The origin of the human mind remains one of the greatest mysteries of all times. The last 150 years since Charles Darwin proposed that species evolve under the influence of natural selection have been marked by great discoveries. However, the discussion of the evolution of the human intellect and specific forces that shaped the underlying brain evolution is as vigorous today as it was in Darwin's times. Using his background in neuroscience, the author offers an elegant, parsimonious theory of the evolution of the human mind and suggests experiments that could be done to test, refute, or validate the hypothesis.
The basis of the theory is a simple, yet fundamental question: what happens neurologically when two objects, never before seen together (say, an apple on top of a whale), are imagined together for the first time. The scientific consensus is that a familiar object, such as an apple or a whale, is represented in the brain by thousands of neurons dispersed throughout the posterior cortex. When one sees or recalls such an object, the neurons of that object’s neuronal ensemble tend to activate into synchronous resonant activity. The neuronal ensemble binding mechanism, based on the Hebbian principle “neurons that fire together, wire together,” came to be known as the binding-by-synchrony hypothesis. However, while the Hebbian principle explains how we perceive a familiar object, it does not explain the infinite number of novel objects that humans can voluntarily imagine. The neuronal ensembles encoding those objects cannot jump into spontaneous synchronized activity on their own since the parts forming those novel images have never been seen together. The author argues that to account for imagination, the binding-by-synchrony hypothesis would need to be extended to include the phenomenon of mental synthesis whereby the brain actively and intentionally synchronizes independent neuronal ensembles into one morphed image. Thus, the apple neuronal ensemble is synchronized with the whale neuronal ensemble, and the two disparate objects are perceived together. The synchronization mechanism of mental synthesis is likely responsible for many imaginative and creative traits that scientists have recognized as being uniquely human, despite not having a precise neurological understanding of the process.
How did humans acquire mental synthesis? As of 100,000 years ago, hominins had already evolved both a greater control of perception by the prefrontal cortex and a nearly modern speech-production apparatus. However the connections between the prefrontal cortex and the posterior cortex remained asynchronous; the prefrontal cortex was unable to synchronize independent neuronal ensembles, speech remained finite and non-syntactic: one word was only able to communicate one image. At that time, a single mutation delayed the ontogenetic development of the prefrontal cortex and permitted the newly invented syntactic speech to train the synchronous connections between the prefrontal cortex and the posterior cortex. This allowed the acquisition of mental synthesis and propelled humans to behavioral modernity. These behaviorally modern humans excelled at performing mental simulations, which resulted in the dramatic acceleration of technological progress; the human population exploded and humans quickly settled most habitable areas of the planet. Armed with the ability to mentally simulate any plan and then to communicate it to their companions, humans rapidly became the dominant species.
