Final answer:
Franz Boas disagreed with E.B. Tylor and Lewis H. Morgan's unilineal cultural evolution theory, emphasizing individual cultural trajectories and intercultural influences in his anthropological work. He advocated for field research and a holistic approach to anthropology, strongly opposing ethnocentric and racist ideas prevalent in his time.
Step-by-step explanation:
Franz Boas famously disagreed with the theories of cultural development proposed by E.B. Tylor and Lewis H. Morgan, who believed in unilineal evolution of cultures. Instead, Boas suggested that each culture develops through its own unique historical trajectory and that cultures are influenced by each other through trade, migration, and conquest. His ethnographic data challenged the prevailing ethnocentric and racist theories, particularly those that supported the concept of White supremacy.
Boas is also known for his significant contributions to the field of anthropology, insisting on the importance of obtaining ethnographical information directly from the peoples being studied and advocating for a holistic approach to anthropology. His work had a substantial impact on the study of culture and played a role in the development of modern anthropological methods. He emphasized the diffusion of ideas among cultures and debunked biological determinism, as demonstrated by his studies on the changes in skull sizes of American immigrants, highlighting the influence of environmental factors on physical characteristics.