Lamarck’s Theory of Evolution, also called Lamarckism, was proposed by Jean-Baptiste de Monet Lamarck in the year 1744-1829. Lamarckism is related to the inheritance of acquired characteristics. In Lamarck’s theory of evolution, the environment plays a crucial role in driving evolutionary changes. In this article, we will study Lamarck’s Theory of Evolution, its postulates, and examples.

What is Evolution?

Evolution is the gradual process by which simpler species of animals and plants change over many generations to form more complex beings. Evolution is a slow process that occur due to changes in the gene pool. Evolutionary changes in organisms are stimulated by environmental factors, predators, etc.

There are mainly four types of Evolution:

• Divergent Evolution
• Convergent Evolution
• Parallel Evolution
• Coevolution

Types of Evolutionary Theories

Among various theories of evolution, the most important ones are:

• Theory of Lamarck or Lamarckism: The traits acquired by any generation will be inherited by the next generation of the same species. Acquiring new traits completely depends upon the species.
• Theory of Darwin or Darwinism: In nature only those species which are capable to adapt with the changing environment will survive on the earth while others disappear.
• Theory of Mutation: Proposed by Hugo de Vries, this theory suggests that a sudden change in the DNA due to mutation creates new species in the world.
• Synthesis Theory or Neo Darwinism or Modern Theory: Most accepted theory by scientists, it is a combination of all the above three theories.

Lamarck Theory of Evolution

This theory of Lamarck is popularly known as the “Theory of Inheritance of Acquired Characters”. It suggests that if a specie acquired new traits, they will be inherited by the next generation too. In this way, a completely new specie will be developed. Lamarck’s Theory of Evolution is based on adaptive modifications. This theory of Lamarck has some supportive examples but is also criticized by other scientists as well.

Postulates of Lamarckism

Lamarck’s theory of evolution is mainly based on four basic postulates –

New Organs are the Result of Need

Formation of new body parts is a result of a new need (or want) which has arisen and continues to be felt by the organism. This need may arise due to changing environment or to escape predators.

Organisms Driven to Greater Complexity

According to Lamarck, organisms adapt to their environment. This leads to change from their simple towards more complex form.

Also Read: What is Adaptation?

Inheritance of Acquired Changes

Lamarck postulated that the characters which are developed by an individual during its lifetime would be inherited by their offspring as well. To support this point he gave an example of a blacksmith who develops strong arms due to his rigorous work. This is why his children would inherit strong arms too.

Use and Disuse

The organs strengthens with more use and deteriorates with infrequent use. This use and disuse decide the strength, form, and functioning of organs.

Importance of Lamarckism

Scientists believe that Lamarckism is the very first evolutionary theory. It formed the foundation of evolutionary models. Basically, Darwinism is based upon Lamarckism. There are many supportive examples for Lamarckism but very few criticisms. This theory helps to solve maximum problems which are related to evolutionary changes. As this theory is simpler than Darwinism, this theory is also accepted by many scientists.

Examples of Lamarckism

Evolution of Giraffe

Lamarck state that the evolution of the giraffe is an example which supports his theory. According to Lamarck, the ancestors of giraffes were similar in figure to the present day deer with small neck and limbs. With time the surface vegetation was wiped off due to excessive feeding upon which led to scarcity of food. In order to adapt to this environmental change, giraffes stretched their neck to feed on the leaves of taller trees. This led to the development of long necks of giraffe which was inherited by successive generation.

Evolution of Ducks

The evolution of Ducks is another example of Lamarckism. According to Lamarck, the ancestors of ducks were not aquatic and lived inland. But due to lack of food and competition, they moved to the water. To adapt to this change ducks developed webs between their toes for wadding. Their wings became redundant with continuous disuse.

Evolution of Snakes

According to Lamarck, snakes once resided on the land & had limbs. Due to creeping mode of movement and burrowing habits, their limbs became useless and ultimately shed off. This is an example of use and disuse of organ.

Evolution of Humans

According to Lamarck, the human evolution of the appendix is another example. In ancestor human, the appendix was more developed & usable as they fed on green leaves. Appendix was useful in digesting cellulose. But as humans started cooking their food, the use of appendix reduced. In this way, the current human appendix is a vestigial structure in the human body.

Evolution of Flightless Birds

Birds like Ostriches were once capable of taking long flights. But due to some changes in the environment, they had a lot of food available easily and were well-protected. This change led them to stop using their wings resulting in formation of vestogial wings.

Criticisms of Lamarckism

Experiments with Rats

Scientist August Weismann experimented with rats & disproof the theory of Lamarckism. He experimented with a bunch of rats and cut down their tails and left them to reproduce. Again in the next generation, he cut down the tails of rats and left them to reproduce. In this way, he repeated his experiments on 20 generations of rats. But no rat was born without a tail or reduced tail size. In this way, Weismann disproved the theory.

Experiments with Drosophila Flies

Scientist Cuvier experimented with Drosophila flies. He kept them in the darkroom and left them to breed. He repeated the experiment till the 75th generation of the files. But no generation was born blind. Hence, he proved that flies did not adapt to the change in environment and eyes did not become useless.

Lamarckism and Neo Lamarckism

Lamarckism suggests that organisms can pass on characteristics acquired during their lifetime to their offspring. This theory, although widely discredited in modern biology, laid the foundation for evolutionary thought.

Neo-Lamarckism was a revival of Lamarckian ideas. It emerged in the late 19th and early 20th centuries. Neo-Lamarckists proposed that acquired traits could be inherited through non-genetic mechanisms such as Lamarckian inheritance. However, contemporary scientific understanding emphasizes the role of genetic inheritance in evolution

Lamarckism v/s Darwinism

The difference between Lamarckism and Darwinism is given below: