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The Lamarck Theory and the evolution of the species

The Lamarck Theory and the evolution of the species

April 29, 2024

For centuries, the question of how different forms of life have been emerging has been a question that has fascinated humanity. Myths and legends have been created around this question, but more complete and systematic theories have also been developed .

The Lamarck's theory It is one of the most famous attempts to propose an idea of ​​the evolution of species in which there is no divine intelligence to direct the process.

Who was Lamarck?

The person who proposed what we know today as Lamarck's theory was Jean-Baptiste de Lamarck , was a French naturalist born in the year 1744. In his time, the study of living beings was a totally different discipline than what is today biology, and that is why it held ideas about the functioning of the natural processes in which the divine intervened, something that would be scandalous by current scientific standards.

Lamarck made biology largely independent of religion proposing a theory of evolution in which the intelligences of the beyond had no role .

What was Lamarckism?

Before the English naturalist Charles Darwin proposed the theory of evolution that would forever change the world of biology, Lamarck's theory already proposed an explanation about how they could have been appearing different forms of life without having recourse to one or several gods.

His idea was that although the origin of all forms of life could be created spontaneously (presumably by direct work of God) but that, after this, evolution was produced as a product of a mechanical process resulting from the physical and chemicals of matter with which organisms are formed and their environment.

The basic idea of ​​Lamarck's theory was the following: the environment changes, the ways of life struggle to adapt continuously to the new demands of their habitat , these efforts modify their bodies physically, and these physical changes are inherited by the offspring. That is to say, that the evolution proposed by Lamarck's theory was a process that is sustained in a concept called inheritance of acquired characteristics: parents transmit to their children the traits they acquire from how they relate to the environment.


We know how this hypothetical process worked, using the most famous example of Lamarck's theory: the case of giraffes that stretch their necks.

The example of giraffes and Lamarck

At first, an animal similar to an antelope sees its surroundings becoming increasingly dry, so that grass and shrubs become increasingly scarce and need to resort to feeding on the leaves of trees more frequently . This makes stretching the neck to become one of the defining habits of the day to day life of some of the members of their species.

So, according to Lamarck's theory, the pseudo-antelopes that do not struggle to access the leaves of the trees by stretching their necks tend to die leaving little or no offspring, while those who stretch the neck not only survive since having the neck stretched is prolonged, but this physical feature (the longer neck) is transmitted to their heritage.

In this way, with the passage of time and generations, a way of life that previously did not exist appears: the giraffe .

From simplicity to complexity

If we go from the first plane that involves describing the process by which one generation passes on its acquired characteristics to the next, we will see that the explanation by which Lamarck's theory tries to account for the diversity of the species is quite similar to the ideas of Charles Darwin.

Lamarck believed that the origin of the species was embodied in a very simple way of life that generation after generation was giving way to more complex organisms. These late species carry traces of the adaptive efforts of their ancestors , with which the ways in which they could adapt to new situations are more diverse and gives way to more variety of life forms.

What does Lamarck's theory fail?

If Lamarck's theory is considered an outdated model it is, first of all, because today we know that individuals have a limited margin of possibilities when it comes to modifying their body with its use. For example, the collars are not lengthened by the simple fact of stretching, and the same happens with the legs, arms, etc.

In other words, the fact of using a lot of certain strategies and parts of the body does not make them adapt their morphology to improve compliance with this function, with some exceptions.

The second reason why Lamarckism fails is because of its assumptions about the inheritance of acquired abilities. Those physical modifications that do depend on the use of certain organs, such as the degree of bodybuilding of the arms, they are not transmitted to the offspring , automatically, since what we do does not modify the DNA of the germ cells whose genes are transmitted during reproduction.

Although it has been proven that some forms of life transmit their genetic codes to others through a process known as horizontal gene transfer, this form of genetic code modification is not the same as that described in Lamarck's theory (among other things because at the time the existence of genes was not known).

In addition, a type of genes whose function is to restart the epigenome of the life forms that are being created in their zygote phase , that is, make sure that there are no acquired changes that can be inherited by the offspring.

The differences with Darwin

Charles Darwin also tried to explain the mechanisms of biological evolution, but unlike Lamarck he did not limit himself to placing the inheritance of acquired characters at the center of this process.

Instead, he theorized about the way in which the pressures and demands of the environment and the ways of life that coexist with each other mean that, in the long run, certain traits are passed on to the offspring with a higher frequency than others , which over time would make a good part of the individuals of the species, or even almost all of them, end up possessing that characteristic.

Thus, the progressive accumulation of these changes would cause different species to be created over time.

The merits of Lamarckismo

The fact that this naturalist rejected the idea that miracles have an important role in the creation of all species made Lamarck's theory about evolution ignored or belittled until the moment of his death. Nonetheless today Lamarck is very recognized and admired not because his theory was correct and to explain the process of evolution, since Lamarck's theory has become obsolete, but for two different reasons.

The first is that the way in which Lamarck conceived evolution can be interpreted as an intermediate step between classical creationism according to which all species have been created directly by God and remain the same throughout generations, and Darwin's theory , basis of the theory of evolution that is the current foundation of the science of biology.

The second is, simply, the recognition of the difficulties that this naturalist had to face when devising and defending Lamarck's theory of evolution in its historical context at a time when the fossil record of life forms was scarce and it was classified in a chaotic way. Studying something as complex as biological evolution is not easy, because this requires analyzing in detail very specific aspects of life forms and build with it a highly abstract theory that explains the kind of natural law that is behind all this kind of changes.


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