Summary This paper compares the romanization of Gaul in the 1st century BC and the gallicization of the island of Martinique during 17th-century French colonial expansion, using criteria set out by Muf- wene's Founder Principle. The Founder Principle determines key ecological factors in the formation of creole vernaculars, such as the founding populations and their proportion to the whole, language varieties spoken, and the nature and evolution of the interactions of the founding populations (also referred to as “colonization styles”). Based on the comparison, it will be claimed that new languages arise when a language undergoes vehicularization and subsequently shifts from one speech community to another. In other words, linguistic genesis would be a complicated case of language contact, where not only one, but sev- eral dialects of both superstrate and substrate varieties are involved, in a historical context where the identity function of language, or the norm, is overriden by the need to communicate. Research also indicates that language varieties spoken at the time of the shift did not pertain to normative usage, but to popular varieties, dialects, or both, since the emerging vernaculars - in Gaul, as well as in Martinique - preserved some of their phonological and lexical particularities.