polygenesis

noun

1. (uncountable, usually)The genesis of a species from more than one ancestor.

   “After polygenesis was soundly rejected by theologians, it was taken up with enthusiasm by many scientists. Thomas Henry Huxley published Evidence as to Man's Place in Nature in 1863, applying Darwin's evolutionary theory to human origins. […] Evolutionary polygenesis, of course, did away with belief in Adam and Eve, and instead asserted that humans arose as a population.”

2. (uncountable, usually)The theory that living organisms originate in cells or embryos of different kinds, instead of coming from a single cell; as opposed to monogenesis.
3. (uncountable, usually)The theory that languages developed independently in different places at different periods, as opposed to originating from a single source.

   “The alternative to monogenesis for the origin of language is polygenesis, i.e. that language originated in human evolution at a number of distinct points. If polygenesis is assumed, then the different protolanguages would have developed independently and lead over millennia to the diversity of the descendant languages found at the present day.”

4. (uncountable, usually)The emergence from multiple causes or origins.

   “The contrasting theory of polygenesis assumes that resemblances among tales can be attributed to independent invention in places unconnected by trade routes or travel.”