Seven and a Half Lessons About the Brain

1/2. Your Brain is Not For Thinking

• During the Cambrian period (500m ya), something new and significant appeared on the evolutionary scene: hunting. Somewhere, somehow, one creature became able to sense the presence of another creature and deliberately ate it. Animals had gobbled one another before, but now the eating was more purposeful. Hunting didn't require a brain, but it was a big step toward developing one.
• Creatures who could better sense their surroundings were more likely to survive and thrive. The amphioxus may have been a master of its environment, but it couldn't sense that it had an environment. These new animals could.
• Once creatures could sense at a distance and make more sophisticated movements, evolution favored those who perform these tasks efficiently. If they chased a meal but moved too slowly, something else caught the meal and ate it first. If they burned up energy fleeing from a potential threat that never arrived, they wasted resources that they might have needed later. Energy efficiency was the key to survival.
• When it came to body budgeting, prediction beat reaction. A creature that prepared its movement before the predator struck was more likely to be around tomorrow than a creature that awaited a predator's pounce. Creatures that predicted correctly most of the time, or made nonfatal mistakes and learned from them, did well. those that frequently predicted poorly, missed threats, or false-alarmed about threats that never materialized didn't do so well. They explored their environment less, foraged less, and were less likely to reproduce.
• The scientific name for body budgeting is allostasis. It means automatically predicting and preparing to meet the body's needs before they arise.
• The value of any movement is intimately bound up with body budgeting by allostasis.
• Newer animals developed intricate internal systems, like a cardiovascular system with a heart that pumps blood, a respiratory system that takes in oxygen and eliminates carbon dioxide, and an adaptable immune system that fights infection. Systems like these made body budgeting much more challenging, less like a single bank account and more like the accounting department of a sizable company. These complex bodies needed something more than a handful of cells to ensure that water and blood and salt and oxygen and glucose and cortisol and sex hormones and dozens of other resources were all regulated well to keep a body running efficiently. They needed a command center. A brain.
• Human brains efficiently supervise over 600 muscles in motion, balances dozens of different hormones, pumps blood at a rate of 2k gallons per day, regulates the energy of billions of brain cells, digests food, excretes waste, and fights illness, all of it nonstop for approx 72yrs.
• Your body budget is like thousands of financial accounts in a giant multinational corporation, and you have a brain that's up to the task. And all your body budgeting takes place in a massively complicated world made even more challenging by the other brains-in-bodies that you share it with.
• Your brain's most important job is not rationality, emotion, imagination, creativity, or empathy. It is to control your body - manage allostasis - by predicting energy needs before they arise so you can efficiently make worthwhile movements and survive.
• Your brain's most important job is not thinking. It's running a little worm body that has become very, very complicated.

1. You Have One Brain (Not Three)

• The triune brain idea says that the human brain is make up of three layers:
  • The deepest layer, the lizard brain, is for surviving.
  • The middle layer, the limbic system, is for feeling
  • The outermost layer, the neocortex, is for thinking.
• It is one of the most successful and widespread errors in all of science. By the 1990s, experts had completely rejected the idea of a three-layered brain.
• It turns out that as brains become larger over evolutionary time, they reorganize.
• Scientists have recently discovered that the brains of all mammals are built from a single manufacturing plan, and most likely, the brains of reptiles and other vertebrates follow that same plan.
• The biological building blocks are the same, what differs is the timing. For example, the stage that produces neurons for the cerebral cortex in humans runs for a shorter time in rodents and a much shorter time in lizards, so your cerebral cortex is large, a mouse's is smaller, and an iguana's is tiny (or possibly non-existant).
• If a monkey's brain could grow to human size, its cerebral cortex would be the same size as ours. Elephants have much more cerebral cortex than we do, but so would an elephant-sized human brain.
• The real story is that during the course of evolution, certain genes mutated to cause particular stages of brain development to run for longer or shorter times, producing a brain with proportionally bigger or smaller parts.
• Your brain is not more evolved than a rat or lizard brain, just differently evolved.
• What we call mental illnesses may be rational body-budgeting for the short term that's out of sync with the immediate environment, the needs of other people, or your own best interests down the road.
• Rational behavior, therefore, means making a good body-budgeting investment in a given situation.

2. Your Brain is a Network

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3. Little Brains Wire Themselves to Their World

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4. Your Brain Predicts (Almost) Everything You Do

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5. Your Brain Secretly Works with Other Brains

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6. Brains Make More than One Kind of Mind

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7. Our Brains Can Create Reality

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Epilogue

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