We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
It is now widely believed that essentially all 6000 world languages evolved, by geographical separation, from one proto-language. (This theory tends to undermine Chomsky's claim to fame for theorizing an internal hard-wired grammar - Chomsky's sole interesting idea, in my opinion.)
However, languages are dropping like flies, as the planet shrinks. McWhorter in the NYSun argues that this is a good thing, but he hopes hobbyists will keep the old ways alive.
Will the universal language be English? I hope so. It's a pretty good language, but Italian is far more musical, and I'd be happy to have an excuse to learn it. Would no longer need a translated libretto for the operas I love.
Since writing was developed thousands of years after language existed, the only hard evidence we have is physiological (speech centers in the brain, the hyoid bone, and the postition of the larynx). The problem with this physiological evidence is that it's indirect: the presence of all these features tells us that human beings had the physical ability to have language, but it tells us nothing about when or how language developed. Those are things we can never know. But barring other evidence, the only honest position is that human beings developed language just after they had the ability to do so ("honest" meaning based on evidence), so yes, we must assume that if there was an initial community with the ability to speak, all languages ultimately developed from one (though there are alternate theories that do not assume one initial community). Chomsky's UG is sufficiently abstract and general that it applies to all languages (the word "grammar" doesn't mean what you think in that term).
If Noam (can't say his last name because I want to bite) is correct - that we are hardwired for grammar, then we have a lot of dumb people in the world. Might as well say we are hardwired for algebra. Language operates through the lateral association of metaphor rather than some vertical nameing identification. Every word was a metaphor first. Except for 'the'. Maybe 'the' was, come to associate with it. One had to have pointed first.
Robert Heinlein said: Language itself shapes a man's basic ideas. I have to go with that. The use of the word 'like' five times in one utterance is enough to convince anyone the speaker lacks ideas.
Ahh, grammar - the stuff of teacher-lounge complaining. "I can't BELIEVE I have to teach grammar when my twelfth-grade syllabus has no space for it! Oh, woe is me! Why can't the kids just learn it in the fifth-grade like they're supposed to. Must be stupid teachers, don't you know. (College professors think high school teachers are useless idiots. High school teachers think college professors are from another planet.)
y'know, I mean like y'know--why is it that our children have acquired these bizarre speech patterns during the last 35 years? Do you suppose it has something to do with discipline both at home and in the classroom? Maybe teachers are so absorbed with so many other issues that they don't have the time for the constant, re-affirming, never-ceasing, relentless guidance and correction necessary to truly educate in the tough subjects! But, like wow, y'know that would be reallly boring y'know.