For the proposition of evolution, there are only two basic questions: "change and invariance" and "if change, how to change". On the former question, Lamarck and Darwin have the same answer, but there are differences on the latter question, that is, their explanations of the change mechanism are different. Let's analyze the similarities and differences in details.
The conclusions of the two scholars come from the analysis and synthesis of factual materials, so we can assert that their conclusions are the result of careful consideration. 1799, Lamarck still indicated in the opening remarks of his course "Invertebrates" that the species remained unchanged, which was inherited from botanist De Yus and Linnaeus School. But then Lamarck showed his theory of evolution in his speech on May 1800+0 1 Sunday, which already included the basic ideas of his book Animal Philosophy (1809). Many historians who study Lamarck often ask themselves, what new discovery prompted Lamarck to accept this new view in 1800? According to the research of Burckhardt (1977), Lamarck took over the mollusk collection in the Paris Museum after his friend Bruggaier died in the late 1990s. When he began to study these collections, which included both fossils and modern mollusks, he found that many mussels were very similar to the existing and fossil species of other marine mollusks. In many cases, from the perspective of modern species, it is indeed possible to arrange early fossils and Neogene fossils in historical chronological order. In the case of fairly complete data, it can even be arranged in an almost uninterrupted pedigree. [5] It is this research that strengthens his evolutionary thought. During his voyage around the world, Darwin's research in biology and geology left a rich travel diary. Darwin's theory of evolution was initially formed when he sailed around the world in 1837, but he was serious about science and did not jump to conclusions. He insisted on continuing to possess a lot of facts and materials, and studied the variation under domestic and natural conditions, the occurrence and extinction of species, artificial selection and natural selection, and the difficulties in the theory of natural selection. You can see a wealth of examples from the Origin of Species. It was not until 1859 that he received a paper from biologist Wallace, which was consistent with his ideas, that he agreed to publish the Origin of Species.
As early as16th century, after the Renaissance, people began to accumulate quite a lot of factual materials in comparative anatomy, embryology, morphology and taxonomy, paleontological fossils and geology, etc. By Darwin's time, the proposition of species variability was irrefutable in the face of a large number of factual materials. However, there are obvious differences in mutation mechanism and evolutionary dynamics. On this issue, the only thing they have in common is Darwin's neutral attitude towards the inheritance of acquired traits: he explicitly mentioned "the habit and influence of organ use and non-use" in Variation under Domestic Conditions [1].
Lamarck acknowledged the universality of variation, but denied the randomness of variation: "Lamarck believes that the primary reason for evolution is to seek more complex (perfect) talents. When all kinds of animals are produced one after another, they naturally start from the most imperfect or simplest and end in the most perfect, which makes the structure of animals gradually complicated. This more complicated tendency comes from' the power given by God'. " [5] It can be seen that Lamarck believes that the change is directional and occurs out of some need. Darwin wrote in "Variation under Domestic Conditions": "Similar variation occurs under different conditions, while dissimilar variation occurs under the same conditions ... Under changing conditions, non-directional variation is more common than directional variation". He also wrote in "Variation under Natural Conditions": "Individual differences refer to many small differences between the descendants of the same parent ... Individual differences are very important, and they are usually heritable ... The most experienced naturalist will be surprised by so many examples of variation ..." [1] It can be seen that Darwin not only recognized the universality of variation, but also the randomness (non-directionality) of variation.
Both Darwin and Lamarck saw the role of environment in biological evolution, but Darwin and Lamarck held different views on the details of the relationship between environment and biology and the role of biology itself in the process of evolution. Lamarck believes that the second reason for evolution is the ability of organisms to respond to special conditions of the environment. Lamarck said that if the inner impulse to pursue perfection is the only reason for evolution, then there will only be a straight line sequence leading to perfection. However, in nature, we encounter various special adaptations of species and genera, rather than a straight line sequence. Lamarck believes that this is because animals must always achieve comprehensive coordination with the environment. When this coordination is destroyed, animals will re-establish a harmonious relationship through their behavior. [5] It can be seen that Lamarck believes that environmental change is the cause of evolution, but the main reason lies in the demand of organisms themselves: a demand that tends to be perfect. Let's take a look at Darwin's statement, in Variation under Domestic Conditions: "Living conditions change in two ways, acting on the whole mechanism or a certain part ... Compared with the nature of the organism itself, the nature of external conditions is secondary in determining the special type of each variation ... The variation that cannot be inherited is irrelevant, but the structural difference that can be inherited is immeasurable." In "Variation under Natural Conditions": "This variation seems to have nothing to do with living conditions ... it is useless to species ... the original species and varieties ... can be connected with any two types by a middle connecting rod ... If the variety is prosperous and exceeds the parent species, it will be regarded as a variety, and the parent species will be listed as a variety ... and may be replaced". [1] It is also mentioned that species changes destroy biological distribution, thus changing the environment and affecting competitive conditions. Obviously, Darwin's idea is to separate variation from environment. From this, we can see the fundamental difference in evolutionary mechanism between Darwin and Lamarck: Lamarck believes that the environment and its changes are orderly first, and they produce needs and activities in organisms, and then they undergo adaptive variation; Darwin believed that the first is random variation, and then the orderly activities of the environment (natural selection); Variation is not directly or indirectly caused by the environment.
For the motive force (or mechanism) of evolution, the difference between them is even greater. The basic view of Lamarckian theory is that the internal motivation of evolution is that "the efforts to meet the needs have changed the behavior and structure of individual animals", and "the formation of a certain part of necessary new needs has indeed contributed to its existence, which is the result of the efforts to meet the new needs". (< >) [5] The view that organs are used and discarded has existed since ancient times, and Lamarck gave a more rigorous physiological explanation to this view: in every animal that does not exceed the development limit, the more times any organ is used and the longer it lasts, the more it will gradually strengthen, develop and expand that organ, and it will also enhance its above-mentioned ability in proportion to the length of use. If such organs are not used for a long time, they will become weak unconsciously. [4] On the other hand, the inheritance of acquired traits: due to the long-term living environment of animals, that is, due to the long-term use (or long-term abandonment) of an organ, every trait that an animal individual gains or loses is passed on to a new individual through reproduction, as long as the changes of acquired traits are the same for both sexes, or for all animals that produce cubs (Philosophy of Zoology). [4] Lamarck did not talk about the mechanism by which the newly acquired traits were inherited, but a detailed analysis of Lamarck's evolutionary model showed that this model was extremely complicated, but he avoided the most important difficulties, but it was not rigorous. In contrast, Darwin's theoretical system of natural selection is very complete, and the controversy that may be harmful to his theory is not avoided in the Origin of Species. He proudly called his Origin of Species "a long debate", demonstrating two issues: "Species are changeable and then organisms evolve" and "Natural selection is the driving force of biological evolution". From the first question, we can clearly get the theory of "the same ancestor", which Lamarck ignores at the moment; The second problem is the theory of natural selection: over-breeding, survival competition, natural selection and survival of the fittest. At the same time, Darwin also mentioned three difficulties in theory: the first is the lack of transitional fossils; The second is that the long time of natural selection corresponds to the age of the earth; The third most fatal difficulty is that there is no reasonable genetic mechanism to explain natural selection. However, after a hundred years of research, the three difficulties have been well explained.
In the famous giraffe example, Lamarck explained the origin of giraffe's long neck in this way: giraffe's ancestors often craned their necks to eat leaves high in trees, and their necks were exercised and lengthened (used and discarded), which can be inherited and strengthened, so their offspring will be longer than their parents' necks (acquired trait inheritance), and giraffe's necks will get longer and longer from generation to generation. But in Darwin's view, the origin of long neck is not the result of waste, but the variation of long neck and short neck in giraffe ancestors (excessive reproduction, the source of variation). When the environment changes or food is scarce, the long neck has the survival advantage because it can eat leaves from higher places, and the short neck is gradually eliminated because of food shortage (struggle for existence). Due to the selection from generation to generation, the characteristics of long neck spread in the group.