Lamarck’s Theory of Acquired Characteristics Definition
Jean Baptiste de Monet (1744-1829), universally known as “Lamarck”, was the first to expose a scientific theory about evolution, which he did in his book “Zoological Philosophy” (1809).
This theory, known as the “Theory of acquired characters”, “Transformism”, or simply “Lamarckism”, is the first theory of evolution and in it, Lamarck concretizes the ideas put forth by the first evolutionary scientists, such as Erasmus Darwin ( Charles Darwin’s grandfather) or Georges-Louis Leclerc (Count of Buffon), and uses his observations on fossils and current animals and plants to shape an entire theory with a broad scientific basis.
Said theory includes as essential ideas the following:
***Living beings can undergo changes throughout their lives to adapt to the changing or new circumstances of the environment in which they live (that is, living beings evolve).
***These changes are acquired characters, since they are not inherited from the parents, and originate from the continued use or disuse of certain organs or parts of the body throughout life.
***These new characters are transmitted to the offspring and are perfected over generations.
As we know, this theory turned out to be erroneous, being its error more evident the idea that the characters acquired along the life can be transmitted to the descendants. Lamarck thought that this could happen in nature as a result of the need for organisms to improve and improve their chances of survival when their environment changed. This vital requirement was the one that forced nature to conserve those changes achieved with so much effort. It did not seem logical that the characters acquired to survive and adapt to the environment were lost and the natural cycle had to start again, because in this way the variations between individuals would never be consolidated and the idea of evolution would be in an alley without exit.
Thus, the need to reach the food that was increasingly higher caused certain animals were stretching their neck throughout their lives, to reach the leaves of trees. This lengthening of the neck (an improvement caused by the need to survive, that is, an acquired character) was transmitted to their descendants, otherwise they would not have survived. Thus, after many generations, these animals ended up creating the current giraffes. That is, natural conditions forced living beings to change and inherit those changes.
His theory was almost as harshly criticized as Darwin’s was later.
The most prestigious scientist of his time, the paleontologist Georges Cuvier, convinced creationist and author of the theory of catastrophism, conducted numerous experiments on animals to show that acquired characters were not inherited. For example, if the tail was cut to mice for several generations, these animals continued to produce offspring with tails.
These evidences contributed by Cuvier annihilated Lamarck’s theory and his prestige as a scientist, to such an extent that since then he fell into oblivion and did not publish any scientific work until his death, which came to him in the most absolute poverty and forgotten by the scientific community
However, the idea that living beings change remained in the air … and in the minds of other naturalists who read his work, so it was only a matter of time before a new and more complete theory appeared, as happened 30 years after his death, with the publication of “The origin of species.”
But the “Zoological Philosophy” is not his only important work. Lamarck was a great taxonomist, as he demonstrated in his book “Flora of France”, in which he used dichotomous keys for the identification of plant species.
He also published a monumental work, “Natural history of invertebrate animals”, in 7 volumes, where he coined the then new term “invertebrates”. Likewise, Lamarck was the first to use the term “Biology” for the life sciences, a term that would not end up being imposed until much later.