Hunter gathers probably spent a few hours a day hunting and/or gathering and the rest of their time sitting around a fire, processing their food, making and repairing clothes, telling each other what happened while they were out hunting, teaching kids how to make tools, and playing with dogs. They had to work very hard, and it wasn't idyllic, but it also wasn't constantly stressful. Facing down a charging mammoth or lion is something your stress response is perfectly equipped to handle. Going to your job every day and overworking yourself while you're sick because you can't afford to take time off and worrying about whether your paycheck will cover this month's rent and what you'll have to do if it doesn't is from an evolutionary perspective an outside context problem.