Heredity and variability (“descent with modification” per Charles Darwin) are the two basic phenomena behind speciation. Chromosomes, as carriers of genetic material, provide the precise inheritance of DNA. Through homologous recombination, genetic diversity increases. In the event of a deleterious mutation, a gametogenesis fail occurs, mainly in meiosis through the checkpoint systems that eliminate defective cells during certain meiotic stages. This distinctive feature of speciation, in which divergence is ensured by chromosome mutations (changes in the structure and/or number of chromosomes), establishes postzygotic reproductive isolation due to the sterility or decreased fertility of hybrids.