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Development of Evolution
Jean Baptiste de Lamarck, a French naturalist, first formulated the initial theory of evolution. Lamarck's theory of inheritance of acquired traits was later disproven following new discoveries in genetics.
Charles Darwin propounded a new theory in 1858 with his theory stating that all species evolved from common ancestors through natural selection. The theory was introduced in his book The Origin of Species published in 1859 and there, Darwin made use of three sources in the development of his theory. On his trip to the Galapagos Islands, he was also impressed by the wide variety of species on the South American Island. The synthetic theory combines natural selection and the principles of genetics and was introduced after much research was done on genetics. This filled the gap in Darwin's theory of natural selection.
The synthetic theory supports the fact that organisms are constantly responding to natural selection resulting in the accumulation of many small changes causing evolution. Biologists who advanced this idea pointed out that the fossil record shows little evidence of ancestral species gradually changing into new ones. A related idea is species selection which results from the differential rates of the occurrence of speciation and extinction among species.
Many people opposed Darwin's theory of natural selection (evolution) during his time and some states even banned its teaching in schools as it conflicted with some religious beliefs. Others simply thought that human beings were related to lower species and could not accept Darwin's theory. However, biologists felt that Darwin's theory contradicted the blood theory of heredity and therefore refused to endorse it.