Diamond (1993) and Graslund (2005) both refer to Chomsky’s theory of “universal grammar” as the explanation for our linguistic capabilities (Diamond, 163; Graslund, 108).  All modern-day languages are equally complex and follow the same neurologically-imposed model encompassing all grammatical possibilities (Diamond, 159-163).  “Universal grammar” suggests that all modern-day human language is derived from a single, linear linguistic development.  Diamond and Graslund both propose innovation as the driving force behind our evolutionary success.  Neanderthals did not posses our ancestor’s creative capabilities and therefore perished as a result of their inability to compete with our rapidly evolving language (Diamond, 50; Graslund, 111).  Both Diamond and Graslund suggest the complexity our of articulated speech (both vocal control and auditory variety) is due to anatomical changes in our vocal tracts and the muscle structure of our necks (Diamond 54, Graslund, 117). While Diamond does not presume any further, Graslund suggests bipedalism as the driving force of speech development (Graslund, 117). Furthermore, Graslund continues to suggest the aquatic hypothesis as the evolutionary reasoning behind bipedalism, while Diamond only mentions bipedalism in passing and holds a more conservative approach to the theories he suggests to his audience (Graslund, 118).  Overall, Graslund does not give the reader a sound explanation to many of his theories.  For example, Graslund uses an infant’s speech development and the ability to walk as his proof of the connection between bipedalism and human linguistic capabilities in context of human evolution. (Diamond, 117).  While this observation is applicable to modern day human development, it has little to no correlation to how certain apes evolved into speaking bipeds. 

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