Darwinism: Two major factors mentioned in Darwinism are the battle for life and survival of the fittest. Lamarckism: Lamarckism does not recognize struggle for life and survival of the fittest. Darwinism: Only useful variations will be translated over successive generations, according to Darwinism.
Lamarckism: Lamarckism proposes that the next generation inherit all of the acquired characters. This theory was anticipated by Jean Baptiste de Lamarck. This theory was anticipated by Charles Darwin. Individual population has identical characteristics. Individuals can make a difference. The interbreeding population of individuals always has similar characteristics with certain variability.
Individuals are eternal. The population will turn itself. Internal drive towards greater complexity, influenced by the inheritance of properties acquired.
Variations are tailored to the needs of the organism. Variation does exist regardless of the condition of the organism. Eg: The long neck of a giraffe. This has led biologists to re-launch the debate on a possible update of this one.
Some even go so far as to mention the need for a synthesis between the two theories. We will see that the considerable differences between them do not argue in favour of such an idea.
This subject will be treated here from the strict biological point of view, by comparing the basic principles of these theories and the visions of the living world that flow from them, particularly on the origin of life and on the mechanisms of transformation of species.
An article by Laurent Loison and Francesca Merlin, which addresses this problem from the perspective of the history and philosophy of science, can also be found in the Encyclopaedia Universalis [3].
It should be noted in passing that in the light of our current knowledge on the extraordinary complexity of the most elementary living cells and on the origin of life, this idea of permanent spontaneous generation makes people smile. Lamarck imagines that these primitive organisms gradually become more complex over the course of geological time to reach all existing living beings. A complexity that is synonymous for him with perfection and which would result from an inherent property of the living beings to which we will return later.
Figure 3. Representation of phylogeny of animal species according to Lamarck. On the right, representation of the evolution of living organisms over time. Appeared by spontaneous generation, organisms become more complex over time. There is no filiation between two distinct lines. Thus, since the origin of the planet, the simplest organisms would spontaneously appear from the inert matter and would repeatedly initiate series that would evolve in parallel Figure 3.
Within each of these lines, filiation exists, from the simplest to the most complex, but there can be no genealogical relationship between the lines. Lamarck also postulates that primitive plants and animals appear in two independent ways. It also allowed two separate routes for animals. In short, in Lamarckian theory, the living world would be composed of multiple successive and independent lines.
There would be no single common ancestor. Darwin, for his part, does not speak of the appearance of life in The Origin of Species , except to say that the knowledge of his time did not allow him to approach it. It is sometimes mentioned in his correspondence, notably in a letter from to his best friend Joseph Hooker.
But if and oh! Figure 4. Darwin describes very clearly here his ideas on the appearance and extinction of species. He refuses the idea of permanent spontaneous generation, which has been universally accepted since Pasteur [4].
As a result, all living beings on the planet are derived from this ancestral form of life Figure 4. Figure 5. This vision is fully in line with modern scientific research that is trying to understand the characteristics of this primordial ancestral form, called LUCA for Last Universal Common Ancestor Figure 5.
There are at least two other important differences between these theories. As they both concern the modalities of evolution, they are very intertwined; but for the sake of clarity we will present them separately. We are entering into what is really the heart of the two theories. In plants, Lamarck is led to propose an even more direct influence of the environment on the organism because, of course, we cannot talk about efforts and habits in plants!
In his theory, variations are therefore always induced, more or less directly, under the influence of external conditions. Since the discovery of genetic mutations at the beginning of the 20 th century, neolamarckians have had to integrate the idea that these mutations are at the root of variations.
They then imagined that they had to be directed by the environment, on specific genes, to adapt the organism to its environment. But this idea is in contradiction with all the experimental research carried out since the s. The most recent and one of the most demonstrative was published in by an American team [6]. We will come back to this later.
Based on these induced variations, the transformation of species would be driven by a trend towards increasing complexity, at least in animals. But where would this trend come from? It would be an immanent property of living beings that irreversibly pushes them towards ever greater complexity.
It is therefore a law of nature that requires no explanation. It should be noted in passing that, in the same logic, Lamarck did not believe in the extinctions of species, except those destroyed by human actions.
For him, species are transformed by becoming more complex but do not become extinct. Lamarck, however, wanted to be very materialistic and often repeats that the living obey only physical laws. It should be noted that this trend towards complexity, as well as the influence of the environment on changes, both function as an anti-hasard. The share of randomness in the transformation of species is therefore limited in Lamarck.
Charles Darwin is a naturalist and an Englishman. His main work lies in the theory of evolution which he told that species have their own common ancestors, and that evolution resulted in natural selection. Later, people and the scientific community accepted his study as a fact.
Jean Baptiste Lamarck, on the other hand, is French. He was a former soldier and then went to becoming a naturalist, a zoology professor, and a botanist.
The latter book was about the classification of invertebrates in which he was the first to coin such a word. He worked on further and focused his studies about invertebrate zoology. Lamarck believed that species evolved due to acquired characteristics in response to the drive of the environment.
For example, he believed that giraffes really do not have long necks. But since these animals are trying to reach for food by stretching their necks, their next offspring had longer necks and were able to reach food. On the other hand, Charles Darwin believed that all species came from a single ancestor. He believed that there were types of giraffes with longer necks and with shorter necks.
However, those giraffes with shorter necks died due to competition and the drive of the environment, and those with longer necks survived.
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