Final answer:
Franz Boas is best known for emphasizing the role of cultural relativism, rejecting theories of unilineal cultural evolution and promoting an understanding of cultures within their own unique contexts.
Step-by-step explanation:
Franz Boas emphasized the role of cultural relativism, challenging earlier anthropological theories of unilineal cultural evolution. He proposed that each culture develops through its own unique history and interactions with other cultures. Boas's approach fundamentally shaped the discipline of anthropology, drawing focus to the diverse forms of human cultural expression without placing them on a hierarchical scale toward civilization. Rather than accepting a predetermined path of cultural evolution, he recognized the importance of understanding cultures within their distinct contexts, thus laying the groundwork for what is known as historical particularism.