Darwin’s theory of Natural Selection was accepted for a long time but later on, several objections were raised against this causo-mechanical explanation of the origin of new species. Some of the important objections are — 1. Darwin could not distinguish between heritable and non-heritable variations, also, he did not explain the origin of variation. 2.
Industrial melanism provides one of the best examples of evolution within species and of natural selection.
On his return to England in 1836 and for the next 17 years, Darwin worked diligently on the notes and specimens he had collected and made new observations. He was particularly interested in the obvious success of breeders in developing desired variations in plant and animal stocks. He wondered if this artificial selection of traits