His analysis of "religion as a cultural system" was particularly influential outside of anthropology. David Schnieder's cultural analysis of American kinship has proven equally influential. Schneider demonstrated that the American folk-cultural emphasis on "blood connections" had an undue influence on anthropological kinship theories, and that kinship is not a biological characteristic but a cultural relationship established on very different terms in different societies. Prominent British symbolic anthropologists include Victor Turner and Mary Douglas. In the late 1980s and 1990s authors such as James Clifford pondered ethnographic authority, in particular how and why anthropological knowledge was possible and authoritative. They were reflecting trends in research and discourse initiated by feminists in the academy, although they excused themselves from commenting specifically on those pioneering critics. Nevertheless, key aspects of feminist theory and methods became "de rigueur" as part of the 'post-modern moment' in anthropology: Ethnographies became more interpretative and reflexive, explicitly addressing the author's methodology, cultural, gender and racial positioning, and their influence on his or her ethnographic analysis. This was part of a more general trend of postmodernism that was popular contemporaneously. Currently anthropologists pay attention to a wide variety of issues pertaining to the contemporary world, including globalization, medicine and biotechnology, indigenous rights, virtual communities, and the anthropology of industrialized societies. Modern cultural anthropology has its origins in, and developed in reaction to, 19th century ethnology, which involves the organized comparison of human societies. Scholars like E.B. Tylor and J.G. Frazer in England worked mostly with materials collected by others – usually missionaries, traders, explorers, or colonial officials – earning them the moniker of "arm-chair anthropologists". Participant observation is one of the principle research methods of cultural anthropology. It relies on the assumption that the best way to understand a group of people is to interact with them closely over a long period of time. The method originated in the field research of social anthropologists, especially Bronislaw Malinowski in Britain, the students of Franz Boas in the United States, and in the later urban research of the Chicago School of Sociology. Historically, the group of people being studied was a small, non-Western society. However, today it may be a specific corporation, a church group, a sports team, or a small town. There are no restrictions as to what the subject of participant observation can be, as long as the group of people is studied intimately by the observing anthropologist over a long period of time.