ˌȯ(r)thə+ noun
Etymology: New Latin, from orth- + genesis
1. : variation of organisms in successive generations along some predestined line resulting in progressive evolutionary trends independent of natural selection or other external factors — called also determinate evolution ; compare orthoselection
2.
a. : the theory that social evolution takes place in the same direction and through the same stages in every culture despite differing external conditions
b. : variation of culture in a particular direction in accordance with internal predetermining factors rather than through external contact