So why the difference between our species and others?
Well, here's a hint:
http://pubpages.unh.edu/~jel/Ldev.html
I'm too tired at the moment, and not professionally qualified anyway, to get into detailed explanation, but in essence: biology. We have bigger, better brains; to say nothing of mouth and vocal cord structure. The blog summarized in mav's link basically said in 12,000 words, allegedly, what we talked about here ages ago: essentially, that language developed out of need. The need for survival, that is. As in, "gurf" + [point] + [two-arm wave], then "oog" + [hand slashing across throat] = "Y'all head over thataway and run the critter toward me, and I'll kill it". Etc.

Here's an explanation by y'all's friend:
http://www.chomsky.info/articles/1978----.htm