Lamarckism is an evolutionary theory proposed by Lamarck and is based on two basic principles: the law of use and disuse and the law of inheritance of acquired characteristics.
→ Jean-Baptiste de Lamarck
Jean-Baptiste de Lamarck was born in Bazentin, France, and died in Paris. He began his career as a botanist, but has worked in several other areas, with emphasis on Invertebrate Zoology, Paleontology and Evolution. This famous researcher was one of the founding professors of the Musée National d’Histoire Naturelle and carried out several works on worms and spiders. He published his ideas on evolution in 1809, in a work entitled Philosophie Zoologique .
→ Lamarck’s ideas
According to Lamarck’s hypothesis, organisms became increasingly complex individuals as a result of the pressure of the environment, which forced them to change. These changes were, therefore, due to the needs of individuals. The way in which these changes would occur was based on two basic principles: the law of use and disuse and the law of inheritance of acquired characteristics.
- Law of use and disuse – This principle states that parts of the body that are used frequently become stronger and more developed, while those that are infrequently used atrophy.
- Law of Inheritance of Acquired Characteristics – According to this principle, characteristics acquired during an individual’s lifetime could be passed on to their offspring.
→ The example of the giraffe
One of the classic examples used to explain Lamarck’s ideas is the case of the giraffe’s neck. According to the ideas proposed by Lamarck, the giraffe’s neck became long as a result of the need to reach leaves on the higher branches.
According to this biologist’s ideas, giraffes stretched their necks in order to get food, making this part of the body stronger and bigger ( law of use and disuse) . These changes, according to Lamarckism, were passed on to descendants ( law of inheritance of acquired characteristics). This caused the descendants to present, over time, larger and larger necks as they continued to exert themselves, and these changes continued to be passed on.
→ Errors of Lamarckism
Although Lamarck realized that the environment exerted an influence on the species, he could not explain how this happened. Of course, Lamarck did not have the knowledge about genetics that we have today, a fact that ended up resulting in flaws in his ideas.
We currently know that, although we can develop some structures through their use, as is the case of increasing muscle mass, we cannot pass this characteristic on to our descendants. In addition, we also know that evolution does not follow a straight line that leads to the complexity of living beings, that is, evolution does not occur with the aim of making organisms better and more complex.
→ Lamarckism and Darwinism
Lamarck presents ideas quite different from those proposed by Charles Darwin. Among these differences, we can mention that Darwin did not say that organisms naturally evolve towards complexity, that is, the organism does not evolve in search of improvement. Darwin even mentioned that species can often become extinct during this process. The central idea of the theory proposed by Darwin is that of natural selection, which explains that the environment selects the fittest organism. However, although there are differences, we cannot forget that Darwin accepted some of Lamarck’s misconceptions, as he believed in the law of inheritance of acquired characteristics.