This is my experience, that the human brain is still organically evolving in the direction of the great mystics, in the same direction as the great geniuses. For this evolution a certain type of life is necessary.

The human brain became large by natural selection (who knows why, but presumably for good cause). Yet surely most “things” now done by our brains, and essential both to our cultures and to our very survival, are epiphenomena of the computing power of this machine, not genetically grounded Darwinian entities created specifically by natural selection for their current function.

The brain is a complex system, but that doesn’t mean it’s incomprehensible. Our neural circuits were carved by natural selection to solve problems that our ancestors faced during our species’ evolutionary history. Your brain has been molded by evolutionary pressures just as your spleen and eyes have been. And so has your consciousness. Consciousness developed because it was advantageous, but advantageous only in limited amounts.

For more than 2 million years, human neural networks kept growing and growing, but apart from some flint knives and pointed sticks, humans had precious little to show for it. What then drove forward the evolution of the massive human brain during those 2 million years? Frankly, we don’t know.

Evolution doesn't design things... The brain is... like a big, old house with piecemeal renovations done on every floor, and less like new construction.

The brain is a mystery—it has been—and still will be. Not that we do not know many facts about it. The facts we know have indeed greatly multiplied in recent years, but they all fail to give us a key to the mystery of how it creates—if it does create—our thoughts and feelings; that is, said more concisely though less concretely, our mind.

The trouble is, the human brain isn’t designed to make us happy and fulfilled. It’s designed to make us survive. This two-million-year-old organ is always looking for what’s wrong, for whatever can hurt us, so that we can either fight it or take flight from it. If you and I leave this ancient survival software to run the show, what chance do we have of enjoying life?

Does anybody honestly believe that human progress originates in the composite brain of the majority and not in the brain of the individual personality? Or may it be presumed that for the future human civilization will be able to dispense with this as a condition of its existence? But may it not be that, to-day, more than ever before, the creative brain of the individual is indispensable?

There is the growing influence of biology and the application of biological principles to the human faculties, thought among the rest. Man is said to have brains because they enable him to survive. Intelligence is construed as an organic function and reason as developed or evolved intelligence.

Evolutionary psychologists suggest that, just as the eye is an evolved organ for seeing, and the wing an evolved organ for flying, so the brain is a collection of organs (or 'modules') for dealing with a set of specialist data-processing needs.

We have to face the fact that we are the descendants of apelike ancestors. The truth, at first sight, is often ugly and repulsive to our personal feelings, but when it is the truth, its ultimate effects on us are always salutary. ...
... Man's brain does not stand as a thing apart; it is the culmination of an ascending series. There is no part of it and no function manifested by it that cannot be traced to humble beginnings lower in the animal scale. And what we postulate for man's brain we must in all justice apply to that of the ape, the dog, and all other beasts.

The huge human brain, approximately 1,350 cubic centimeters, is the most complex organic structure in the known world. Understanding the human mind/brain mechanisms in evolutionary perspective is the goal of the new scientific discipline called evolutionary psychology. Evolutionary psychology focuses on four key questions: (1) Why is the mind designed the way it is—that is, what causal processes created, fashioned, or shaped the human mind into its current form? (2) How is the human mind designed—what are its mechanisms or component parts, and how are they organized? (3) What are the functions of the component parts and their organized structure—that is, what is the mind designed to do? (4) How does input from the current environment interact with the design of the human mind to produce observable behavior?

The neurobiologist Harry Jerison has made a long study of the trajectory of brain evolution since the advent of life on dry land. ...the origin of new faunal groups is usually accompanied by a jump in the relative size of the brain, known as encephalization. ...the first archaic mammals... were equipped with brains four to five times bigger than the average reptilian brain... primates are twice as encephalized as the average mammal. Within primates, the apes... are some twice the average size. And humans are three times as encephalized as the average ape.

In its evolution from a more primitive nervous system, the brain, as an organ with ten or more billion neurons and many more connections between them must have changed and grown as a result of many accidents.