Who was a famous anthropologist who believed that to truly learn about another' s culture and their customs you needed to live among the people?

This was Bronislaw Malinowski.

He was a famous Polish anthropologist, who later was based in London. He himself studied Melanesian cultures, such as on Trobriand Islands. Much more than for his work, however, he is known for his contribution to the methodology of anthropology: instead, like his colleagues and predecessors, studying foreign cultures from books, he insisted on gaining a personal experience.