Jean-Baptiste Lamarck
Jean-Baptiste Lamarck, a French naturalist was an early proponent of the idea of evolution. His full name was Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck. However for the sake of simplicity people addressed this scientist as Jean-Baptiste Lamarck or simply Lamarck. His theory of evolution is popularly known as Lamarckism. He was also one of the first to use the term biology in its modern sense and coined the term invertebrates.
Lamarck was born on 1 August 1744 at Bazentin-le-Petit, Picardie in France into a poverty-stricken family – the title Chevalier was used to depict the occupation his flock. He was the youngest of eleven children in a family with a centuries-old tradition of military service; his father and a number of his brothers were soldiers. He joined the army to serve his country as an army man prior to getting involved in natural history and writing about flora of France in three volumes with the title Flore française. This made Lamarck more popular and helped him get an appointment in National Museum (Muséum national d'histoire naturelle) in Paris. After years of working on plants, Lamarck was appointed curator of invertebrates in the museum and got the chance for a series of public lectures subsequently.
Before 1800, like may others, Lamarck was also an essentialist with the thought that species were unchanging. However, after his works on the mollusks of the Paris Basin, he came to a the conclusion that change in the nature of species did occur over time. He gradually developed an explanation and outlined the same in his work, Philosophie Zoologique in the year 1809.
The theory of evolution put forward Lamarck is popularly known as Lamarckism or Lamarckian evolution theory, based on the heritability of acquired characteristics. This theory was once a widely accepted idea - that a living organism can pass on characteristics acquired during its lifetime to its progeny.
Lamarck had a strong belief that individual efforts of the organisms during their lifetime were the main driving force of the species to better adaptation in respective environments. In turn they would acquire adaptive changes and pass them on to the next progeny. Lamarck’s theory was was highly popular during the early nineteenth century as an explanation for the complex nature of the living world. However publication of Darwin's theory of natural selection, the importance of Lamarck’s theory emphasizing individual efforts towards adaptation considerably got reduced.
The evolution of giraffe necks is often used as the example in explanations of Lamarckism. He proposed in his book Philosophie Zoologique of 1809 the theory that characteristics that were needed were acquired/diminished during the lifetime of an organism were subsequently passed on to the next generation. He observed this phenomena in the development of species in a progressive chain of development, towards higher forms of living organisms.
Lamarck’s theory was based on two premises, considered to be generally true during his time:
Organisms lose characteristics they do not use/require, and develop characteristics that are useful.
Organisms inherit the traits of their ancestors.
On the basis of these premises Lamarck developed two laws:
Law of use and disuse. In every animal that has not reached the limit of its development, a more frequent and continuous use of any organ gradually develops that organ, and gives it power. Whereas the permanent disuse of any organ irreversibly weakens and deteriorates it, and diminishes its functional capacity in a progressive manner until it finally disappears.
Inheritance of acquired traits. All the improvements or losses caused by an individual or by nature are preserved and transmitted by reproduction to the new individuals This is subject to the condition that the acquired modifications are common to both the sexes, or at least to the parents which produce the young.
The most common examples of Lamarckism are:
Giraffes' stretching of their necks to reach foliage high in trees, gradually enhancing the strength and length of their necks. These giraffes give birth of offspring with slightly longer necks.
A carpenter, by way of his work, strengthens the muscles in his arms. His sons will also have similar muscular development when they mature.
In fact, a change in the
environmental parameters bring about change in ‘needs’ of an
organism. This results in change in behavior, change in organ usage
and development, change in form of the individual over span of
time—resulting in gradual transmutation of the species.
Lamarck’s theory might explain the observable diversity of species implying the first law generally as true. The main argument against Lamarckism is that experiments do not support the second law. The ‘acquired traits’ bear no tangible sense in the matter of inheritance. Lamarckism gained initial acceptance because the people were not aware of the mechanism of heredity before publication of the Laws of Heredity by Gregor Johann Mendel.
Lamarckism and Unicellular Organisms
There is no evidence that acquired changes are genetically transmitted, particularly in case of higher organisms, but some scientists are of the opinion that the inheritance of induced changes among bacteria and protozoans are very common phenomena.
John Cairns, Julie Overbaugh, and Stefan Miller in their published work in Nature in 1988 have pointed out that some E. coli mutations could develop in a Lamarckian manner, thus supporting the Law of Inheritance of Acquired Traits.
In spite of major limitations in Lamarck’s second law, in the light of present advancement enough evidence is found that cells can activate low-fidelity DNA polymerases in stressful conditions to induce mutations. While the acquisition of new genetic traits is random, and selection remaining Darwinian concept, the active process of identifying the necessity to mutate by micro organism is considered to support Lamarckian approach.
Many historians opposed to linking Lamarck's name to the theory that bears his name. According to them, Lamarck deserves credit for being an early proponent of the concept of biological evolution. But by no means he can be treated as a scientist who explained the mechanism of evolution. Rather, he simply followed the accepted propositions of his time. Lamarck’s belief in organic evolution was not at all acceptable to such historians because at his time there was no theoretical framework to explain the concept of emulation.
Lamarck died 30 years before the publication of Charles Darwin's book ‘Origin of Species’. Stephen Gould as science historian, evolutionist, and paleontologist in this regard noted that if Lamarck had been aware of what Darwin did proposed as mechanism of natural selection, there was no room for doubt that Lamarck would not have accepted it as a more logical proposition to the laws proposed by him. Nonetheless, an important point in Lamarck's favour at the time was that his theory contained a mechanism to explain how variation is maintained, that was lacking in Darwin’s own theory.
Moreover, while Darwin proposed natural selection as the main mechanism for development of species, in the text ‘Origin of Species’, but he did opposed the idea of a variant of Lamarckism as a supplementary mechanism in the process of evolution.
However Lamarck's important theory, the inheritance of acquired characteristics was widely rejected. The renowned evolutionist August Weismann disproved the theory by cutting the tails off mice, demonstrating that the character of the amputated tail was not passed on to the offspring of those mice. However, we may argue that Lamarck never counted injury or artificial deformation as a true acquired characteristic. To be more specific, only those traits, which were initiated by the animal's own needs were deemed to be passed on to the next progeny.
Lamarck's works however never became popular during his lifetime and he did never earn the respect or status enjoyed by his patron Buffon or his colleague Cuvier. Though Cuvier respected Lamarck's work on invertebrates, he did not consider Lamarck's theory of evolution to be of any use. Rather, Cuvier used his personal influence to demean Lamarckism.
During his carrier Lamarck published a series of books on invertebrate zoology and paleontology. Of those, Philosophie Zoologique, published in 1809 explicitly contained Lamarck's theories of evolution. The first volume of Histoire naturelle des Animaux sans vertèbres was published in 1815, and its second volume in 1822. In addition to Lamarck's contributions to evolutionary theory, his works on invertebrates represent a significant advancement over existing classifications of animals. He was the first biologist to differentiate Crustacea, Arachnida, and Annelida from the class Insecta. Besides, his classification of the mollusks was much more advanced of anything proposed earlier by others. Lamarck had foreseen the work of Schleiden and Schwann over biology of cells in as much as stating that, “No body can have life if its constituent parts are not cellular tissue or are not formed by cellular tissue.”
Interestingly, Lamarck even developed the
capability and found time, to write papers on physics, meteorology,
including compilations of some annual weather data.
Later Life
Lamarck's life was the tale of a constant struggle against poverty. The matter became worse when he began to lose his sight around 1818 and passed his last years completely blind in penniless condition, cared for only by his poverty stricken beloved daughters. When he breathed his last on 28 December 1829 in Paris, he received a poor man's funeral, excepting the homage paid by Geoffroy Saint-Hilaire, one of his colleagues. Jean-Baptiste Lamarck, who became the symbol of struggle, was buried just in a rented grave. After five years his body was removed from that grave - and no one now has any idea as to where his remains are!
Author’s Note
For this Article I have collected information from some important sites through internet and also from some college level texts. I have tried to put such information in simple and laconic form, understandable to the readers who are even outside the field of biological science.
Though Lamarckism is considered an obsolete concept by many experts, I have the strong conviction that it is very much relevant even today and will continue to be so in future as well.
Jean-Baptiste Lamarck was a highly talented biologist with enough inter-disciplinary knowledge. But he did not get fair treatment during his life or at the time following his death. This happened in a country like France, considered a society of cultured people!
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