Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The Three Stages of Brain Evolution
The US developmental psychologist Stephen Porges characterized the evolution of consciousness as a transition from a state of being acted upon by the world to a state of acting upon the world. Consciousness originated when the brain evolved from the reptilian structure to the mammalian structure (using Paul MacLean's model for the evolution of the brain).
The brain of a reptile (which de facto means the brainstem and the hypothalamus) is not active, but simply reactive: it reacts to food, light, temperature. The reptilian brain increases or decreases metabolism based on the body’s needs. Matter prevails over mind.
In a mammal, instead, the brainstem and the hypothalamus command adjustments so that body temperature and metabolism are kept stable. This phenomenon enables the brain to dedicate energies to other functions. The brain of a mammal is capable of acting: mammals explore their environment looking for what they need. Mind prevails over matter.
The same argument can be made from an energetic perspective, which is reflected in the differences between the reptilian and mammalian cardiac systems. In the highly competitive world of mammals, it is necessary for the body to increase the production of energy to deal with preys and predators (hunt or run). So it is no surprise that mammals have metabolic demands four to five times that of reptiles, which makes reptiles more prone to passive feeding strategies, whereas mammals can actively hunt and graze and adapt to changing environments.
The reptilian brain is designed to use food. The mammalian brain is designed to look for food.
The structures in mammals (i.e., facial muscles, larynx) that express emotion (facial expression, vocalization) were evolution of anatomical systems of the reptiles. The resulting organization of the brainstem in mammalians fostered brain functions of attention, motion, emotion, and communication.
The development of the cortex enabled the mammalian brain to communicate emotions. Then it was just a matter of time before language and conscious thought emerged.
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