Surely a Homo sapien with more advanced communication skills would have some kind of evolutionary advantage over his single-word grunting cousin.
For those of you who think both camps present pretty good arguments, there's good news: They aren't mutually exclusive. While science now shows us that it's likely there already were neural structures in place that allowed language to evolve, meaning it was likely exapted, that doesn't necessarily explain language in full, with all of its complexities. Stringing words together into sentences and the notion of grammar in language may have a lot to do with natural selection. So perhaps language was originally exapted, but was refined through Darwinian selection. Surely a Homo sapien with more advanced communication skills would have some kind of evolutionary advantage over his single-word grunting cousin. But that more refined Homo sapien wouldn't even have the opportunity to speak his first sentence if his brain hadn't evolved to allow him to make a primitive hammer.