Jean-Baptiste Lamarck (1744 – 1829) is one of the best-known and most studied naturalists, not least because his theory on the evolution of lineages brought us closer to what we now know about biology.
And although it is true that his contributions to science are usually eclipsed by Charles Darwin’s ideas, it is worth knowing, even if only minimally, his intellectual legacy.
In this article you will find in summary form an explanation about Lamarck’s theory.which was centered on a concept called “inheritance of acquired characters”.
What is Lamarck’s theory?
The first thing to know about Lamarck’s theory is that, while it was an important milestone in the scientific development of humanity, is no longer valid todayand is considered to be of interest as an object of study of history and social sciences.
This is because while his ideas inspired the researchers who would later lay the foundations for 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, bearing in mind 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 tried to explain the evolution of species through the following hypothetical process, which we will see explained with the example of giraffes.
1. Struggle for survival
Individuals are forced to adapt to the environment in which they live, or they will die.. For example, a population of artiodactyl ancestors of giraffes needs to adapt to a very dry ecosystem with few plants.
2. Developing 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 between birth and death).
In the case of the previous example, the ascendants of the giraffes stretch their necks as far as possible to reach the branches of the tallest trees, which are beyond the reach of other herbivores. This makes those who do it better have their necks a little longer..
3. Increased 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, the artiodactyls that have managed to lengthen their necks have more chances of surviving and having 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 ones.
Speaking of the example we are working with, neck lengthening becomes part of the innate characteristics of the next generation, being “fixed” in its morphology from the beginning. This way, these new individuals leave with advantage at the time of competing to have a longer and longer neck as did the members of the previous generation.
Their differences from Darwin’s theory
As we have seen, Jean-Baptiste Lamarck devised an interesting theory combining phylogenetic processes (i.e. relating to the evolution of lineages across generations) with ontogenetic processes (relating to the changes each individual undergoes throughout his or her life development).
How do the ideas of this French naturalist differ from those of Charles Darwin, which would emerge a few decades later?
The main difference between Lamarck’s and Darwin’s theory is that the latter does not emphasize the individual history of individuals as part of their struggle for survival.
For the English, it was not so important the effort or the way in which individuals chose to find a livelihood and protect themselves; what was important to him was the result of all this: whether to leave offspring or not. And this was so because Darwin already assumed that there were individual differences between the members of a speciesThese differences were independent of willpower or survival techniques learned by individuals throughout their lives.
Thus, Darwin proposed that as a result of these existing individual differences before trying to learn to survive and inherent to all populations in the same species, certain individuals had more reproductive success than others. If for Lamarck different actions served to develop different organs, for Darwin the order was the inverse: 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 traits, and in fact he believed in pangenesis, a theory with very ancient roots according to which both cells and gems 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 foundations 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 together, there are many differences that are worth taking into account.
First of all, Lamarck’s theory is 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 of something, but a field of biology that scientists continue to study today.
In other words, epigenetics is not a proposal to describe 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, modern evolutionary synthesis) is an explanation that tries to adjust as best as possible to that facet of nature.
And what exactly does epigenetics consist of? This is a series of mechanisms by which the interaction between the environment and organisms causes genes to express in one way or another. It realizes the fact that the phenotype of all forms of life is not expressed in a unidirectional way, but that in it the interaction with the environment also influences.
This general idea of gene expression should not be confused with the ideas held by Lamarck. Specifically, this French naturalist emphasized the concept of the transmission of acquired traits from one generation to another, and could not even conceive of the idea of how genes are expressed, because at the 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 traits, 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 trait development through interaction with the environment is not taken).
Bibliographic 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.