Groups that were viewed as a culturally distinct multi band population that imagined itself as one people descended from a common ancestor, and are currently described as an indigenous group with its own set of loyalties and informal leadership living to some extent outside the control of a centralized authoritative state are known as:.

Tribe

Explanation:

Tribe is a type  of human social group used in anthropology. The definition of tribe is as mentioned in the question.

Tribes are a political group molded from an organisation of families (which are clans and lineages) who posses social and ideological solidarity. Membership of a tribe is based on factors like kinship ("clan"), ethnicity ("race"), language, living place, political group, religious thoughts,  tradition and cultural practices.