Why Are There So Many Human Languages?

Today as I walked with my dog, I overheard two people conversing... and I suddenly wondered "Why do we have so many languages?" We as humans have many different sounds to convey the same or similar ideas or experiences. Sharing a common language is often a kind of group identifier and creates boundary conditions via comprehension. There is even language within language-terminology, jargon, etc-that often signifies areas of interest or focus. Perhaps that's what language is at its core? An identifier of group or territory? Yet beneath all the different sounds or mediums to convey ideas, there still exists the common human experience of trying to live as best as we know how, trying to survive, grow, evolve, cope with the experience of living...