I have always wondered how modern French, a Latin-derived language, came to be the predominant tongue spoken among the modern people who inhabit the region we know as "France." I know that during the fall of the Roman Republic, Gaul (modern France) was inhabited by Celtic language speakers, and that at during the fall of the Empire, it was primarily occupied by German language speakers (Franks). I assume that during the period of the German invasions, Gallo-Roman elites who spoke Latin ruled over a primarily Celtic speaking population, and that as the invasions continued, the population became predominately German speaking. In short, how did this Celtic and German speaking population come to adopt a Romance language? Additionally, why did this same process not occur in Britain or the Holy Roman Empire?
The short answer is: because not nearly enough Germanic speakers made the trek across the Rhine to significantly affect the makeup of the people who lived there. This holds true in Visigothic Spain, Vandal Africa, and Ostrogothic/Lombard Italy as well. The Germanic immigrants in all of these successor kingdoms formed a small but privileged warrior aristocracy that, over a number of generations, was increasingly, but not wholly, subsumed by the broader culture, adopting its language, faith (the Franks and Goths were mostly Aryan Christian originally, only later converting to Catholicism), and some of its traditions. It's important to remember that most of the Germanic groups that came into the empire in its last days, especially the Franks and Goths, had been in extensive contact with Rome for hundreds of years, and looked upon the empire far less as either victim or villain, but as something worthy of respect and emulation. The Roman senate, for instance, continued to function for decades after the Ostrogothic takeover, and both in Italy and in Spain the preexisting Roman bureaucracy was retained as long as educated Romans could be found to run it.
Historians aren't exactly sure why this didn't happen in England. The older theory is that the Germanic invaders slaughtered and/or drove out the native Romano-Celtic population and settled the land with their kin, but this has been generally rejected; for one thing, genetic testing of modern English people (source: Jennifer Paxton) has revealed no such ethnic purity, but rather the expected mixing of native and immigrant. If forced to hazard a guess, I would say that the reason England retained a more Germanic culture, or at least language, might be a combination of A) Britannia being less fully Romanized than the continental provinces; B) the migrant peoples (Angles, Saxons, Jutes) having far less contact with, and reverence for, Rome; and C) the peculiar political situation that developed, whereby for several hundred years the disunited Germanic kingdoms located in the south and east were almost perpetually at war with the Brythonic kingdoms of the north and west.
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