment supplied to the fetus, as in monstrous births with additional limbs, many of these enormities of shape are propagated and continued as a variety, at least, if not as a new species of animal. I have seen a breed of cats with an additional claw on every foot; of poultry also with an additional claw, and with wings to their feet, and of others without rumps. Mr. Buffon mentions a breed of dogs without tails, which are common at Rome and Naples, which he supposes to have been produced by a custom, long established, of cutting their tails close off. There are many kinds of pigeons admired for their peculiarities which are more or less thus produced and propagated."[154]

6. The means of procuring food has, he says, "diversified the forms of all species of animals. Thus the nose of the swine has become hard for the purpose of turning up the soil in search of insects and of roots.

The trunk of the elephant is an elongation of the nose for the purpose of pulling down the branches of trees for his food, and for taking up water without bending his knees. Beasts of prey have acquired strong jaws or talons. Cattle have acquired a rough tongue and a rough palate to pull off the blades of gra.s.s, as cows and sheep. Some birds have acquired harder beaks to crack nuts, as the parrot. Others have acquired beaks to break the harder seeds, as sparrows. Others for the softer kinds of flowers, or the buds of trees, as the finches. Other birds have acquired long beaks to penetrate the moister soils in search of insects or roots, as woodc.o.c.ks, and others broad ones to filtrate the water of lakes and to retain aquatic insects. All which seem to have been gradually produced during many generations by the perpetual endeavors of the creature to supply the want of food, and to have been delivered to their posterity with constant improvement of them for the purpose required" (p. 238).

7. The third great want among animals is that of security, which seems to have diversified the forms of their bodies and the color of them; these consist in the means of escaping other animals more powerful than themselves.[155] Hence some animals have acquired wings instead of legs, as the smaller birds, for purposes of escape. Others, great length of fin or of membrane, as the flying-fish and the bat. Others have acquired hard or armed sh.e.l.ls, as the tortoise and the Echinus marinus (p. 239).

"The colors of insects," he says, "and many smaller animals contribute to conceal them from the dangers which prey upon them.

Caterpillars which feed on leaves are generally green; earthworms the color of the earth which they inhabit; b.u.t.terflies, which frequent flowers, are colored like them; small birds which frequent hedges have greenish backs like the leaves, and light-colored bellies like the sky, and are hence less visible to the hawk, who pa.s.ses under them or over them. Those birds which are much amongst flowers, as the goldfinch (_Fringilla carduelis_), are furnished with vivid colors. The lark, partridge, hare, are the color of dry vegetables or earth on which they rest. And frogs vary their color with the mud of the streams which they frequent; and those which live on trees are green. Fish, which are generally suspended in water, and swallows, which are generally suspended in air, have their backs the color of the distant ground, and their bellies of the sky. In the colder climates many of these become white during the existence of the snows. Hence there is apparent design in the colors of animals, whilst those of vegetables seem consequent to the other properties of the materials which possess them" (_The Loves of the Plants_, p. 38, note).

In his _Zoonomia_ (-- x.x.xix., vi.) Darwin also speaks of the efficient cause of the various colors of the eggs of birds and of the hair and feathers of animals which are adapted to the purpose of concealment.

"Thus the snake, and wild cat, and leopard are so colored as to resemble dark leaves and their light interstices" (p. 248). The eggs of hedge-birds are greenish, with dark spots; those of crows and magpies, which are seen from beneath through wicker nests, are white, with dark spots; and those of larks and partridges are russet or brown, like their nests or situations. He adds: "The final cause of their colors is easily understood, as they serve some purpose of the animal, but the efficient cause would seem almost beyond conjecture." Of all this subject of protective mimicry thus sketched out by the older Darwin, we find no hint or trace in any of Lamarck's writings.

8. Great length of time. He speaks of the "great length of time since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind" (p. 240).

In this connection it may be observed that Dr. Darwin emphatically opposes the preformation views of Haller and Bonnet in these words:

"Many ingenious philosophers have found so great difficulty in conceiving the manner of the reproduction of animals that they have supposed all the numerous progeny to have existed in miniature in the animal originally created, and that these infinitely minute forms are only evolved or distended as the embryon increases in the womb. This idea, besides being unsupported by any a.n.a.logy we are acquainted with, ascribes a greater tenuity to organized matter than we can readily admit" (p. 317); and in another place he claims that "we cannot but be convinced that the fetus or embryon is formed by apposition of new parts, and not by the distention of a primordial nest of germs included one within another like the cups of a conjurer" (p. 235).

9. To explain instinct he suggests that the young simply imitate the acts or example of their parents. He says that wild birds choose spring as their building time "from the acquired knowledge that the mild temperature of the air is more convenient for hatching their eggs;" and further on, referring to the fact that seed-eating animals generally produce their young in spring, he suggests that it is "part of the traditional knowledge which they learn from the example of their parents."[156]

10. Hybridity. He refers in a cursory way to the changes produced by the mixture of species, as in mules.

Of these ten factors or principles, and other views of Dr. Darwin, some are similar to those of Lamarck, while others are directly opposed.

There are therefore no good grounds for supposing that Lamarck was indebted to Darwin for his views. Thus Erasmus Darwin supposes that the formation of organs precedes their use. As he says, "The lungs must be previously formed before their exertions to obtain fresh air can exist; the throat or oesophagus must be formed previous to the sensation or appet.i.tes of hunger and thirst" (_Zoonomia_, p. 222). Again (_Zoonomia_, i., p. 498), "From hence I conclude that with the acquisition of new parts, new sensations and new desires, as well as new powers, are produced" (p. 226). Lamarck does not carry his doctrine of use-inheritance so far as Erasmus Darwin, who claimed, what some still maintain at the present day, that the offspring reproduces "the effects produced upon the parent by accident or cultivation."

The idea that all animals have descended from a similar living filament is expressed in a more modern and scientific way by Lamarck, who derived them from monads.

The Erasmus Darwin way of stating that the transformations of animals are in part produced by their own exertions in consequence of their desires and aversions, etc., is stated in a quite different way by Lamarck.

Finally the principle of law of battle, or the combat between the males for the possession of the females, with the result "that the strongest and most active animal should propagate the species," is not hinted at by Lamarck. This view, on the contrary, is one of the fundamental principles of the doctrine of natural selection, and was made use of by Charles Darwin and others. So also Erasmus antic.i.p.ated Charles Darwin in the third great want of "security," in seeking which the forms and colors of animals have been modified. This is an antic.i.p.ation of the principle of protective mimicry, so much discussed in these days by Darwin, Wallace, and others, and which was not even mentioned by Lamarck. From the internal evidence of Lamarck's writings we therefore infer that he was in no way indebted to Erasmus Darwin for any hints or ideas.[157]

FOOTNOTES:

[152] Vol. ii., 3d edition. Our references are to this edition.

[153] Krause, _The Scientific Works of Erasmus Darwin_, footnote on p. 134: "See 'Athenaeum,' March, 1875, p. 423."

[154] _Zoonomia_, i., p. 505 (3d edition, p. 335).

[155] The subject of protective mimicry is more explicitly stated by Dr. Darwin in his earlier book, _The Loves of the Plants_, and, as Krause states, though Rosel von Rosenhof in his _Insekten-Bel.u.s.tigungen_ (Nurnberg, 1746) describes the resemblance which geometric caterpillars, and also certain moths when in repose, present to dry twigs, and thus conceal themselves, "this group of phenomena seems to have been first regarded from a more general point of view by Dr. Darwin."

[156] _Zoonomia_, vol. i., p. 170.

[157] Mr. Samuel Butler, in his _Evolution, Old and New_, taking it for granted that Lamarck was "a partisan of immutability till 1801,"

intimates that "the secret of this sudden conversion must be found in a French translation by M. Deleuze of Dr. Darwin's poem, _The Loves of the Plants_, which appeared in 1800. Lamarck--the most eminent botanist of his time--was sure to have heard of and seen this, and would probably know the translator, who would be able to give him a fair idea of the _Zoonomia_" (p. 258).

But this notion seems disproved by the fact that Lamarck delivered his famous lecture, published in 1801, during the last of April or in the first half of May, 1800. The views then presented must have been formed in his mind at least for some time--perhaps a year or more--previous, and were the result of no sudden inspiration, least of all from any information given him by Deleuze, whom he probably never met. If Lamarck had actually seen and read the _Zoonomia_ he would have been manly enough to have given him credit for any novel ideas. Besides that, as we have already seen, the internal evidence shows that Lamarck's views were in some important points entirely different from those of Erasmus Darwin, and were conceptions original with the French zoologist.

Krause in his excellent essay on the scientific works of Erasmus Darwin (1879) refers to Lamarck as "evidently a disciple of Darwin," stating that Lamarck worked out "in all directions" Erasmus Darwin's principles of "will and active efforts" (p. 212).

CHAPTER XV

WHEN DID LAMARCK CHANGE HIS VIEWS REGARDING THE MUTABILITY OF SPECIES?

Lamarck's mind was essentially philosophical. He was given to inquiring into the causes and origin of things. When thirty-two years old he wrote his "Researches on the Causes of the Princ.i.p.al Physical Facts," though this work did not appear from the press until 1794, when he was fifty years of age. In this treatise he inquires into the origin of compounds and of minerals; also he conceived that all the rocks as well as all chemical compounds and minerals originated from organic life. These inquiries were reiterated in his "Memoirs on Physics and Natural History," which appeared in 1797, when he was fifty-three years old.

The atmosphere of philosophic France, as well as of England and Germany in the eighteenth century, was charged with inquiries into the origin of things material, though more especially of things immaterial. It was a period of energetic thinking. Whether Lamarck had read the works of these philosophers or not we have no means of knowing. Buffon, we know, was influenced by Leibnitz.

Did Buffon's guarded suggestions have no influence on the young Lamarck?

He enjoyed his friends.h.i.+p and patronage in early life, frequenting his house, and was for a time the travelling companion of Buffon's son. It should seem most natural that he would have been personally influenced by his great predecessor, but we see no indubitable trace of such influence in his writings. Lamarckism is not Buffonism. It comprises in the main quite a different, more varied and comprehensive set of factors.[158]

Was Lamarck influenced by the biological writings of Haller, Bonnet, or by the philosophic views of Condillac, whose _Essai sur l'Origine des Connaissances humaines_ appeared in 1786; or of Condorcet, whom he must personally have known, and whose _Esquisse d'un Tableau historique des Progres de l'Esprit humain_ was published in 1794?[159] In one case only in Lamarck's works do we find reference to these thinkers.

Was Lamarck, as the result of his botanical studies from 1768 to 1793, and being puzzled, as systematic botanists are, by the variations of the more plastic species of plants, led to deny the fixity of species?

We have been unable to find any indications of a change of views in his botanical writings, though his papers are prefaced by philosophical reflections.

It would indeed be interesting to know what led Lamarck to change his views. Without any explanation as to the reason from his own pen, we are led to suppose that his studies on the invertebrates, his perception of the gradations in the animal scale from monad to man, together with his inherent propensity to inquire into the origin of things, also his studies on fossils, as well as the broadening nature of his zoological investigations and his meditations during the closing years of the eighteenth century, must gradually have led to a change of views.

It was said by Isidore Geoffroy St. Hilaire that Lamarck was "long a partisan of the immutability of species,"[160] but the use of the word "partisan" appears to be quite incorrect, as he only in one instance expresses such views.