English mathematician Godfrey II. Hardy and German physician Wilhelm Weinberg independently derived a mathematical model in 1908. This model explains what happens to the frequency of alleles in a population over time. Their combined ideas became known as the Hardy-Weinberg theorem. It states that If certain assumptions are met, evolution will not occur because the allelic frequencies will not change from generation to generation, even though the specific mixing•of alleles in individuals may vary. The assumptions oethe hardy-Weinberg theorem are as follows:
I. The population size must be large. Gene frequency does not change by chance in large population size.
- Mating within the population must be random. Every individual must have an equal chance to mate with any other Individual in the population. In non-random mating, some Individuals can more reproduce than others. Then natural selection may occur. Therefore. Mating should be random. Individuals cannot migrate into, or out of. the population Migration may introduce new genes into the gene pool. It can add or delete copies of existing genes.
4. Mutations must not occur. Or mutational equilibrium must exist. Some mutations take place from wild type allele to a mutant form. Some mutations occur from the mutant form back to the wild type. If both these mutations are balanced then mutational equilibrium is established. Thus no new genes are introduced in to the population from this source. These assumptions stop the change in allelic frequencies. Therefore, evolution does not occur. These assumptions are restrictive. A real population cannot meet these conditions. Therefore, evolution occurs in most populations. However, Hardy-Weinberg theorem provides a useful theoretical framework. The changes in gene frequencies in populations can be examined by this theorem.