The rich set of interactions between individuals in society^,,,,,, results in complex community structure, capturing highly connected circles of friends, families or professional cliques in a social network^,,,,. Thanks to frequent changes in the activity and communication patterns of individuals, the associated social and communication network is subject to constant evolution^,,,,,,. Our knowledge of the mechanisms governing the underlying community dynamics is limited, but is essential for a deeper understanding of the development and self-optimization of society as a whole^,,,,,. We have developed an algorithm based on clique percolation^, that allows us to investigate the time dependence of overlapping communities on a large scale, and thus uncover basic relationships characterizing community evolution. Our focus is on networks capturing the collaboration between scientists and the calls between mobile phone users …