The evidence of common ancestry is based on study of three parameters; fossils record, homologies of various organisms, and study of biogeography. Fossils record determines the similarity and differences of bones as well as shells of different organisms over a given period of time. On the other hand, studying of homologies involves assessment of mitochondrial DNA and other proteins with an aim of finding similarity from one organism to another. Finally, Biogeography is the assessment of how continental drift might have separated organisms which had got common ancestry and they were living together.