The theory that living organisms originate in cells or embryos of different kinds, instead of coming from a single cell; -- opposed to monogenesis.

Origin from more than one ancestral line or stock; multiple origin of language families.

Polygenesis is a linguistic theory concerned with the origin of individual natural languages, holding that they come into being not by means of a linear progression from an ancestor language, but by input from one or more. Proponents of polygenesis hold that the concept of genetic relatedness between languages is inaccurate. This view of language genesis is not held by the majority of linguists, among whom the theory of monogenesis holds sway.