...opportunity and social cohesion when power between groups is asymmetrically distributed, as in South Africa: While primary groups and networks undoubtedly provide opportunities to those who belong, they also reinforce pre-existing social stratification, prevent mobility of excluded groups, minorities...

...in-group/ out-group notions incorporated into this dichotomy/ but the concept of power is introduced: "While primary groups and networks undoubtedly provide opportunities to those who belong, they also reinforce pre-existing social stratification, prevent mobility of excluded groups, minorities...