The definition of ethnicity that people in political science tend to use focuses on perceived common ancestry centering around a few markers of identity. The definition in my dissertation and first book:
"Ethnic groups are 'collective groups whose membership is largely determined by real or putative ancestral inherited ties, and who perceive these ties as systematically affecting their place and fate in the political and socioeconomic structures of their state and society (Rothschild 1981).' These ties usually are related to race, kinship (tribe or clan), religion and language."In the intervening years, not much has changed. In a forthcoming piece of which I am one of many co-authors, the focus is very much on defining what counts and what does not count for the dataset:
Consequently, the AMAR criteria that aim to outline socially relevant groups at a given point in time are that:Why is religion part of ethnic identity when we see so often people refer to "ethnic and religious" or "ethnoreligious"? Because it is about identity and one that is seen as inherited. Sure, people can convert to a different religion, but other "markers" of identity are also more malleable than advertised. Languages can be learned and adopted. One can move to a different region and then identify with that region (I am reminded of the "Californian since 1970 or 1980 bumper stickers"). One could argue that race is fixed, but yet not so much as people of mixed race can try to identify in a variety of ways. Kinship often means multiple identities as well.
(1) Membership in the group is determined primarily by descent by both members and non-members.
(2) Membership in the group is recognized and viewed as important by members and/or nonmembers. The importance may be psychological, normative, and/or strategic.
(3) Members share some distinguishing cultural features, such as common language, religion, occupational niche, and customs.
(4) One or more of these cultural features are either practiced by a majority of the group or preserved and studied by a set of members who are broadly respected by the wider membership for so doing.
(5) The group has at least 100,000 members or constitutes 1% of a country’s population.
Folks who study ethnicity are very aware that it is a socially constructed thing, so the boundaries are fuzzy and one's identity is not entirely up to oneself but how other see it. Note number 2 of the AMAR criteria--that the membership is defined by members and nonmembers--not by oneself.
For me, in my research, religion does much of the same causal work as language or race or kinship--creating a sense of affinity or enmity which then affects policy preferences--do we want to help group x or group y? Let's help the group with whom we share some ties--racial, religious, regional, kinship, or linguistic. When identities cross-cut, then politics is about defining which ties are the most salient. When identities converge--group x shares the same religion, language and race as group y--the politics became easier. It becomes less about defining which identity matters and more about defining oneself as the best defender of the group.
Which leads us to ethnic outbidding. When politicians compete to be the best defender of group x, each one may try to top the other, as in an auction for support from the group. The claims become more and more radical. Religious outbidding and linguistic outbidding are not that different--just the promises will vary.
For my work, the key difference between religion and other ethnic identities is really about the reach. That religious identities cross not just land borders but across oceans so that Libya supported the Moros of the Philippines, for instance. Race can have the same distance, but clan/tribe and language much less.
Each kind of ethnic tie will have different implications for politics, as I discussed early in my blogging career. Religious differences have implications for much of what governments do, whereas linguistic divides matter for employment and education more so than elsewhere. Race? The irony here is that race does not really have much in the way of logical implications for politics until/unless racial divisions have historical content. And yes, then it matters quite a bit.
Anyhow, a long answer to a simple question. When we speak of ethnic groups, ethnic ties, ethnicity in poli sci, the concept includes religion as a potentially relevant component. Why? Because it is how people identify us and them in social groups that sometimes become politically relevant.