The theory of evolution suggests that life on earth began as relatively simple and primitive forms, over a long period of time developing into various complex organisms due to environmental changes. Such developments involved in an evolution are very slow and gradual.

In 1809, a French biologist Lamarck proposed a hypothesis to account for the mechanism of evolution. He believed that evolution was a result of 'use and disuse'. He explained that with the long necks and legs of giraffes. He believed that the ancestors of giraffe were short-necked and short-legged. In order to obtain sufficient food from high trees, they needed to stretch their necks and legs.

Title: Evolution Timeline

Continuous stretching resulted in longer necks and legs and these acquired characteristics were passed on to the subsequent generation until the size of the present-day giraffe was reached. However, his hypothesis of the inheritance of acquired characteristics is incorrect because somatic acquired characteristics do not directly affect the germ cells and therefore cannot be passed on to the next generation.