ABSTRACT
When a detective reconstructs a crime or a palaeontologist makes a model of an extinct creature from a few fragments, there is an obligation to use all the evidence available but a need to go beyond that evidence. An attempt to see how the pieces fit together may lead to new insights, and show where further detail must be sought. The RS theory suggests that there is only one specific influence on human handedness, something that induces a cerebral asymmetry in favour of the left hemisphere during foetal growth. In order to isolate this one key feature, a great deal of ground must be cleared, and many overlain theoretical constructions removed. This chapter attempts to summarise and reconstruct by asking what are the facts about the RS theory, how do the proposed mechanisms (chance and RS +) operate, and finally why. The last question, the motivation for the crime, or the evolutionary pressures at work must go beyond the evidence to create a “just so” story for the evolution of human speech.
