These differences would be increased by separation and the influence of the languages spoken by the native populations as they adopted the new language. The Belgae and the Celts in Gaul, described by Caesar, differed from the Iberians in Spain. Each of these peoples undoubtedly modified Latin in accordance with the grammars of their own languages, as normally happens when languages come into contact.
It is not difficult to understand the divergence of the Romance languages, and it is not the least interesting feature of the Romance group that we can observe here in historical time the formation of a number of distinct languages from a single parent speech. Such a process of progressive differentiation has brought about, over a greater area and a longer period of time, the differences among the languages of the whole Indo-European family