Etymologists have charted the evolution of languages much like ancestral family trees. The profliferation of languages is because of our migration across the globe. Communities formed, but had little to do with groups farther than a day's walk away. In isolation like this, language diverged. Later, as groups encountered and merged with other groups, the languages they carried with them merged and evolved into something new.

I read something interesting a few years ago. It speculated that all languages were mingling and merging, heavily influenced by English, which is itself a kind of conglomerate language. The article projected that a new universal standard language was evolving from current English. The writer thought that the final standard form would be as different from English as we know it as is the "English" of the original Beowulf.