In this very interesting article, Martin Sereno argues that rather than evolving out of inflexible, hardwired emotion-linked calls, language may have evolved out of complex, flexible learned vocalization patterns which at first had no meaning attached to them (something like birdsong).
Sereno, M. I.(2005) Language origins without the semantic urge. Cognitive Science Online, 3, pp. 1-12.
Read on for the abstract.
Abstract: Despite the paucity of direct evidence about the origin of human language, the great intrinsic interest in this question has made it difficult for writers to resist speculating about it (Harnad et al., eds., 1976; Merlin, 1991; Deacon, 1997; Jablonski and Aiello, eds., 1998; King, ed., 1999; Knight et al., eds., 2000). This article attempts to bring a fresh perspective on this old question, using an analogy with the origin of cellular coding systems and applying it to what we know about the evolution of vocal behavior in animals. In other places (Sereno, 1991b), I have argued that DNA and protein based life and language based human thought may have enough in common as the only two naturally occurring examples of a code-using system to make it useful to take an analogical look at one system in order to make predictions about the other. Rather than rehearsing those arguments, I will only visit two jumping off points reached while developing that analogy: the difference between origin and evolution, and the foundational role of an intermediate string of “symbol representation” segments with properties partway between symbol and meaning.