Besides Damasio, and besides stuff by scientists like Terrence Deacon, whom I brought up here before, Clifford Geertz long ago wrote a couple of lucid articles that address these questions of language, thought, wolf-children and other feral fantasies.
Though a bit dated (including early-seventies patriarchal language, preserved below), both pieces eloquently explain the basic points, on the significance of the brain's co-evolution with language/symbol/society, echoed by others more recently. (Both pieces are in his 1973 volume, _The Interpretation of Cultures_.)
Geertz:
"Men without culture would not be the clever savages of Golding's _Lord of the Flies_ thrown back upon the cruel wisdom of their animal instincts; nor would they be the nature's noblemen of Enlightenment primitivism or even, as classical anthropological theory would imply, intrinsically talented apes who had somehow failed to find themselves. They would be unworkable monstrosities with very few useful instincts, fewer recognizable sentiments, and no intellect: mental basket cases. As our central nervous system -- and most particularly its crowning curse and glory, the neocortex -- grew up in great part in interaction with culture, it is incapable of directing our behavior or organizing our experience without the guidance provided by systems of significant symbols. What happened to us in the Ice Age is that we were obliged to abandon the regularity and precision of detailed genetic control over our conduct for the flexibility and adaptability of a more generalized, though of course no less real, genetic control over it. To supply the additional information necessary to be able to act, we were forced, in turn , to rely more and more heavily of cultural sources -- the accumulated fund of significant symbols. Such symbols are thus not mere expressions, instrumentalities, or correlates of our biological, psychological, and social existence; they are prerequisites of it. Without men, no culture, certainly; but equally, and more significantly, without culture, no men." ["The Impact of the Concept of Culture on the Concept of Man"]
"A cultureless human being would probably turn out to be not an intrinsically talented though unfulfilled ape, but a wholly mindless and consequently unworkable monstrosity. Like the cabbage it so much resembles, the Homo sapiens brain, having arisen within the framework of human culture, would not be viable outside of it. [...] The fact that the final stages of the biological evolution of man occurred after the initial stages of the growth of culture implies that the "basic," "pure," or "unconditioned," human nature, in the sense of the innate constitution of man, is so functionally incomplete as to be unworkable. Tools,hunting, family organization, and, later, art, religion, and science molded man somatically; and they are, therefore, necessary not merely to his survival but to his existential realization." ["The Growth of Culture and the Evolution of Mind"]
--M