Theories of evolution/mechanism of evolution

Lamarck’ theory of evolution/Lamarckism: based on acquired characters through use and disuse.


This theory was put forward by a French biologist Jean baptiste Larmarck in 1809. his theory resolves itself into 3 factors namely;

a)      influence of the environment

b)      Use and disuse

c)       Inheritance of acquired characters



Based on the above factors, he suggested that; when an organism develops a need for a particular structure in a given environment, this will induce its appearance and there fore the structure will develop to carry out the need in that environment. This idea was based on the observation that the structures which are subjected to constant use become well developed and those which are not used tend to degenerate hence the theory of Use and disuse

For example;

i) Ancient giraffes were those living today. Lamarck urged that as the number of giraffes increased, there was shortage of food in form of grass, herbs and leaves from very short shrubs. This compelled them to stretch their necks so as to reach for leaves on higher branches of tall trees. The result was elongation of the necks.

The off springs of these giraffes inherited the longer necks, stretched further and the process was repeated until the present long necks were developed.

ii) exercise and training can lead to the development of muscles of a heavy weight lifter, since he suggested that these beneficial traits acquired in an individual’s life can be passed onto the off springs, hence evolutionary change can be achieved via transmission of acquired characteristics, This implies that a heavy weight lifter who has acquired big arm muscles produces children with big arm muscles.

However this was proved totally wrong by genetic evidence that acquired characters can be inherited. This theory there fore is not scientifically accurate.