Reddit reviews The Symbolic Species: The Co-evolution of Language and the Brain

Correct.

When our ancestors developed stone tools, they became hunters not scavengers. The nutrient dense meat supported our larger brains and hunting created a "portable food niche" enabling them to leave the jungles and follow game out into the savannah and beyond.

Hunting in groups and still living in multi-male/multi-female groups defined humans as a species, encouraging monogamy, language development, and even controlling the evolution of our physiology (larger brains/smaller teeth).

Essentially MEAT IS WHAT MADE US HUMAN.

Terrence Deacon's The Symbolic Species: The Co-evolution of Language and the Brain is definitely a must. Great read, too!

EDIT: Notice that it's not about the development of language in evolution, but how language and evolution co-evolved. If you're into human vs animal communication, neuro-stuffs, even semiotics, this book will be for you. Oh, and yeah, he criticizes Pinker, Chomsky, et al. So if you already know about generativism, this will be a good gateway towards modern cognitive science and cognitive linguistics.

Last semester, I took an awesome intro to biological anthropology class and we read excerpts from the professor's book (so I have not yet read the entire book, though I plan to do so soon!) Maybe this is something you'll be interested in; hope this helps!
http://www.amazon.com/The-Symbolic-Species-Co-evolution-Language/dp/0393317544/ref=sr_1_1?ie=UTF8&qid=1343888665&sr=8-1&keywords=the+symbolic+species

Well, it's not my phrase. That's what the study of the origins of language is referred to as in Linguistic literature. It's actually somewhat confusing, because "the evolution of language" refers to how language originated both as a social structure and as a biological feature of humans, while "language evolution" refers to the processes by which established languages change over time (ie, Old English becoming Middle English becoming Modern English).

Also, there are many researchers who would argue that language is a special case of meaning—that is, without language there is no meaning, and structure preceded semantics. Particularly, Deacon, Bickerton, and Torey all express this idea in different ways. I'm partial to this point of view myself.

If you don't ride the UG train, The Symbolic Species by Terrence Deacon is a good read. Some of his biological speculation is a little questionable, but all the semiotic stuff is solid and sensible.

Yes and maybe no. All logic starts with principles that are unprovable; but this does not mean they are "outside" reason. It only means that they are principles in no need of proof, or "per se notum quoad nos", as the Scholastics would say: known to us through itself (and in need of nothing else). The first such per se notum is "being"--and not to defer, but understanding just what means turns out to be pretty complicated, so I wrote a (really overpriced but right now a whole $15 off!) book about it.

That said, I'd say there are some pretty good a posteriori reasons to prioritize human existence, not only ones which are sentimental. After all, no other known lifeform has yet to evolve capacities for language (determined by a specific grasp of symbolicity--Terry Deacon having an accessible if disputable argument about this, as well as what I think is an inaccurate interpretation of Peirce, on the whole--as opposed to speech).