Chapter 15 Chapter 8 Evolutionary thought before Darwin-1

From the point of view of modern biologists, from Leibniz's first provocative discussion of evolutionism in his book "Protosaea" (1694) to Mark's explicit proposal of this The time interval (lag) between arguments (1800) is far too long.Buffon remained indecisive on the question of evolution throughout his life, and many other thinkers adopted the view of the great chain of nature represented by time, but none of them took firm steps to bring this ever-perfecting, continuous chain of divine creation to the next level. Transform into a family tree passed down from generation to generation.

Lamarck (Jean Bantiste Pierre Antoine de Monet, Chevalier de Lamarck, 1744-1829) was born in a declining noble family in northern France.He joined the army at the age of 17 and fought bravely in the 7-year war; he retired at the age of 19 due to injuries and the end of the war. Since then, he has been living in Paris on a meager allowance and selling labor.Later he was particularly interested in natural history, especially botany, and finally wrote a four-volume collection of French flora, which was very popular for its exquisite description.Soon after he was hired by Buffon as his son's tutor and traveling companion.This gave Lamarck the opportunity to travel to Italy and other European countries, which was the only trip in his life. In 1788 Buffon secured him an assistantship in the botanical department of the Museum of Natural History, where he remained for five years.Lamarck has a wide range of interests and hobbies. He has been interested in plants for nearly 30 years and has published a large number of works.At that time he undoubtedly believed in a "first created" and subsequently unchanging species with distinct boundaries.Some of his statements clearly show that his thinking during that period was that of an essentialist.

In 1793, with the reorganization of the French scientific research institutions, Lamarck was appointed professor of "lower animals"; the so-called lower animals at that time were the invertebrates now, and the invertebrates were named by Lamarck.This new appointment was decisive in his life.He used great enthusiasm and energy to get acquainted with all kinds of animals that Linnaeus generally classified as "worms".Lamarck was forty-nine when he began these new studies, which apparently had an extremely profound impact on his thinking.Until then he had adhered to typical eighteenth-century thinking, a mixture of deism and a synthesis of Newtonian and Leibnizian thought.From Newton he accepted the rationality of the universe and believed that all phenomena (whether inorganic or biological) could be explained in terms of motion and forces applied to matter.From Leibniz he accepted the optimistic estimate that the universe is perfect harmony and perfect principle and continuity.However, this synthesis (that is, the synthesis of Newton's and Leibniz's ideas) gave rise to many contradictions, and his theory of evolution was obviously an attempt to resolve these contradictions, or at least the result of resolving some of them.

Lamarck once had a grand project of compiling a "global physics" (including biology), for which he dabbled in almost all disciplines.He was ridiculed for his meteorological predictions and against Lavoisier's great new discovery (discovery of oxygen).He also wrote a book on geology, but his contemporaries paid little attention to it, and there was no English translation until more than ten years ago. His new appointment as a professor requires him to teach a year-long course on invertebrates.For several years Lamarck gave the first lecture of the course as a "Dkcours douverture" (Dkcours douverture).The manuscripts (at least some of them) of these lectures (prologues) have survived and some have been published in recent years. The opening remarks of 1799 still represent Lamarck's thinking: the species remains unchanged, and there is not the slightest hint of evolution.This idea of ​​Lamarck is inherited from the botanist de Jussieu and the Linnaean school.The "prologue" of the second year was a lecture given by Lamarckian on May 11, 1800, in which he presented Lamarck's new theory of evolution, which already contained his book "Philosophy of Animals" (1809). ) of the basics.Apparently Lamarck had a conversion "return" (in religious terms) between 1799 and 1800.What could have caused a fifty-five-year-old man to abandon his original views and replace them with such radical views that no one had ever held before?

Past efforts to explain Lamarck's theory of evolution have almost invariably been unsatisfactory because they have failed to separate Lamarck's ideas of change in relation to evolution from the physiological and genetic mechanisms he used to explain those changes.In the following discussion I try to carefully distinguish these two aspects of Lamarckian theory of evolution. In the discussion that follows I will also try to present Lamarck in the intellectual context of the time.Few in the past have been so severely misrepresented by Whigg historians (see Chapter 1) as Lamarck.Indeed, he is one of the most difficult figures in the history of biology.This is perhaps why there are more different interpretations, and even different statements, of Lamarck's ideas than anyone else's.Needless to say, just take the introductions of Meyer, Hodge and Burxhardt in recent years to understand this.Lamarck was deeply influenced or taught by Descartes, Newton, Leibniz, and Buffon in terms of reason and knowledge. However, his thoughts were also obviously influenced by his zoological research, especially the variation and fossils of molluscs. Impact on historical research. Hodge (1917) rightly pointed out that Lamarck cannot and should not be interpreted in terms of Darwin's theory of evolution.Lamarck did not propose a theory of the origin of species, nor did he consider the question of common ancestry.What is most remarkable about an early nineteenth-century naturalist is that he did not consider geographical distribution at all, which is one of the strongest arguments for Darwin's theory of common ancestry.

Lamarck's New Model Lamarck claimed that his new theory was necessary to account for two well-known phenomena in the biological world.The first phenomenon is that animals display different degrees of "perfection."In the case of gradual increase in completeness, Lamarck realized that from the simplest animal to the most complex animal, and finally to human beings, the "animality" (animality) is gradually enhanced.He does not evaluate completeness in terms of adaptation to the environment or the role an animal plays in nature, but only in terms of complexity.Another phenomenon that needs to be explained is the amazing diversity of life, which shows that "everything that can be imagined actually happens and exists." It seems that Lamarck is referring here to the principle of perfection.

Another point that Lamarck added was the actual transition of species in the phylogenetic tree. "After many successive generations. . . . Individuals who originally belonged to a certain species finally transformed into a new species different from the original species." Lamarck repeatedly talked about the slowness and gradualness of evolution on many occasions. "As far as the living world is concerned, there is no doubt that everything that nature does is carried out step by step and continuously." When discussing the original aquatic animals, he said: "Nature guides them to gradually become accustomed to living in the air. , first by the water, and so on."

"These changes are so slow that they are always imperceptible." "The character and external character of any living being must change imperceptibly, although it is difficult to deny this; it takes a considerable time to perceive it." change." "There is no doubt that a very long and profound series of changes in time and conditions were required to enable nature to develop the structure of animals to a certain degree of complexity, and from this complexity to know the degree of completeness of animals. ".This can be done, because "time is endless and can be drawn indefinitely" as far as nature is concerned (the above quotations are all quoted from Lamarck's "Animal Philosophy", 1809).

Many historians who study Lamarck tend to ask themselves what new discoveries or new insights prompted Lamarck to adopt this new view in 1800.According to Burkhardt (1977), Lamarck took over the mollusc collection of the Musée de Paris after the death of his friend Brugiere in the late 1790s.When he began to study the collection, which included both fossils and recent mollusks, he found that many mussels (oysters) and other marine molluscs were similar to living and fossil species.In many cases it is indeed possible to arrange the early fossils and the fossils of the more recent Tertiary strata in historical order from modern species onwards.In the case of fairly complete data, it can even be arranged in an almost uninterrupted pedigree.In some cases, Lamarck found modern species stretching far back into Tertiary strata.The inevitable conclusion, then, is that many germline series have undergone a slow and gradual change in time.There is probably no other animal more suitable for drawing such a conclusion than the marine molluscs.

Cuvier also studied fossil mammals around this time, and mammals in general evolved much faster than marine molluscs.In his studies Cuvier found no analogous extant species of the fossil elephant or some other fossil animal, leading to the conclusion that the earlier species had become extinct and had been replaced by entirely new ones.Noting phylogenetic series was especially important for Lamarck, because it solved a problem that had plagued him for a long time: the problem of (species) extinction. With the increasingly extensive and in-depth study of fossils, many fossil species have been found to be quite different from existing species.An obvious example is the ammonites, which are abundant in Mesozoic sediments. The situation became more sensitive after the discovery of fossil mammals (mastodons in North America, mammoths in Siberia) in the 18th century.Later, Cuvier described all the fossil mammals excavated from different layers of strata in the Paris Basin.More serious naturalists and fossilologists end up agreeing that some of the animals that inhabited the earth early became extinct, but not all at the same time.For example, Blumenbach believes that there are two extinction periods, the earlier extinction period is mainly related to the extinction of marine organisms such as bivalve molluscs, ammonites and perforated molluscs, and the recent extinction period involves some extant relative species Creatures such as cave bears and mammoths. Herder had earlier spoken of the Earth's multiple cycles, other scholars had referred to catastrophes, and the end result of all these causes was extinction.As far as other naturalists are concerned, the concept of extinction of species cannot be accepted for certain ideological reasons, as far as the natural theists are concerned, as well as the Newtonian school and their followers, everything in the universe is governed by laws, so They thought extinction was unthinkable.Extinction also violates the principle of perfection, since the extinction of a species will leave a void in the perfection of nature.Finally, it also violates the concept of natural balance, which would not provide any justification for extinction (Lovejoy, 1936, especially pp. 243, 256).

The idea that species extinction was incompatible with God's omnipotence and mercy was prevalent throughout the eighteenth century. Ray (Ray) once said at a fossil seminar in 1703: "From this we can see that many crustaceans have disappeared from the world. This fact is not accepted by some previous philosophers. They think that The annihilation of any one species is the dissolution of the universe and makes it no longer whole; and they also hold that providence is especially concerned with the safety and protection of things created by God" (Physio-Theological Dialogues, third edition, 1713). Most philosophers during the Enlightenment and the first half of the nineteenth century were deists, and their God was one who, once created, would not let him interfere in the affairs of the universe.Any such intervention would be a miracle, and who among the philosophers would support miracles since Hume and Voltaire ridiculed them?This creates a dilemma.Either to deny that extinctions occurred, which is the attitude Lamarck (more or less) adopted; or to assume that at the beginning of creation a law had been established that species would disappear regularly throughout geological time, with New species are produced regularly.However, if it is not "special creation" ("special creation"), this "introduction of new species" How can the law of the law work?This was an argument advanced (but never fully expressed) by Darwin against Lyell, who had asserted such a law.Now let's turn back to how people try to "explain away" the idea of ​​extinction. Four explanations were proposed in the 17th and 18th centuries to explain the disappearance of fossil species, none of which had anything to do with "natural extinction". The first explanation is that the extinct animals were wiped out by Noah's flood or some other catastrophe.This explanation was widely popular in the first half of the 19th century, but it contradicted Lamarck's gradualism; and since many of the "disappeared species" were aquatic organisms, it seems unreasonable to say that they died due to floods. The second explanation is that supposedly extinct species are likely still living in unexplored parts of the earth. "There are still many parts of the earth's surface that we have not yet entered; , but only at random; there are also places, such as various parts of the ocean floor, where we have not yet had any means of discovering animals living there. Species unknown to us may well be hiding in these places" ("Animals philosophy"). Finally, there are those who explain the extinction of species as the result of human activities.This explanation was used in particular to account for the extinction of large mammals such as mammoths and mastodons. The above three explanations have not completely solved the problem of species extinction, and left many problems (if not most of them) to be solved.Thus, the discovery of fossil animals similar to living animals provided Lamarck with the long-sought answer. "Is it possible that ... the fossil in question belongs to an extant species, but has since changed into the same species we actually see today?" In other words, extinction is nothing more than a false question (Pseudo-Problem).The principle of perfection has not been violated in the slightest, and strange species found only in fossils still survive, but have been altered to such an extent that they are no longer recognizable, unless we have successive levels of fossils and (as we now often say) very Slow evolution rate.In this way, evolutionary (sexual) change is the answer to the problem of species extinction.On the other hand, studying evolution is another way to demonstrate the harmony of nature and the wisdom of the Creator. In reaching the above conclusions, Lamarck immediately perceives that there is another reason why this interpretation is perfectly logical.The Earth has been in perpetual change throughout the eons of its existence.As a species must be in perfect harmony with its environment, which is constantly changing, so in order for a species to be in harmony and balance with its environment, it (the species) itself must also be constantly changing.If it doesn't, it's in danger of extinction.By introducing the time factor, Lamarck discovered the Achilles' heel or the crux of natural theology.It is possible for the Creator to design a perfect biological organism for a brief period of time in a static world.But if the environment is constantly changing (and sometimes dramatically), how can a species remain fully adapted to its environment?If the earth has a lifespan of billions of years, how can design anticipate all climate change, changes in the physical structure of the earth's surface, and changes in the shifting components (predators and competitors) of the ecosystem?Under these circumstances, organisms can only keep adapting to the environment if they constantly adjust themselves according to these new situations, that is, if they evolve.Although natural theologians (who are also good naturalists) have clearly recognized the importance of the environment and the adaptation of organisms to the environment, they do not consider the time factor.Lamarck first clearly recognized the decisive role of this factor. Lamarck's new evolutionary ideas were strongly supported by her previous geological research.Like all Leibnizians, Lamarck was a uniformitarian (as were most 18th-century naturalists), he believed that the earth was extremely long-lived, and, like Buffon, , he didn't expect that the changes would continue to take place over such a long period of time.Things are forever changing, but very slowly.Such a picture of a gradually changing world fits well with the idea of ​​evolution.But it stands in stark contrast to Hutton's steady-state world, which does not include any directional changes and is therefore reluctant to accept an evolutionary perspective. Of course, the theory of evolution is even more incompatible with the idea of ​​essentialism, that is, with the belief in unchanging and discontinuous patterns. For essentialists, the fauna of the earth can only be changed by catastrophic events. Extinction and new creation to explain, this view is expressed in the writings of Cuvier and his disciples.Lamarck's staunch opposition to catastrophism of any kind is evident from his work on zoology, as well as from his Hydrogeology (1802). Although Lamarck's new theory of evolution has answered some questions, it still faces some insurmountable difficulties. If Lamarck was a blind follower of Bonnet's notion of the chain of being and of the gradual and continuous transition from the inanimate to the most perfect being which it emphasizes, then Lamarck All that was required was to apply his principles of species-transition (species change) to the ladder of nature; Lamarck, however, was not a step-by-step follower of Bonnet.Even in his early writings, Lamarck emphasized that there is no transition between the non-living and the living.Although Lamarck strongly supported the fundamental unity (identity) of animals and plants, he denied any transition between the two worlds. However, the conflict of opinion between Lamarck and Bonnet was deeper. Comparative anatomical studies carried out in Paris museums, especially those carried out in the 1790s, found that various morphological types (such as vertebrates, molluscs, Spiders, insects, worms, jellyfish, ciliates, etc.) find more and more discontinuities.Contrary to Bonnet's opinion, they do not form a graded series of species. "Such series do not exist, but rather I speak of almost random, ordered series (graduated series) of major classes such as families; such series do exist in both animals and plants; But when it comes to genera, and especially to species, such series tend to form side branches whose apexes are really isolated." The rectilinear chain cable image was gradually replaced in Lamarck's writings by a branched tree . In 1809 he identified two completely separate lineages of animals, one from ciliates to hydra and radiomorphs, and the other including most animal lineages beginning with naturally occurring worms.By 1815 Lamarck had identified even more genealogies. In Lamarck's view, the process of branching is the process of adaptation, not the process that can lead to species diversity, while Darwin and subsequent evolutionists believed that branching is closely related to species diversity.The diversity of organic life has become a vexing scientific problem for people who no longer believe that the world is designed and created.Spontaneous generation appears to be the only plausible stand-in for creationism to explain the origin of new genealogies (Farley, 1977).Lamarck said that in order for "living organisms to be indeed products of nature, nature must have been able, and must still be, to be able to produce certain organisms directly." Since Lamarck knew the work of Redi and Spallanzani, he and Moore Unlike Pedt, La Mettrie, and Diderot, he did not believe that organic molecules could combine in animals as complex as elephants, even at the warmer temperatures of Earth's past. "Nature seems to have performed only in the ciliates a direct or spontaneous generation, which is continually repeated, so long as the conditions are right; The abilities of all other animals known." Once these lower organisms had arisen, the known processes of evolution could further develop and perfect them. "Nature was and is beginning by first modifying the simplest organisms, which, as the term aeogenesis suggests, are the rudiments of organization." Lamarck also accepted without doubt that intestinal Tao worms are naturally occurring, and it is believed that this naturally occurring worm is the basis or starting point for the evolution of many higher animals.He also believed that the transition from a certain type of organism to a more complex organism was effected by the acquisition of a new ability as a result of the presence of a new structure or organ (see below). Was Lamarck the first staunch evolutionist? There are quite a few lists of "early evolutionists" in some histories of biology. H． F． Osborn, in his book From the Greeks to Darwin, is indeed full of introductions to those who preceded Darwin.But, as we saw in Chapter 7, careful analysis does not support this view.Pioneers should be those who propose either a theory of "origins" or a principle that demonstrates the inherent potential of the model.A true theory of evolution must assert a gradual transition from one species to another, and so on ad infinitum.This view is not to be found in the writings of de Maillet, Robinet, Diderot, and others who are said to have influenced Lamarck.Some of Lamarck's predecessors, such as Maupetui, once proposed the instantaneous origin of new species (instantaneous origin of new spedes).In his later writings, Linnaeus attached great importance to the possibility of unlimited generation of new species through hybridization.Buffon also once considered the possibility of a certain species being transformed into a related species, but flatly opposed extending it to a whole family that could be transformed into another family.For these pioneers, nature was largely static.Lamarck replaced this static world view with a dynamic world; in Lamarck's view, not only species, but the entire chain of nature and the overall balance of nature are in constant flux. Buffon has always emphasized the gulf between animals and humans.Lamarck, on the other hand, decisively bridged this gap by arguing that man is the end product of evolution.In fact, his description of the process of anthropoidization (transformation into humans) of human ancestors is very modern: "If a certain type of quadrumanous animals, especially the most complete type, Due to the force of the environment or other reasons, the habit of climbing trees and using their feet to support themselves has been lost. , then no doubt...these quadruped-handed individuals will eventually turn into bipeds whose thumbs will no longer be separated from the other toes when they walk on their feet,' and they will adopt an upright Posture for "wider and farther vision".Lamarck advances his view of the origin of man here ("The Philosophy of Animals") with greater courage than Darwin did fifty years later in .Humans "represent with great confidence the most perfect pattern that nature can achieve; therefore the closer an animal is to a structure that resembles that of a human, the more perfect it will be." Since evolution is a continuous process, so will humans. "This principal class, having acquired absolute predominance over all other animals, will at last establish a distinction between itself and the most perfect animals, and will indeed leave them far behind." Certain traits that neither animal has, or at least is not equally well developed, yet both humans and animals share most common physiological traits.These characteristics are often easier to study in animals than in humans, so in order to gain a full understanding of humans, "it is necessary to try to understand the structure of other animals." Aristotle once used the same reason to argue that his understanding of animals The study of natural history. Lamarck believed that there were two separate and independent causes of evolutionary change.The first reason is to seek more complex (perfect) talents. "In the successive production of various animals, nature begins with the most imperfect or simplest and ends with the most perfect, so that the structure of animals gradually becomes more complex." This trend towards more complex Tendency comes from "God-given power." "Can't the infinite power of God create an order in succession of all that we can see and that which exists but does not see?" Or as he put it in 1815 Putting it this way: Nature "given to animal life the power of increasing structural complexity." It is clear that acquiring the power of increasing structural complexity is, in Lamarck's view, an intrinsic potential of animal life.This is a law of nature and requires no special explanation. A second cause of evolutionary change is the ability to respond to particular conditions of the environment.Lamarck said that if the inner drive towards perfection were the only cause of evolution, there would be only a straight sequence leading to perfection. In nature, however, we find a variety of special adaptations in species and genera, not a straight sequence. Lamarck thought this was due to the fact that an animal must always be in total harmony with its environment, and when this coordination is broken, the animal re-establishes it through its behavior.The need to respond to particular circumstances of the environment gives rise to the following sequence of events: (1) considerable and continuous changes in the environment of animals of any kind cause real changes in their needs (besoins); (2) ) each change in the animal's needs requires an adjustment of their behavior (various actions) to meet the new need, resulting in the formation of different habits; (3) each new need requires new actions to be satisfied, so that The first requires animals to use certain parts of the body either more than before, thus developing and strengthening (enlarging) them; "("par des efforts de sentiments interieures") developed without knowing it. Lamarck was neither vitalist nor teleological.Even if it tends to "gradually complicate or refine the structure" Nor is the tendency to be due to some arcane principle of directed evolution (Orthogenetie PrinciPle) but an accidental by-product of the behaviors and actions required to satisfy new needs.Gradually perfecting and responding to new demands of the environment are therefore only two sides of the same coin. The fundamental difference between Darwin's and Lamarck's mechanisms of evolution is that Lamarck believed that the environment and its changes came first in order.They generate needs and activities in organisms, and then cause adaptive variation.In Darwin's case, random variation came first, and then the ordered action of the environment ("natural selection"); variation was not caused directly or indirectly by the environment. In order to provide a purely mechanistic explanation of evolution, Lamarck drew on the ideas of Caba-nis and other 18th-century physiologists, with the help of external stimuli and "elusive humors" arising from the satisfaction of new needs (subtle fluids) flow in the body put forward a well-conceived physiological theory.This physiological explanation comes down to Cartesian mechanism, which is of course completely inappropriate. Lamarck's ideas were rarely entirely new; all he did was codify them into new causal sequences and apply them to biological evolution.Yet no one has ever traced the origin of these ideas as persistently as he did.One of the basic points in Lamarck's theory is that the effort to satisfy needs plays an important role in changing the behavior and structure of individual animals; this view can be traced back to Condillac and Diderot. Condillac pointed out that the behavior caused by needs is a crucial factor in explaining the behavior of animals, and Diderot stated very briefly in "Le reve de DAlembert" (Le reve de DAlembert, 1769) that "Organs produce needs, and vice versa, Needs give rise to organs."This is exactly what Lamarck needed to explain the rise from a certain kind of creature to a more perfect kind of thought.He thinks this mechanism is so plausible and efficient that new organs could even be generated from it: "The formation of a new need for which a part is necessary does indeed bring about the existence of that part, which is the result of an effort to satisfy the new need." Even the higher taxonomic levels seem to be separated from each other by wide gaps, but this is only superficial, since "nature does not jump abruptly from one structural system to another." When discussing the When he presented the ten classes of invertebrates, he arbitrarily held that "races not only can exist, but can only exist near the border midway between two classes." If we cannot find these supposed intermediates , because they have not yet been discovered, because they inhabit remote corners of the world, or because our knowledge of "animals of the past" is still very limited.Lamarck seems to have come very close to the idea of ​​a common ancestry with regard to "animals of the past" and what he says of "animals of the present .He is content only to reveal a mechanism that can explain how the gaps between higher taxa are filled. Of course, the point of view of organs being used or discarded has existed since ancient times, and Lamarck gave a more rigorous physiological explanation for this point of view.And he also considered it one of the foundations of his doctrine, which he solemnly called his "First Law." "In every animal which has not yet passed its limit of development, the more frequent and prolonged the use of any one organ, the progressive strengthening, development, and enlargement of that organ will increase in proportion to the length of use. its above-mentioned power; such an organ, if it is not used for a long time, will be imperceptibly weakened and destroyed, gradually reducing its power, and finally disappearing." This principle of use and disuse is still prevalent in folklore, and we shall see It also had a certain influence on Darwin's thought. Another subsidiary principle of evolutionary adaptation is the inheritance of acquired traits. Lamarck systematized this into his "Second Law": "As a result of the influence of the environmental conditions in which animal species live for a long time, that is, as a result of the long-term use (or long-term disuse) of an organ, the Every character acquired or lost by an individual animal is transmitted by reproduction to the new individuals thus produced, so long as the acquired change of character is the same for both sexes, or is the same for all animals that produce offspring"( "Animal Philosophy"). Lamarck does not say by what mechanism (pangenesis?) the newly acquired traits are inherited.As Zirkle (1946) pointed out, this concept was generally adopted from antiquity until the nineteenth century, without Lamarck's additions.He just used it to serve the theory of evolution.Oddly enough, when Lamarckism was revived in the late nineteenth century, most people who had never read Lamarck in the original thought that Lamarckism was nothing more than a belief in acquired inheritance. Thus Lamarck was both blamed and credited for inventing a concept that was generally accepted in his time. Before concluding my account of Lamarck's model, I would like to emphasize that it does not include the two opinions usually ascribed to him.The first opinion is that new traits (new traits) are directly induced by the environment.Lamarck himself disputed this view ("Animal Philosophy"): Now I must explain what I mean when I say the following: The environment affects the shape and structure of animals.This means that when the environment becomes very different, it causes corresponding changes in the shape and structure of the animal over time. Indeed, if this statement were taken literally, I should be considered erroneous; for whatever the environment can do, it does not directly alter any shape or structure of the animal. (p. 107) Even though plants, as far as they are concerned, do not behave like animals, "and therefore have no habits of their own, great changes in environmental conditions can still cause differences in the development of their parts; and develop, while other parts weaken and disappear. But all this is caused by a change in the nutrition of the dry plant, due to the absorption of heat, light, air, humidity by the plant and the transpiration in the quantity发生变化所引起的。”换句话说，结构的改变是由于植物的内部活动相应于对环境的反应而引起的，就像植物趋光生长那样。 另一个错误地归之于拉马克的意见与意志的作用有关。拉马克着作的草率读者几乎一致地把一种意志学说（theofy of volition）诿之于拉马克：例如达尔文在写给J． D． Hooker的信中就曾谈到“拉马克胡说什么…适应出自动物迟缓的自愿”。产生这种误解的部分原因是由于将“besoin”这个字错译为“欲望”（“want”），而没有译成“需求”（“need”），并且忽略了拉马克精心推敲的因果链：由需求到努力到生理刺激到刺激生长到结构形成。拉马克还不会那样幼稚地认为基干愿望的想象能够产生新结构。 为了充分理解拉马克的思想，重要的是认清拉马克并不是活力论者，他只接受机械论解释。他也不是二元论者，在他的着作中从没有涉及物质与精神的二重性。最后，他又不是目的论者，并不承认进化是导向一个由上帝事前指定的目标。 对拉马克模式的详细分析表明这模式是极其复杂的。它运用了一些普遍承认的观点，如用进废退和获得性遗传，它对最简单的生物采纳了自然发生学说，就像任何人在任何一天能够证明从浸在水中的干草能产生纤毛虫一样（它完全接受了Spallanzani和Redi的自然发生对高等生物不适用的论据），并且运用了Canbanis及其它人关于被努力激起的难于捉摸的体液以及随之而来的对结构的影响之间的相互作用的生理学观点。拉马克的模式对一般人很有说服力，这些人就持有这模式所包含的大多数观点。这也就是为什么在出版了将近一百年之后拉马克的某些观点仍然继续广泛流行的原因。 关于拉马克是不是达尔文的“先驱”这个问题，长期以来一直争论不休（Baethelemy－Mydauly，1979）。达尔文本人曾经十分明确地否认他从拉马克的着作中得到任何教益，（这些着作）“确实毫无价值…我从中没有汲取到事实依据或有益的观点。”在他心境比较宽厚时他又说：“我得出的结论和他的结论相差并不太大，虽然进化的方式彼此全然不同。”（Rousseau，1969）为了有助于理解达尔文学说，下面先扼要介绍进化学说的一些组成部分。 进化的事实简单说来这里的问题是：世界是静止的还是发展进化的？纵然是提出展示本质的内在潜力的人最终也承认本质的一成不变性。拉马克学说与这些静止的或恒稳态学说截然相反。毫无疑问他作为采纳前后一贯真正进化演变学说的第一位学者是当之无愧的。拉马克还进一步提出了渐进进化并且以发展的均变论作为他的进化学说的基础。 在所有这些方面他毫无疑问的是达尔文的“先驱”。 进化的机制拉马克和达尔文在这个问题上的分歧最大。他们在这方面的唯一共同点是都承认用进废退这一软性遗传（Softinheritance）观点。这观点并非始于拉马克，达尔文则一般很少表露。 重点是多样性还是适应现象在进化论者之间有一个根本的他很少套到屋邂重视的意见分歧是，在他们看来究竟是多样性（物种形成）还是适应性（种系进化）重要。达尔文是通过物种繁衍的问题（如他在加拉帕戈斯群岛遇到的情况）来研究进化的。多样性的起源至少在刚开始时是他的主要兴趣。进化就意味着共同祖先。这就使得他们对进化的看法和种系进化论者的看法完全不同。 时间变化（纵向量纲）在达尔文主义者看来通常都是适应性的。拉马克从来没有明确地谈起适应概念，然而他所提出的进化的全部因果链必不可免地要归结为适应。由于他所描述的进化力不是目的论的而是机械论的，因而是通过自然方法或手段产生适应。 就达尔文学派来说，适应是自然选择的产物。就拉马克看来，适应是生物为了应付环境变化所必需的生理过程（连同获得性状遗传）的必不可免的产物。我看只能把他的学说指定为适应性进化。取得新的器官和新的能力显然是适应过程。如果承认他的前提，则拉马克学说就和达尔文学说～样，是名正言顺的适应学说。遗憾的是，这些前提后来被判明是无效的。 在长期被冷落并于1859年之后重新发现拉马克以来，“拉马克主义”这个词通常和信奉软性遗传相提并论。随着软性遗传被驳斥得更厉害，“拉马克主义”也愈加变成了贬义词。结果是拉马克作为一个卓越的无脊椎动物学家和开拓性系统学者所作出的贡献完全被忽视。同样被忽视的是他对行为、环境及适应的特别重视，生物学的这些方面几乎被当时的大多数动植物学家弃置不顾，这些动植物学家的分类学是纯粹描叙性分类学。 在拉马克以前没有任何一位学者像他那样确切地了解动物的大多数结构的适应性能，特别是纲和科的性状特征。拉马克将时间作为生命世界的量纲（因次，dimension）之一，这是前人从来没有做到的。 当辉格式文风在生物学史编篡中盛行的期间，拉马克的名字只是在谈到他的错误观点时才被提到，例如他相信软式遗传、内在完善性以及经由自然发生的物种形成。在他对理智所作出的重要贡献方面现在应当是为他恢复名誉的时候了。这些重要贡献是：他的严谨的进化论（genuine evolutionism），认为即使是最复杂的动物也是来自纤毛虫或蠕虫类祖先；他坚持均变论；他强调地球的悠久历史和进化的渐进性；他认识到行为和环境的重要性；他把人类放进进化潮流中去的大无畏精神。 要判断拉马克对随后进化思想的发展真正起到的作用是极其困难的（Kohlbrugge，1914）。他在法国几乎完全被忽视，但在爱丁堡（苏格兰）则受到Grant称赞并且由于莱伊尔（Lyell）的评论而在英国成为着名人物（也正是由于这评论而使得钱伯斯成为进化论者！）。但是在德国他的着作比在任何其它国家更受到重视，并被Meckel，海克尔（虽然他同时坚持自然选择观点）等人广泛引用。这些都有利于人们接受进化学说。 然而拉马克主义的普及最终倒成为障碍，它在1859年以后使达尔文的模式及硬性遗传几乎推迟了75年才被普遍接受。 拉马克的《动物哲学》宣告了进化学说的第一次突破。但是又经过了50年进化学说才被普遍接受。人们只能得出这样的结论，即17世纪和18世纪的神创论一本质论世界观还非常顽固有力不会在拉马克的富于幻想而又证据不多的思想观念前屈服。然而进化思想巨浪的存在却是无可怀疑的。化石记录的逐步完善，比较解剖研究的结果、生物地理学的兴起以及生物科学的许多其它进展都使得进化思想更加容易被人接受，但这并不是说这就使得拉马克的18世纪的解释进化机制的学说更容易被人接受。 因此，必须在接受进化学说和采纳某种解释其机制的特定学说之间严加区别。当我们深入到19世纪遇到对进化越来越多的解释时就尤为必要。在这些不同的学说中要弄清楚它们之间的区别并不总是容易的，因为某些学者往往将其中几个学说，或者至少是将它们的某些部分组合在一起。下面将最重要的进化学说列举出来并注明它们之间的区别。 从达尔文（或拉马克）时起一直到进化综合每种学说都有许多支持者。 大致有六种主要的学说（其中有一些还可以再分）；（1）趋向于日益完善的内在能力（自生学说，autogenetictheories）。这是拉马克学说的一部分。它得到下列学者的支持。如钱伯斯、内格里、Eimer（直生说，orthogenesis）、Osborn（优生说，aristosenesis）、以及Teilhard de Chardin（阿米加原则，Omega Principle）。 （2）用与不用的效应（用进废退），并与获得性状遗传结合。 （3）由环境直接诱导（拉马克反对，但杰弗莱支持）。 （4）骤变说（Saltationism，mutationism）。新种或更加少见（稀有）的模式的突然起源（莫培兑，Kolliker，高尔敦，贝特森，德弗里，Willis，Goldsehmidt，Schindewolf）。（5）随机分化，环境（直接或经由选择）或内部因素都不影响变异和进化的方向（Gulick，Hagedoorn，“非达尔文进化”）。（6）由自然选择支配的随机变异的方向或秩序（达尔文主义的一部分，新达尔文主义）。 学说（1）、（2）、（3）在拉马克以后的一百多年间得到了有力的支持。骤变说（4）目前已不被看作是物种形成的正常方式或任何其它新模式起源的正规途径。但是在特殊情况下（多倍体或染色体重排）却得到证实。目前对随机分化（5）能够达到什么程度有很多争议。然而目前几乎普遍认为大多数进化和变异现象都可以用学说（6）连同（5）加以解释。 这六种学说的支持者之间的争论往往被非生物学家误解为是对进化学说本身的有效性的争议。正是由于这个原因我于很早以前就注意到这些不同的解释学说的存在，虽则在拉马克之后的时期中主要的争论就是针对进化本身。事实上19世纪前半期所收集到的有利于进化的大多数新证据起初完全被忽视了。但是，对这些新事实的反应在法国、德国和英国就十分不同，这三个主要的欧洲国家都是致力于生物科学研究的。 为了反驳进化学说是启蒙运动中解放了的、唯物主义的、而且往往是无神论思想的直接继承的说法，对在这几个国家中事态发展的研究是特别重要的。事实并不支持上面的说法。可以这样说，启蒙运动随着法国大革命（1789）一起结束了，在随后的70年中，人们不仅见到了大量的反对意见（特别是在英国和法国），同时也看到了新的发展，这些新发展对于进化思想蔚然兴起的重要意义正不下于启蒙运动时期的哲学化。 拉马克去世后的四分之一世纪中法国博物学界显然是由居维叶左右着，虽然他只不过比拉马克多活了三年。当时只有着名的比较解剖学家杰弗莱（Etienne GeoffroySaint－Hilaire）表达了他的不那么正统的思想。在他的早期解剖学着述中完全没有用进化观点作出的解释。但是在1820年代的晚期，当他在研究法国北部Caen地区的佚罗纪的化石爬虫时惊奇地发现它们并不是他所想像的典型的中生代蛇颈龙（Plesiosaurus）一类的动物，而是和现有的恒河鳄（gavial）非常相近。这使得他认为侏罗纪的鳄类极有可能真正发生了转变，因为“环境完全有能力改变生物体。”他在1833年发表的一篇文章中进一步发挥了这种思想，他在文章中试图解释不同的动物为什么彼此不同，尽管“设计方案”是统一的。他企图借助于环境对呼吸的影响作出生理学的解释，因为环境对呼吸影响就要求“呼吸性体液”的环境发生剧烈变化，其结果就形成对生物体结构的巨大冲击或深刻影响。和拉马克相反，杰弗莱并不要求改变习惯作为改变生理的中间步骤。他认为环境可以直接诱导出结构的变化，而这种可能性是被拉马克断然否定的。虽然在18世纪末期新拉马克主义者（neoLamarckian）对直接诱导很重视，但是，如果像某些学者那样把这种假说定名为“杰弗莱主义”（Geoffroyism）倒更合适。按杰弗莱的意见，环境影响是在胚胎期实现，为了证实这论点，他用鸡胚为材料进行过广泛的实验研究。 有人认为杰弗莱在晚年转变成为了进化主义者，关于这个问题仍然有争论，Bourdier（1969）曾就此写过文章。杰弗莱并不承认共同祖先，但他认为由原始的物种通过不间断的繁殖所传下来的现存物种在这漫长的时期中通过外界影响已经发生了相当大的变化。 杰弗莱还具有进化论者感兴趣的一些其它想法。他认为由环境诱导产生的某些改变可能比其它改变更有用。发生有害变化的那些动物“将不再存在，而被其它的、形态结构发生了适合于新环境的变化的动物代替。”他在这里所谈的正是达尔文以前的淘汰学说（见下文）杰弗莱的进化推想没有产生持久的影响有不少的原因。杰弗莱是自然神论者，在宗教信仰上是保守的，他的学说并不是一种共同祖先学说，而是对既定模式现存潜力的激活的学说。他的某些言论也自相矛盾，由他提出的产卵的低等脊椎动物通过骤变转变成鸟类对进化潜力显露的学说毋宁是一种曲解。他为了使他的这一论点可信起见还谈起这种急剧变化（骤变）可以由环境的同等剧烈和急骤的变化所引起，这种说法也完全不能使人信服。 也许更糟糕的是杰弗莱的主要解剖学论点遭到了彻底失败，那就是将设计的统一方案扩展到整个动物界（参阅第十章）。 在前达尔文时期中（Pre－Darwinian period）没有人比居维叶（Georses Cuvier，1769－1832）提供了更多的新知识来支持进化学说。是他发现了（可以这样说）无脊椎动物的内部结构才将无脊椎动物学研究提升到新的基础上。是他创立了古生物学并且明确论证了巴黎盆地第三纪地层的各层都有特殊的哺乳类区系。更重要的是，他指明地层越深，其动物区系和现在的区系的差异就越大。他无可置辩地证明了灭绝现象，因为他所描述的已灭绝的长鼻类动物（象）不可能像所设想的海洋生物那样，在世界的某一偏僻地区存在而不被发现。他比其它任何人都更应该被看作是比较解剖学的创始人，一直到出版后他提出的比较解剖方法和原则都没有改动过。有了这样的背景和经历，人们一定会想到他会是完全正确的进化学说的第一位支持者，而实际上居维叶终其一生一直是完全反对进化观念的，而且他的论点对他的同时代人是如此具有说服力以致在他较早地去世后进化主义在下半个世纪在法国仍然无法立足。 是什么思想或事态促使居维叶如此顽固地反对进化学说？过去往往有人说他虔诚信奉基督教因而妨碍他相信生物进化，但是仔细研究过居维叶的着作后就否定了这种解释（Coleman，1964）。他在科学讨论中从来没有引用过圣经，而且他对过去历史的解释也经常和圣经不一致。例如他认为在摩西时代的那一次洪水之前还有过几次洪水，而且在地球历史的早期并没有动物。居维叶也从来不用世间的奇异事物来论证造物主的存在和仁慈（自然神学家就是如此）；他确实是非常谨慎地不把科学和宗教混在一起。他的有神论从来不闯进他的着作中，1832年4月5日的那一次着名的巴黎科学院辩论可能是例外。 另一种意识形态方面的原因似乎更重要。居维叶多情善感的青年时代是在斯图加特的卡尔斯学校度过的，因而沉浸于本质论中。这种影响在他随后研究动物分类时更行加强。和布丰、拉马克以及莱布尼茨的其它追随者不同，居维叶一直就强调不连续性。他将自然界阶梯分解为四个分支（门）就是他的态度的特点（参阅第四章）。他甚至坚持在四个分支中建立任何差异等级都是不可能的。其中每一个都包括四个纲，它们“都不成系列或不占有任何无可怀疑的等级”。即便一类中的某些成员可能显示较高的总体复杂性，但每一个结构并不一定都必然如此，一般来说很简单的生物有可能其某些结构是非常复杂的。居维叶并没有发现自然界阶梯的拥护者所宣称的“稳步提高复杂性或完善性”的任何证据。相反，他在每个地方所看到的倒都是不连续性和无规则的分化。 他的本质论反映在他的物种概念上（见第六章）。首先，他的物种定义使人感到是很符合生物学物种定义的：“物种包含一切双方产生、或从共同的父母产生的所有个体，还包含和它们相似正如它们彼此相似的那些个体。”但是他又反复强调只有表面性状（特征）是可变的。“在动物中还有一些（其它）性状抗拒或不接受一切影响，无论是自然的还是人为的影响，也无从证明时间较之气候或驯化对它们的作用更大。”居维叶还得意洋洋地指出，古埃及墓中木乃伊化了的动物已有几千年历史，它们和同一物种的现存个体完全没有什么差别。虽然他也意识到地理差异，他仍然强调这并不影响物种的基本特征：如果我们对野生食草动物的各种不同物种进行研究，并且将来自热带或寒带的个体，或来自食物贫乏或食物丰盛的栖息地区的个体加以比较，我们就会发现只有那些非本质特征如大小、颜色可能改变，而重要器官和体型关系的本质特征则一直保持不变。 实际上居维叶和其它巴黎科学院的成员一样对物种只有一点起码的兴趣。他是古生物学家和比较解剖学家，只关心主要类群，在他的研究工作中几乎从来没有真正的接触过物种问题。即使在他晚年研究鱼类时，他也从来没有从种群观点来看待它们。他根本没有研究过后来使达尔文和华莱士转向进化论的那些证据。 居维叶是强调地层系列中很多断裂（断层）是由于激烈变化所引起的第一个地质学家。他发现连续的动物区系可能先是海洋区系，后是陆地区系，然后又是海洋，再是陆地。显然海洋是反复入侵的；而且不仅是暂时性洪水。“因此我们被迫承认大海不只是在这个时期或那个时期淹没了整个大地，而且必定还长期以宁静的姿态滞留在那里。…海洋的这种反复进退既不是缓慢的，也不是逐渐的；大多数是灾变（居维叶本人在大多数情况下用的是比较温和的“变革revolution”这个词，但多数英译用了“灾变或灾祸——catastrophes”这字），发生得很突然；这很容易证实，特别是最严重的灾变。” 他随即引用在西伯利亚冰天雪地中发现的冻僵猛犸作为例子。“连同皮、毛、由一直保存到现在。如果它们死后不立即冻结，就会腐败而使尸体腐烂。”然而不仅动物区系证明了这种变迁的骤变性质，地质学也证明了这一点：“在以往的灾变中发生的地层断裂成碎片和地层整个颠倒过来已经足以说明这些灾变是突然而猛烈的，与最严重的灾变相仿。” 当时的化石记录有限，这有限的记录起初支持了下述结论：每次灾变都使发生灾变地区的所有动物区系遭到完全毁灭。没有任何物种的化石扩展到几个地层，至少对居维叶所熟悉的哺乳动物来说是如此。居维叶和Brongniart后来（1808）发现在同一岩层的连续层面上的动物区系变化是渐进的，主要差别是在某一特殊层面上最丰富的物种在两个相邻的层面上分布得不多或非常稀少。这一发现使得人们可以在相当远的距离内追溯地层。在居维叶的着述中曾暗示过他认为灾变多少是局部性的事件，这样有一些动物就可以从未受影响的地区移居过来。那时新发现的差异悬殊的澳大利亚动物区系支持了居维叶的观点，即完全不同的动物区系可以同时存在于地球上的不同地区。居维叶从来没有推测过灾变的原因，然而曾含蓄地表示灾变是像地震、火山爆发、大水灾、气候骤变以及造山运动（当时才开始被地质学家注意）等一类的自然现象。由之可以看出居维叶所说的灾变和他的追随者Buckland，dOrbignv以及阿伽西等所指的比较起来还是很“温和的”。 对居维叶来说，不连续性的普遍存在是和进化学说的解释完全不相容的。拉马克和杰弗莱借助于有规律地出现自然发生来解释不连续性。在居维叶看来，这和当时已有的一切证据都不相符。所有的事实都表明生物只能来自其它生物。哈维（Harvey）的名言“一切生命来自卵”（“Omne vivum ex ovo”）也是居维叶的座右铭。 更为重要的是，进化概念和居维叶的任何生物都具有协调的结构的概念是完全对立的。每一物种都是根据上帝的旨意创造的，从一开始就为它在自然界中指定了特定的、不能逾越的位置。例如鱼类就被指定给水域环境：“这是它们在创造中被指定的位置。 它们将居留在那里一直到事物的现存秩序遭到破坏为止”（《鱼类自然史》Histoirenaturlle poissons）。就居维叶来说，并不存在什么完备尺度（scale ofperfection），因为每种动物是完全适应于它在自然界中的特定场所的。如果他是达尔文同时代的人，他将会高兴地拥护达尔文的箴言“别说什么高级或低级！”这些想法促使他提出了他的着名（性状）相关原则（correlation principle，见第十章），根据这原则他概括出食草动物永远有蹄，食肉动物绝不会有角。只有形式（结构）与功能的某些特定的结合才是可能的，也只有这样的一些结合才能在自然界中实现。在居维叶看来，一种新习性能诱导出结构变化简直是不可想像的。特别是，他反对这种观点，即习惯变化后能够影响躯体的很多部分同时发生改变，却能保持一切器官的复杂而又协调的相互关系。另外，居维叶还认为结构的重要性高于功能和习性，只有结构改变了才可能要求功能也发生变化。 居维叶是一位卓越的博物学家不会不注意到变异现象，这就向他提出了如何调和他的本质论与这种认识之间的矛盾问题。他将变异性分为两个层次来解决这矛盾。一个层次表现为生物对诸如温度，营养物供应等环境因素的暂时性反应。这样的变异并不影响基本性状（特征），居维叶认为，如果用现代词汇来表示，则这种变异就是非遗传性的，也就是说它不影响物种的本质。他还认为最表面的性状是最容易发生变异的。 性质完全不同的另一种变异是重要器官，如神经系统、心、肺、内脏等的变异。按房维叶的意见，这些器官的结构在同一个纲和他所说的四大门中的同一类的动物中是完全稳定不变的。它们之所以必须稳定不变是因为任何一个主要器官的任何一种变异都将产生不平衡而导致严重后果。在稳定的性状中还包括区分物种、特别是化石物种与现存物种的性状。“由于这些化石物种与现在仍然存在的物种之间的区别被限制在一定限度内，我将指出这些限度比现在用来区分同一物种中的变种的要广泛得多，然后还要指陈这些变种受时间、气候或驯化的影响到什么程度”（《地球学说》，1813）。 任何研究都不支持居维叶所宣称的器官完全稳定不变以及它们在动物的较高阶元中所占的份量。如果这类研究是由唐维叶来进行，他将发现，和他所说的相反，在相近的种、属、科的动物中，其主要器官的相对大小和形状都有某些差异。然而即使他发现了这样的差异（就像他在解剖中所必然会发现的那样），他大概也会固执他的基本原则： 每个动物都是被创造来占有它在自然中所指定的位置。 居维叶的大多数议论都是专门针对拉马克和杰弗莱的进化学说而不是一般地反对进化主义。他特别反对拉马克常常含糊地提到的进化连续性。声称“现今世界上的某种动物是直接来自原始的该种动物，并且用事实或正当推理去证明它当然是必须做的，然而按现有的知识水平谁也不敢去尝试这样做”（1829）。在另一个场合他还说，“如果物种是逐渐改变的，那末我们就应当发现这类逐渐变化的某些痕迹；在古生物与现代物种之间我们应该找到一些中间过渡形式，然而这种情况迄今还并没有发生。”如果拉马克是一个重机警狡猾的对手，他就可能会指出一系列的第三纪软体动物来回答这一挑战。 就居维叶的化石哺乳类而言，则化石记录有限，当然是远远不能够构成一个系列来论证这一点，而且不少化石代表的是后来已经灭绝了的系谱的分支。拉马克当然不会利用这种论点进行辩论，因为他根本不承认灭绝现象。 居维叶在和杰弗莱以及自然哲学派的辩论中取得了胜利，因为他分清了有两种类型的相似。一方面是由于模式相同的相似（现在称为同源），另一方面还有另一种相似，例如蝙幅、鸟类、翼手龙、飞鱼的翼、这是由于功能相似。居维叶曾说：“如果鱼类和其它纲的动物在器官上有相似处，这只是指它们在功能上相似，这就是我们的结论。” The weird thing is.一遇到属于同一种解剖模式的动物时，例如不同种类的鱼，居维叶只强调它们的差异而完全忽视了显然并不是由于功能相同而形成的相似。他从不过问为什么同一模式的不同物种在基本结构上是如此相似。因而居维叶轻易地放过了对进化学说来说是强有力的比较解剖学上的证据。