The Unitary Hypothesis: A common neural circuitry for novel manipulations, language, plan- ahead, and throwing?
Plan-ahead becomes necessary for those movements which are over-and-done in less time than it takes for the feedback loop to operate. Natural selection for one of the ballistic movements (hammering, clubbing, and throwing) could evolve a plan-ahead serial buffer for hand-arm commands that would benefit the other ballistic movements as well. This same circuitry may also sequence other muscles (children learning handwriting often screw up their faces and tongues) and so novel oral-facial sequences may also benefit (as might kicking and dancing). An elaborated version of the sequencer may constitute a Darwin Machine that spins scenarios, evolves sentences, and facilitates insight by offline simulation. An example is given of an evolutionary scenario from an apelike ancestor, demonstrating the transition behaviors and growth curve considerations that any such theory needs to have; this particular scenario (involving throwing improvements) also suggests an explanation for the puzzling design of the Acheulean "handle."