Seven and a Half Lessons About the Brain

Imagine the earliest creatures on Earth, tiny and simple, drifting in ancient oceans. One such creature, barely two inches long, had no eyes, no ears, and a nervous system so rudimentary it was barely a brain at all. This creature, an amphioxus, lived about 550 million years ago, and its survival depended not on complex thought but on managing its body’s basic needs efficiently. Its nervous system was a direct link between sensing and moving, a simple budgeting tool for energy and survival.

Fast forward through millions of years, and brains have grown massively more complex, yet the core mission remains the same: to keep the body alive and well by managing resources like water, salt, and glucose. This process, called allostasis, is like a financial budget for your body. Your brain constantly predicts what your body will need and prepares accordingly, investing energy wisely to ensure survival and reproduction.

This insight challenges the common belief that the brain evolved primarily to think or reason. Instead, thinking, feeling, and imagining are all byproducts of a deeper, fundamental task: running a highly complicated body. The brain’s ability to predict and budget resources efficiently is what allowed animals to move from simple creatures like amphioxus to the complex beings we are today.

Consider the Cambrian period, when hunting emerged. Creatures needed to sense threats and opportunities from afar and move efficiently without wasting precious energy. Those that predicted well survived; those that didn't, perished. This evolutionary pressure shaped brains into highly efficient budgeting organs.

So, the next time you marvel at your ability to think or solve problems, remember that beneath it all, your brain is deeply committed to managing your body’s survival budget. This foundational understanding opens the door to exploring how our brain’s complex network supports this mission, which is the journey we will continue next.