Final answer:
Unilineal Evolutionism, also known as the theory of unilinear cultural evolution (UCE), was a belief in the 19th century that all cultures pass through a single set of stages in the march towards civilization.
Step-by-step explanation:
Unilineal Evolutionism, also known as the theory of unilinear cultural evolution (UCE), was a belief in the 19th century that all cultures pass through a single set of stages in the march towards civilization. This theory argued that societies progress in a linear fashion, from the lowest level of savagery through barbarism to civilization. It incorporated the comparative method, psychic unity, parallel evolution, and progress to support the idea of cultural evolution. However, this view has been largely abandoned by anthropologists today as they now recognize that cultures change according to their own unique historical trajectories and in constant interaction with one another.