<P> Both ethnic affiliation ( e.g. Pathan , Sindhi , Baloch , Punjabi , etc . ) and membership of specific biraderis or zaat / quoms are additional integral components of social identity . Within the bounds of endogamy defined by the above parameters , close consanguineous unions are preferred due to a congruence of key features of group - and individual - level background factors as well as affinities . McKim Marriott claims a social stratification that is hierarchical , closed , endogamous and hereditary is widely prevalent , particularly in western parts of Pakistan . Frederik Barth in his review of this system of social stratification in Pakistan suggested that these are castes . </P>
who has said that caste is a closed class
Frederik Barth