This theory, already outdated, explained the evolution of species based on their adaptation to the environment.
Jean-Baptiste Lamarck (1744 – 1829) is one of the most well-known and studied naturalists, not least because his theory of lineage evolution brought us closer to what we know today about biology.
And although it is true that his contributions to science are often overshadowed by the ideas of Charles Darwin, it is worth knowing even minimally his intellectual legacy.
In this article you will find in summary an explanation about Lamarck’s theory, which was centered on a concept called “inheritance of acquired characters”.
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What is Lamarck’s theory?
The first thing to know about Lamarck’s theory is that, although it was an important milestone in the scientific development of humanity, today it is not valid, and is considered to be of interest as an object of study in history and the social sciences.
This is because while his ideas inspired researchers who would later lay the foundations of the current theory of evolution, Lamarck’s ideas were based on many erroneous beliefs about the interaction between organisms and their environment and about the transmission of traits from one generation to another. Something natural, considering that in his time there was not even a theory that unified the field of study of Biology as a science.
But let’s cut to the chase: what did Lamarck’s theory say about the evolution of species? Basically, Lamarck was trying to explain the evolution of species through the following hypothetical process, which we will see explained with the example of giraffes.
1. Fight for survival
Individuals are forced to adapt to the environment in which they live, or they will die. For example, a population of giraffe ancestral artiodactyls needs to adapt to a very dry ecosystem with few plants.
2. Development of new traits through effort
Some individuals develop new traits and characteristics as a result of the literal effort to achieve their survival goals (within their ontogenetic development, that is, individually and in the time that passes between birth and death).
In the case of the example above, giraffe ancestors stretch their necks as far as possible to reach the branches of taller trees, which are out of reach of other herbivores. This makes those who do it better lengthen their necks a little.
3. Greater reproductive success
Those who manage to survive as a result of the acquisition of these traits are more likely to leave offspring. In this case, artiodactyls that have managed to lengthen their neck have more options to survive and have more offspring.
4. Inheritance of acquired characters
At this stage, the offspring receive these traits acquired by their ancestors through biological mechanisms (through what happens in gestation), not cultural.
Speaking about the example with which we are working, neck lengthening becomes part of the innate characteristics of the next generation, being “fixed” in its morphology from the beginning. In this way, these new individuals start with an advantage when competing for a longer neckjust as the members of the previous generation did.
Differences from Darwin’s theory
As we have seen, Jean-Baptiste Lamarck devised an interesting theory in which phylogenetic processes (that is, relating to the evolution of lineages through generations) are combined with ontogenetic processes (relating to the changes that each individual undergoes throughout their life development).
How do the ideas of this French naturalist differ from those of Charles Darwin, which would emerge a few decades later?
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The main difference between Lamarck’s theory and Darwin’s theory is that the latter places no emphasis on the individual history of individuals as part of their struggle to survive.
For English, the effort or the way in which individuals chose to find a livelihood and protect themselves was not so important; And this was becauseDarwin already assumed that there were individual differences between the members of a species, differences that were independent of willpower or survival techniques learned by individuals throughout life.
Thus, Darwin proposed that as a result of these individual differences existing before trying to learn to survive and inherent in all populations in the same species, certain individuals were more successful reproductively than others. If for Lamarck different actions served to develop different organs, for Darwin the order was the reverse: organs with unique characteristics created new actions and models of adaptation.
In any case, Darwin did not entirely reject the idea that biological evolution could be explained in part through a mechanism of inheritance of acquired characters, and in fact he believed in pangenesis, a theory with very ancient roots according to which both cells and genemules participate in the gestation of new generations. Hypothetical entities that would circulate through the organism and collect information on the influence of the environment on the organism.
What happens is that Darwin laid the foundation for the development of a scientific theory much more parsimonious than Lamarck’s, that is, one that needed fewer presuppositions to be sustained.
Is Lamarckism the same as epigenetics?
In recent times it is relatively common for Lamarck’s theory to be associated with epigenetics. While there are certain aspects between these two concepts that fit, there are many differences worth considering.
First, Lamarck’s theory is just that: a scientific explanation (in the context in which it arose) about a series of phenomena. Epigenetics, on the other hand, is not an explanation about something, but an area of biology that scientists continue to study today.
That is, epigenetics is not a proposal for description of a natural phenomenon, but is one of the natural phenomena to be explained, in the same way that the evolution of species is a reality to be understood through scientific knowledge and the theory of evolution (or rather, the modern evolutionary synthesis) is an explanation that tries to adjust as best as possible to that facet of nature.
And what exactly is epigenetics? It is a series of mechanisms by which the interaction between the environment and organisms cause genes to express in one way or another. It accounts for the fact that the phenotype of all life forms is not expressed in a unidirectional way, but that interaction with the environment also influences.
Now, we must not confuse this very general idea about the expression of genes with the ideas held by Lamarck. In particular, this French naturalist emphasized the concept of the transmission of acquired traits from one generation to another, and could not even conceive the idea of how genes are expressed, because in his time the gene was a totally unknown entity.
The only relationship between epigenetics and Lamarck’s theory is that the latter speaks of the influence of the environment on the traits of the individual, although it does so by appealing to mechanisms of “fixation” of characteristics in family lineages, and today we know that these mechanisms do not exist.
The closest thing to this cannot be considered inheritance of acquired characters, and is the horizontal transmission of genes that occurs basically in the microscopic world, by which one organism passes chains of genetic material to another (and therefore the intermediate step of developing traits through interaction with the environment is not given).
References
- Dawkins, R. (2005). The Blind Watchmaker. Barcelona: Tusquets.
- Packard, A.S. (2016). Lamarck, The Founder of Evolution. Palala Press.
- Ruse, M. (1999). The Darwinian Revolution: Science Red in Tooth and Claw. Chicago: University of Chicago Press.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.