When it comes to population evolution and genetics, we cannot fail to cite the Hardy-Weinberg principle which emphasizes that if evolutionary factors such as natural selection, mutation, migration and genetic oscillation do not act on a particular population, the frequencies genotypic proportions will remain constant.

The five requirements for a population to be in Hardy-Weinberg equilibrium are:

Large-scale breeding population: For a population to be in Hardy-Weinberg equilibrium, it is important that this population is large, as small populations favor genetic drift (unanticipated fluctuations in allele frequencies from one generation to another).
Random mating: In order for the Hardy-Weinberg equilibrium to occur, it is necessary that the mating occur at random, with no preference for certain groups within the population. In this case, we say that the population is in panmixia, that is, they all mate at random.
No mutations: Mutations alter the total alleles present in a population (gene pool). Therefore, in a Hardy-Weinberg equilibrium population, no mutations should occur.
No gene flow: When there is gene flow due to migration or immigration of individuals, some genes may be included or excluded from the population. Thus, in an equilibrium situation, no gene flow occurs.
Lack of natural selection: For a population to be in Hardy-Weinberg equilibrium, natural selection must not be acting on it. If natural selection acts, some genotypes will be selected, modifying the allelic frequencies of the population.