Overlapping generations

In population genetics overlapping generations refers to mating systems where more than one breeding generation is present at any one time. In systems where this is not the case there are non-overlapping generations (or discrete generations) in which every breeding generation lasts just one breeding season. If the adults reproduce over multiple breeding seasons the species is considered to have overlapping generations. Examples of species which have overlapping generations are many mammals, including humans, and many invertebrates in seasonal environments.^{[1][self-published source?]} Examples of species which consist of non-overlapping generations are annual plants and several insect species.

Non-overlapping generations is one of the characteristics that needs to be met in the Hardy–Weinberg model for evolution to occur. This is a very restrictive and unrealistic assumption, but one that is difficult to dispose of.^{[2][self-published source?]}