The human brain is not only large relative to human body size, it is also lateralized,that is, it has specialized functions in each of the two hemispheres. (More details arepresented in Chapter 12.) Those functions that control the motor movements involvedin complex vocalization (speaking) and object manipulation (making or using tools)are very close to each other in the left hemisphere of the brain. That is, the area of themotor cortex that controls the muscles of the arms and hands is next to the articulatorymuscles of the face, jaw and tongue. It may be that there was an evolutionary connection between the language-using and tool-using abilities of humans and that both wereinvolved in the development of the speaking brain. Most of the other speculativeproposals concerning the origins of speech seem to be based on a picture of humansproducing single noises to indicate objects in their environment. This activity mayindeed have been a crucial stage in the development of language, but what it lacks isany structural organization. All languages, including sign language, require the organizing and combining of sounds or signs in specific arrangements. We seem to havedeveloped a part of our brain that specializes in making these arrangements.