"Historical linguistics as we know it began in the late eighteenth century, when Western European scholars began to notice some linguistic characteristics that were shared among ancient European and Asian languages, such as Latin, Greek, Gothic, Older Persian, and Sanskrit. These similarities led linguists to believe that these languages, and their modern descendants, must have evolved from a single ancestor language called Proto-Indo-European (PIE). "
Vedrana Mihalicek and Christina Wilson (Eds.) 2011. Language Files: Materials for an Introduction to Language and Linguistics. Columbus: The Ohio State University Press, 523.