Final answer:
Tylor and Morgan believed in unilineal evolution, while Boas emphasized the uniqueness and interaction of cultures.
Step-by-step explanation:
Both Tylor and Morgan, like most anthropologists of their day, believed in the theory of unilineal evolution, which stated that all cultures followed a single set of stages towards civilization. However, Franz Boas disagreed with this idea and argued that each culture evolves uniquely according to its own historical trajectory and that cultures are constantly changing through interaction with each other. Boas emphasized the diffusion of material objects, practices, and ideas among cultures through trade, migration, and conquest.