Chapter 3: The Expensive Organ
Your brain is 2% of your body mass but burns 20% of your energy. It's the most expensive organ in nature -- and you're starving it of everything it was built to consume.
◆ Key Insights
Cooking shrank the human gut by 60%, freeing energy for brain expansion -- fire literally built the brain
Dunbar's Number (150) explains why your brain is so large: managing complex social relationships, not making tools, drove cognitive evolution
Loss aversion, optimism bias, and prospective cognition were survival advantages on the savannah -- they're liabilities in the modern world
Your best ideas come in the shower because the Default Mode Network needs idle time that constant notifications destroy
Processed food, social isolation, and 5-hour sleep nights are starving the most expensive organ in your body
Read the full chapter to understand the elegant trade-off between gut and brain that made you human -- and what happens when you break it.
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