One of the important forms of non-kinship organizations in primitive societies is based on age- groupings.People belonging to the same age-group are classified together into distinct age-classes such as infants,children,adolescents,adults and old people.Persons of the same sex or of both belonging to the same age range are formally grouped together into distinctive age-sets.
Every age-set passes through a series of age-classes or stages.These successive stages of development in the life of an age-set constitute the age-grade.Thus the age-grades are the structural framework through which each age-set progresses.The age-sets are often named and have common and uniform symbols like dress,ornaments,emblems,badges etc.Each age-set has a distinctive status,characteristic forms of behaviour,specific occupations,ceremonial functions,recreation clubs etc.Members of an age-set are bound together by obligatory cooperation and mutual aid.
The formal recruitment into age-groups and the passing into higher age-grades involve collective ceremonial and ritual initiation.This is accompanied by special and specific instructions in tribal law,habits and customs.Physical initiation marks the attainment of maturity when the puberty rites for boys or girls are performed.Other public ceremonies such as extinguishing of fire and its ritual rekindling followed by dramatisation of birth and death,sacrifices are also performed.Payments of some kind contributing to public feasting may often be necessary at this juncture.The ordeal of initiation often involve seclusion as well as the imposition of food and other taboos.
The primary functions of age-groups lie in the maintenance of tribal way of life and the systematic transmission of tribal tradition from older to younger people.The lower sets are generally playmates and undergo informal training.The middle sets constitute youth receiving formal educational instructions perform public and sometimes military duties.The upper sets which comprise the older and senior most members of the tribe are usually vested with administrative powers and also ceremonial as well as ritual precedence.Further there are separate age-groups for females and males the corresponding set of girls and boys generally court and marry .
The bonds of age cut across those of clan,kinship and other personal affiliations by uniting persons of the same age group in an attempt to promote group solidarity and tribal integrity.Age group organizations are quite widespread among tribals in Africa like Nuer of Kenya,Masai of East Africa etc.In India tribes like the Oraon,Naga ,Munda and Ho reveal the presence and operation of age-group systems.