Language Evolution, Coalescent Processes, and

8robot communication systems in general. One particular question that 9 has attracted some interest has the following general form: how might a 10 group of linguistic agents arrive at a shared communication system purely 11 through local patterns of interaction and without any global agency enforc12 ing uniformity? In this paper, we consider a natural model of language 13 (or more precisely, word) evolution on a social network, prove several 14 theoretical properties, and establish connections to related phenomena in 15 biology, social sciences, and physics. 16