For virtually all of evolutionary history, salts, sugars and fats were rare and precious. The only time we encountered sweetness was in the few weeks of berry season or the lucky find of a honeycomb. The phrase “worth his salt” refers to the days of Rome, when soldiers were paid in this essential mineral. And fat—concentrated, delicious calories—was only available in nuts, oils, and meats. This is why, when we encounter a bacon cheeseburger sandwiched between two Krispy Kreme donuts, we lose our minds.
