Mammals in the wild typically get around 40 calories of food for every calorie they spend foraging. Humans in hunter-gatherer societies like the Hadza or mixed foraging-farming societies like the Tsimane fare a bit worse, with each calorie of work spent on food production yielding around 10 calories of food. Our modern food production system violates the fundamental laws of ecology. When we include the fossil fuel energy consumed in food production, we burn 8 calories for every calorie of food we produce.
