The Surprising Second Brain in Your Stomach

There's a "second brain" surrounding our stomach that has more neurons than a cat's brain. It is capable of controlling digestion, autonomous reflexes, memories, and even senses, leading to the idea that our gut has evolved to handle the critical action of nutrition separately from the main brain. It's thought to have come about because of the blood-brain barrier and the main brain being locked away in the skull, away from the critical action of nutrition. This explains the existence of the "butterflies in the stomach" sensation.