It refers to an approach on the renovating evolutionary theory, it is one that is responsible for unifying both the foundations on which natural selection is based and the most innovative discoveries regarding genetics. This theory was raised between the 1930s and 1940s by a group of scientists, who were based on genetic variation and natural selection, elements that come from the theories made by Darwin, but with a slight difference and that is that have certain changes thanks to the advances that today are had on ecology and genetics.

Neo-Darwinism established a series of bases in which it is ensured that the variability in the genes of a specific population occurs by simple chance thanks to the mutation, however today it has been shown that said change is the responsibility of certain defects in the DNA replication processes, in addition to this, it also established that these genetic changes are caused by the mixture of chromosomes produced during meiosis. This approach also affirms that evolution occurs mainly due to the variables that occur in the frequency of alleles, with the passage of generations, giving way to what is known as genetic drift, the flow of genes and later to natural selection.

For its part, with regard to speciation, it can occur progressively, when a set of individuals are isolated and cannot reproduce, due to different factors, such as geographical factors and even due to modifications within that population. The synthetic theory, as neo-Darwinism is also known, ensures that natural selection and progressive changes are the main element responsible for the evolutionary process, thus ruling out other theories such as orthogenesis, which ensures that elements external to the organic matter are those that lead to the evolution of species.

Some sectors that reject neo-Darwinism, argue that it does not conclusively demonstrate certain processes, such is the case of horizontal genetic information exchange between prokaryotic organisms, which has caused certain sectors to doubt certain theories raised by neo-Darwinism.