The first comprehensive theory of evolution was proposed by Jean-Baptiste Lamarck. The contribution to the biology of the scientist was based on thoughts and principles that already existed in the scientific community of that time. The most important of them was the idea of scala naturae, as well as the idea that species can change in different environments.
Scala naturae, the “great chain of being," dates back to Aristotle and probably to an earlier period. This is a hierarchical classification system, in the lower part of which are the simplest organisms, and at the top - the most complex.
Ideas about changing species at the beginning of the 19th century were quite common - they did not become a breakthrough of Lamarck. For example, Buffon, his mentor, expressed his own ideas on this subject, although they were all very vague.
The path to biology
Lamarck went to science on a bumpy path, serving in the army for a long time, and studied medicine for four years, before his brother talked him out. He became a student of the leading French naturalist Bernard de Jouet, focused on botany, and in 1978 published a three-volume collection of French flora, which was impressive enough to attract the attention of Buffon, who took it under his wing and secured a place in the French Academy of Sciences and the Royal Botanic Gardens . After the French Revolution, the gardens were transformed in 1793 into the National Museum of Natural History, in which Lamarck was promoted to professor of invertebrates (despite the fact that this was not his specialty), which he held until his death.
The merits of Jean-Baptiste Lamarck in biology are not limited to the theory of evolution. Many of his achievements are taken for granted - the word “biology” is his invention, as are the systematic categories of “vertebrates,” “invertebrates,” “insects,” “carapace,” “arachnids,” “echinoderms,” and annelids.
The doctrine of Jean-Baptiste Lamarck was presented in three publications. He became interested in evolution, sorting at the Museum of Natural History a collection of fossils and modern mollusks of Brugier, the previous curator of exhibits in the invertebrate department. Lamarck noticed that they were similar, and, postponing their distribution in time, he could trace a straight line from ancient samples to the latest. This triggered other thoughts that he set out in his 1801 book, Studies of the Organization of Living Bodies.
Jean-Baptiste Lamarck: a contribution to biology
But the real details of the explanation of the evolutionary process appeared in his main work of 1809, The Philosophy of Zoology. In 1815, the first volume of the textbook, The Natural History of Invertebrates, was published, which also presented the ideas of Lamarck.
The concept of the “great chain” has become the cornerstone of Lamarckism. But he went further than his contemporaries, trying to justify its mechanism, and not to take it for granted. He suggested that animal life contains a built-in ability, innate quality becoming more complex, which would explain the existence of a natural hierarchical classification. This can be illustrated not as climbing stairs, but as moving on an escalator.
But then the creationists classic argument arises: if we evolved from apes, then why do apes still exist? The solution is that biogenesis - the formation of a new life - is ongoing. In other words, there are many escalators (one for each category of life), each of which has its own starting point. Humans are the oldest organisms, and worms are the newest.
But there is a second problem. Hierarchical classification, such as "worms-fish-reptiles-birds-mammals-primates-humans" for, for example, felids does not work. At this level, hierarchy becomes a meaningless exercise, and here the most famous part of Lamarckism appears: the inheritance of acquired characteristics. This concept is simple.
Giraffe lives in a savannah with tall trees. This induces a “need” for the giraffe, and it changes its behavior to reach higher branches. According to Lamarck, this additional use of the neck will lead to its growth due to the increased flow of “vital fluid”. A new neck condition is an acquired characteristic, and it can be passed on to offspring, which is why we are talking about the inheritance of acquired characteristics.
The converse is also true: if the organ is not used, then the fluid flows through it less, and it atrophies. For example, this explains why cave dwellers have no eyes.
Inheritance of acquired characteristics
Another example is the membranes between the fingers of many waterfowl such as frogs, sea turtles, otters and beavers. To swim, animals need to push water, which is due to the membranes, as a result of which they get more “vital fluid”, as Jean-Baptiste Lamarck believed.
The contribution to the biology of the scientist includes the basic concept of the inheritance of acquired traits. This did not become a physiological discovery (“vital fluid” was never discovered). It was a purely naturalistic and mechanistic view, which at that time turned out to be revolutionary. There was no longer a need for God as the leader of evolution. The concept also went against the idea that organisms can only change in a certain way.
Thus, there are two fundamental principles of Lamarckism. The first of these is the idea of natural, linear progress on a complexity scale. However, the path to excellence is extremely winding: organisms adapt to local conditions, which led to a variety of forms even at the same level of complexity.
Knowing what Lamarckism is, one can critically evaluate the pros and cons of Jean-Baptiste Lamarck as a researcher from a modern point of view.
Any philosopher of science will say that setting the right tasks and correctly asked questions make up half of scientific research. It was in this respect that Jean-Baptiste Lamarck distinguished himself: his contribution to science was that he understood four main problems of the natural history of that time:
- Why are fossil forms different from those that have come down to us?
- Why are some organisms more complex than others?
- Why is there so much diversity?
- Why are organisms well adapted to their environment?
The disadvantages of Jean-Baptiste Lamarck are that he failed to provide any correct explanation, although not through his own fault. Anyone in his place would stop at a similar set of ideas, and not at natural selection or mutations.
Jean-Baptiste Lamarck: Errors of Theory
Lamarck argued that fossil forms are different because they, as they climbed the escalator of evolution, are replaced by more complex ones. Now we know that fossil forms belong to different parts of phylogenesis, and therefore are different.
There is no such thing as a scale of complexity. Complex forms arise in individual taxa as a result of their unique circumstances. The most typical example of complexity - multicellularity - is unique and is not the result of a common trend.
Diversity is not a product of constant biogenesis. Everything points to the only source of life. Variety is the result of speciation.
There is no such thing as a "vital fluid." Organisms are adapted to their environment, as they passed through the inexorable millstones of natural selection.
In natural selection, as it is understood today, the entire population of giraffes with a variable neck size is taken into account. Those with a longer neck can reach higher tree branches, and thus have access to more food. This gives them more energy and an advantage in reproduction, which in the long run will lead to the production of more offspring. If we assume the genetic basis of the length of the neck, then, most likely, a longer-necked offspring will be born, which will displace the short-necked one for many generations.
In Lamarckism, the giraffe needs to reach taller trees, and therefore its neck lengthens, and this is transmitted to the offspring.
Now the fallacy of the second core of the theory that Jean-Baptiste Lamarck created is obvious.
Useful mutations are an exception, not a rule
The scientist's contribution - the idea of progress on a complexity scale - is also not confirmed even at the molecular level. Motu Kimura and Tomoko Ohta, founders of the currently prevailing neutral and near-neutral theories of molecular evolution, have shown that the vast majority of mutations are neutral - they have no effect on the adaptability of the body. The second theory claims that many of the neutral mutations will have an effect too small to be really noticeable. The remaining mutations are harmful, and only a small number of them are actually useful.
If there was a predefined line of movement towards excellence, then all mutations would be beneficial, but this is not supported by evidence.
Thus, not a single concept of Lamarck was confirmed.
Panacea for theology
The idea of “life fluids” did not spread, so Lamarckism and evolution were disputed until Darwin's work “The Origin of Species” conquered the world. Darwin showed the reality of evolution. Nevertheless, he failed to convince everyone of natural selection.
The idea of inherited acquired characters, which even Darwin used, became synonymous with Lamarckism, as well as a number of theories that arose in opposition to natural selection. In scientific circles, neolamarism then generally defeated Darwin's theory. Theology, which half a century ago was ardently opposed to Lamarckism, now fully accepts it only because the action of the “vital fluid” can be easily attributed to a creative deity who intelligently designs adaptation to the environment, which turned out to be more convenient than the “accident” of natural selection.
In 1900, Neolamarckism and selectionism were crushed by the rediscovery of genetics and the emergence of mutational theory.
Militant Lamarckism Lysenko
One of the black chapters in the history of biology and science as a whole has unfolded in Russia: Lysenkoism. Trofim Lysenko was a mediocre scientist with tremendous political influence, which he used to rise to the top of Soviet biological science, and by the 1930s he became head of the Academy of Agricultural Sciences. Here, he imposed dictatorial methods on his own idea of evolution - the “Michurin method”, a type of Neolamarism, and persecuted geneticists who disagreed with this position. Michurinism became the “new biology” that was well suited for collectivization, as it mixed politics with pseudoscience. Lysenkoism was officially ended in 1964.
Is Epigenetics a New Lamarckism?
Thus, with a theory alternative to natural selection, the question was closed. However, in 2013, Jean-Baptiste Lamarck, whose contribution to biology - Lamarckism - turned out to be untenable, got a chance for rehabilitation. Then a work was published, according to which mice trained to fear the smell of acetophenone transferred this ability by inheritance. New Scientist magazine called the work a confirmation of the inheritance of the acquired Lamarck traits. True, the effect is based on epigenetics - a change in the work of genes, and not of the genes themselves, which does not contradict natural selection. Thus, the evolutionary teachings of Jean-Baptiste Lamarck can be rehabilitated again.