ABSTRACT
In modern terms, evolution is a phenomenon resulting from the interplay of evolutionary processes, such as natural selection and genetic drift, and evolutionary patterns, such as the constraints imposed by phylogenetic history and existing variations. Evolution implies genealogical links and, thus, evidence is sought in terms of shared traits across species. Molecular evidence has also been used to hypothesize the time elapsed since the divergence of different lineages. Such amazing discoveries open the possibility of combining paleontological and molecular evidence in a manner that would have been considered impossible just a few decades ago. It was artificial selection that inspired Darwin's insight on the role of natural selection in evolution. But sexual reproduction contributes to the preservation of genetic variability in additional ways. According to Darwin's theory of evolution by natural selection, the reproductive success of an organism is measured in terms of number of offspring it can contribute to the next generation, compared to the offspring produced by conspecifics.
