A 2014 article in the journal Frontiers in Psychology entitled "The Mystery of Language Evolution" addresses--among other issues--this question of "whether...animal signals help us understand the evolution of our capacity to represent words..." The authors (including the famed linguist Noam Chomsky) respond in the negative, for following reasons. First, animal signals are acquired within the "early juvenile period"--unlike words in human language, which are acquired throughout life. Moreover, "for most species, the sounds or gestures are innately specified," which is not true for words. Second, these animal signals refer to "directly observable objects or events," not to abstract concepts, as is often the case with words in human language. Third, animal vocalizations or gestures are rarely combined to "create new meaning based on new structures," whereas in human language, words are frequently combined in new ways to express new ideas. Fourth, animal utterances are "holistic" and exhibit no evidence of "complex syntactic composition derived from an inventory of discrete morphological elements." That is to say, animal utterances are not constructed like words in human language, which are made up of specific elements, such as the "s" that is added to a plural word like cats in English. Fifth, animal signals are "not marked by anything remotely resembling grammatical classes, agreement, etc." This means that animal signals lack certain common characteristics of words in human language. For example, animal gestures and utterances cannot be classified according to their grammatical function--like "verb" or "noun"--as words can be. Nor do they need to agree in number or gender, as is the case with words in many human languages.
In light of these differences between animal gestures and vocalizations on the one hand and words on the other, the authors conclude "it is not possible to empirically support a continuity thesis whereby a nonhuman animal form served as a precursor to the modern human form." In other words, there is no evidence to support the idea that words in human language are simply more sophisticated versions of animal signals which evolved over time. This reality makes an evolutionary explanation for the origin of human language all the more difficult.
Image of vervet monkey from Wikimedia Commons