Evolution is a theory. Theory has been tested and subjected to verification through accumulated evidence. The theory of biological evolution has been supported by a mounting body of fossils, anatomical, embryological, biochemical, biogeographical and genetic evidences. There are also many scientists with fascinating ideas that explain how the universe, our galaxy, primitive earth, biological macromolecules and life originated, but there is very little that we know for sure. However, current understanding on the area shows that the evolutionary unit is a population and the change in gene frequencies of population over time traces evolution. The forces that drive change in gene frequencies in population includes:natural selection, mutation, migration and genetic drift. These evolutionary forces through time causes reproductive isolation, and result evolution of new species.