Inter-Modular Interactions, Metaphor, and the 'Great Leap'
The rhetorical (philosophical) answer is that the brain of any species is unique – it’s the definition of a species. So why bother ? There are two answers; first, we are human and are, therefore, more naturally curious about our own uniqueness. Second, some traits may just be quantitatively different on a pre-existing continuum while others represent a quantum leap; which are the latter? In other words, people have an intuitive understanding of the word unique. Technically, a mouse's or pigeon's neck is as unique as a giraffe's, but only a pedant would fail to acknowledge that the latter is off – scale . The question is What are the human brain equivalents of the giraffes neck or elephants trunk? Language, especially recursiveness? Self-awareness? Laughter and humor – even though not all humans share them ?
We argue that human mental uniqueness emerged from the fortuitous co-emergence of certain novel anatomical structures and functions and equally fortuitous synergistic interactions between them. These include structures involved in intersensory abstraction (IPL and its uniquely human subdivisions; supramarginal gyrus and angular gyrus; certain frontal structures, Wernicke's area, etc.) and sensori-motor abstraction (mirror neurons). These were then exapted for higher level abstractions such as metaphor.