Lamarck Revisited ERNST MAYR Museum of Comparative Zoology Harvard University As long as the battle between Darwinism and Lamarckism was raging, it was quite impossible to undertake an unbiased evalua- tion of Lamarck. For this we are now ready, after it has been demonstrated conclusively that the various causal explanations of evolution, usually designated as Lamarckism, are not valid. Not that it really needed this final proof, but the recognition that DNA does not directly participate in the making of the phenotype and that the phenotype, in turn, does not control the composition of the DNA, represents the ultimate invalidation of all theories involving the inheritance of acquired characters. This definitive refutation of Lamar&s theory of evolutionary causation clears the air. We can now study him without bias and emotion and give him the attention which this major figure in the history of biology clearly deserves. The past study of Lamarck (1744-1829) has tended to suffer from one-sided approaches. Sometimes he was discussed under the heading, “Lamarck and Darwin”: Did he anticipate Darwin? Did Darwin build on a foundation laid by Lamarck? Did Darwin fail to give him sufficient credit? It would be futile to try to reach a well-balanced evaluation of Lamarck through answering such one-sided questions. Other authors have limited their study to a comparison of Lamar&s ideas with those of such eighteenth- century philosophers as had an interest in evolution, like Diderot, Maupertuis, or Robinet. This approach utterly fails to consider the contributions made by Lamar&s professional interests. After all, he was not primarily a philosopher, but made his living as a naturalist who studied plants and animals for more than fifty years, from 1770 (when he was twenty-six) to the 1820’s (when he was in his eighties). Some recent historians (Gillispie, 1956, 1959; Willkie, 1959; Simpson, 1961, 1964) have perhaps stressed too strongly the negative aspects of Lamar&s work. They have stated, not with- Journal of the History of Biology, vol. 5, no. 1 (Spring 1972), pp. 55-94. 55 ERNSTMAYR out justification, that his theory of evolution was neither new nor valid; that he did not propose a feasible mechanism of evolution; that, as an evolutionist, he was hardly ever mentioned by his contemporaries; that he seemed to have had singularly little influence on the subsequent development of evolutionary think- ing; and that, when later in the nineteenth century his name was applied to evolutionary mechanisms, it was usually to ones not at all stressed by Lamarck himself. All this is largely true, and yet it does not do justice to Lamarck as a figure in the history of biology. There are two excellent evaluations of Lamar&s work in French. That of Daudin (1926) is largely limited to Lamar&s taxonomy, a subject which I will not discuss here, since I plan to treat it elsewhere. That of Guyenot (1941:415-439) is a sympathetic and reliable introduc- tion into Lamar&s thought (and its connections with his pre- decessors), but it does not pretend to be a full analysis. There is also Landrieu’s (1909) extensive biography of Lamarck. A truly penetrating study of Lamarck is still a desideratum. Eventually we will want to know far more about the growth of his thought, both before and after 1800. We will want to know to what extent his system of thought consisted of widely (at his time!) accepted “truths,” such as the inheritance of acquired characters, and to what other part it was based on special philo- sophies and beliefs, such as deism, the concept of plenitude, and various aspects of the philosophies of Leibniz, Newton, or Descartes. This will require an extensive study of the thought of the eighteenth century. Only one of Lamarck’s biological publications, the Philosophic zoologique (1809), was ever translated into English, and even that one not until more than 100 years after its publication (Lamarck, 1914). For ease of reference I am basing my analysis almost entirely on the Philosophic zoologique, even though I fully realize that it is a confusing and repetitive work. One sometimes has the impression that Lamarck had merely gathered together his lecture notes over many years and combined them with portions of the Discours d’ouverture (Lamarck, 1907). How else can one explain that the identical topic is sometimes treated on six or ten different pages and his conclusions stated on these pages in virtually identical sentences? On the other hand, since no Lamarck “Notebooks” are in existence, this somewhat chaotic work may permit a better insight into the workings of Lamar&s mind than the more polished final revision that was published as the introduction to the Histoire naturetle des animaux sans VertBbres (1815). 56 Lamarck Revisited The emphasis in my own treatment is on three aspects of Lamar&s work. It attempts (1) to bring out as clearly as possible what Lamarck actually thought and said; (2) to show where Lamarck got himself entangled in contradictions, in part because his findings as a zoologist were in conflict with his philosophical concepts; and (3) to point out problems that are in need of further research. In other words, this essay is a prolegomenon to the study of Lamarck rather than a comprehen- sive work on this great naturalist. My comments are primarily those of a biologist, not those of a historian. I have made no attempt to analyze the non-evolutionary writings of Lamarck, as for instance Parts II and III of the Philosophic zoologique. Greene (1959) has indicated the importance of this sector of Lamar&s work. Nor have I attempted to follow in detail the changes in Lamar&s thought throughout his long life. One of my major objectives is to help English-speaking zoologists to become better acquainted with Lamar&s work. Extensive quotations from the Philosophie zoologique are pro- vided under each subject heading,1 and I hope that they will show the reader not only how manfully (and often futilely) Lamarck struggled with facts and concepts, but also that Lamarck was a better observer and more perceptive thinker than he is usually given credit for. PSEUDO-LAMARCKISM Paradoxically, and as a consequence of a long tradition of historical interpretation, one must begin a discussion of Lamarck by emphasizing what the naturalist did not say. Two explanatory principles, in particular, are consistently but quite wrongly claimed to be the cornerstones of Lamar&s thinking: (1) direct effect of the environment, and (2) evolution through volition. ( 1) Direct effect of the environment When one checks the literature of Neo-Lamarckism to find out which concept is most consistently designated as “Lamarclian,” one finds that it is the belief in a direct induction of hereditary changes in organisms by the environment. Curiously, as Simpson (1961) points out, Lamarck himself emphatically rejected the 1. Virtually all recent treatments of Lamarck merely provide an abstract of Lamar&s ideas. This is legitimate for most purposes. The particular flavor of Lamar&s reasoning, however, is lost by the mere summarizing of his ideas. I hope that the exact page references will help future students to find their way through the Philosophie zoologique, which is not an easy work to read. All page references (in parentheses) after quotations from the Philosophic zoologique refer to the Elliot translation. 57 ERNST MAYR existence of such an evolutionary cause. However, since he speaks again and again of “the influence of the environment,” he realizes the need for an explanation: “I must now explain what I mean by this statement: The environment affects the shape and organization of animals, that is to say that when the environment becomes very different, it produces in the course of time corresponding modifications in the shape and organization of animals. “It is true, if this statement were to be taken literally, I should be convicted of an error; for, whatever the environment may do, it does not work any direct modification whatever in the shape and organization of animals” (p. 107). He then explains how he himself envisions the effect of the environment. Lamarck believed that “alterations in the environ- ment of animals lead to great alterations in their needs, and these alterations in their needs necessarily lead to others in their activity” (p. 107). This interpretation is repeated many times throughout the Philosophie zoologique (pp. 40, 41, 43, 45, 58, and 114). In spite of this emphatic rejection of direct induction for higher animals which display “activity,” one finds that Lamar& speaks equally freely of a modifying influence of the environ- ment on plants and lower (e.g., sessile) invertebrates. Would this not indicate that, at least in immobile organisms, he did have some belief in direct induction? And to what extent did Btienne Geoffroy St, Hilaire owe his belief in direct induction to Lamarck? These are still unanswered questions. (2) The effect of volition The other explanatory principle erroneously ascribed to Lamarck is the effectiveness of volition. The popular cartoon on Lamarckism depicts an animal, preferably a giraffe, wishing to reach an objective and through this volition growing (or acquiring) the needed structure (let us say, a longer neck). The attribution of this belief to Larnarck goes far back, for even Darwin speaks of “Lamarck nonsense of . adaptations from the slow willing of animals” (letter of January 11, 1844, to J. D. Hooker). Actually, as pointed out by Cannon (1957), Lamarck never said anything of the sort. The error presumably arose from a mistranslation of “besoin” (need). Lye11 already scolded Darwin (in a letter of October 3, 1859) for ascribing to Lamarck a theory of volition.