Final answer:
Franz Boas championed the approach of historical particularism, which claims that each culture evolves uniquely based on its history and interactions, rather than following a single linear path.
Step-by-step explanation:
Franz Boas, a pivotal figure in the field of anthropology, fervently opposed the concept of unilineal cultural evolution, which suggested that all cultures progress through the same set of stages towards what was then considered "civilization." Instead, he put forth the idea of historical particularism, a perspective that argues each culture evolves in its own unique way, shaped by its specific historical circumstances and interactions with other cultures. Boas emphasized the importance of considering each culture's distinct path, rather than forcing a linear evolution model upon disparate cultural contexts. His approach marked a significant departure from the then-prevailing ethnocentric views in anthropology and laid the groundwork for modern cultural relativism.