Like all our organs, the brain has evolved, increasing in complexity and information content, over millions of years. Its structure reflects all the stages through which it has passed. The brain evolved from the inside out.
According Paul MacLean, the higher functions of the human-brain evolved in 4 successive stages.
- Deep inside is the oldest part, the brainstem, which conducts the basic biological functions, including the rhythms of life – heartbeat and respiration.
- Capping the brainstem is the R-complex (R stands for reptile), which evolved in our reptilian ancestors. Deep inside the skull of every one of us there is something like the brain of a snake that gives us the traits of aggression, ritual, territoriality and social hierarchy.
- Surrounding the R-complex is the mammalian brain, which evolved in ancestors who were mammals but not yet monkeys. It is a major source of our moods and emotions, of our concern and care for the young.
- And on the outside, living in uneasy friendship with the more primitive brains beneath, is the cerebral cortex, which evolved in our ape-like ancestors. Comprising more than two-thirds of the brain mass, it is here that we have ideas and inspirations, here that we read and write, here that we plan, do mathematics and compose music.
Civilization is a product of the cerebral cortex.**
A simple animation illustrating the layer-upon-layer addition during evolution:
For some reason, I found this idea to be similar to the concepts of inheritance & override in Object-Oriented Programming.
The following image should assist in driving home the idea of the Evolutionary Trajectory of the Triune brain:
Much of what we call Civilization is due to self-control mechanisms that evolved in the brain of our ape-like ancestors. Gratification-Postponement in humans, or willpower, originates in pre-frontal cortex.
(link to the source blog)
The other day, I was searching for an infographic that visually clarified the common misconception when it comes to evolution – “If man evolved from monkey, why are there still monkeys around us?” I found this infographic helpful. It’s part of a bigger and much more detailed image.
And this what Wikipedia has to say on the Triune hypothesis:
https://en.wikipedia.org/wiki/Triune_brain#Lay_interest
While technically inaccurate as an explanation for brain activity, the Triune hypothesis remains one of very few approximations of the truth we have to work with.
Here’s more on Evolutionary Ancestry from Richard Dawkins’ book – The Magic of Reality :
Thought Experiment –
Imagine if you had the photograph of each of your male-ancestor. Starting with the photo of your father, if you start stacking on top of it the photo of your grandfather and then the photo of your great-grandfather and so on, how tall would the stack be?
This vertical stack of photographs would dwarf the Empire State Building!
To assist imagination, let’s instead stack the photographs horizontally. This is how it would look. And yes, if you’d then look at the photo of your male-ancestor who lived 410 million years ago, he would’ve probably looked fish-like!
References
- “Cosmos“ by CARL SAGAN
- “The Magic of Reality” by Richard Dawkins
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