Speed of linguistic change is not constant: it differs as between different language and dialects, and between different chronological periods. These differences are, at least to some extent, conditioned by social parameters. Two major social factors are involved in producing these different rates of linguistic change. There is, first, the role of the relative degree of contact versus isolation which speech communities have experienced: a good example is provided by the contrast between Faroese and Icelandic as opposed to the continental Scandinavian languages. There is, secondly, an important role for relative social stability versus social instability in the histories of communities. There is considerable evidence to suggest that conservative language varieties generally tend to be the ones which are relatively more geographically isolated than rapid-change varieties, as well as being relatively more stable as this paper illustrates, through a study of the linguistic consequences of social upheavals involving different historical periods, different continents, and different languages.