Definition of polygenesis:
(n) :
(biology) The theory that living organisms originate in cells or embryos of different kinds, instead of coming from a single cell; as opposed to monogenesis.
(n) :
The genesis of a species from more than one ancestor.
(n) :
(linguistics) The theory that languages developed independently in different places at different periods, as opposed to originating from a single source.
(n) :
The emergence from multiple causes or origins.