In pre-modern societies, status differentiation is widely varied. In some cases it can be quite rigid, such as with the Indian caste system. In other cases, status exists without class and/or informally, as is true with some Hunter-Gatherer societies such as the Khoisan, and some Indigenous Australian societies. In these cases, status is limited to specific personal relationships. For example, a Khoisan man is expected to take his wife's mother quite seriously (a non-joking relationship), although the mother-in-law has no special "status" over anyone except her son-in-law—and only then in specific contexts.