from natural sources: from the food that they eat, or from sunshine through photosynthesis. Some organisms derive the energy they need through oxidation of inorganic compounds. Because of these natural mechanisms, these species have everything they need for survival, without requiring clothing or shelter, or other types of goods. We can see how different humans are from other animals by comparing ourselves to large primates such as chimpanzees. Large primates spend much of their day gathering and eating raw food. They are not as intelligent as humans, and they mostly live in trees, so as to be able to avoid predators. This limits their choice of food supply. Their total number is far smaller than humans, because they need to stay in habitats to which they are adapted. The number of large primates varies by species (100,000 to 200,000 chimpanzees, about 130,000 gorillas, and fewer than 250,000 Gelada baboons according to the National Primate Research Center ), but is always far fewer than the 7 billion humans in the world. The shift away from behavior similar to that of other primates seems to have started after humans learned to control fire and learned to cook food. Chris Organ and others have shown that for a primate the size of humans, cooking food decreases the amount of time that must be spent chewing food from 48% of daily activity to 4.7% of daily activity. With so much more free time, the way an animal spends its time can change dramatically. Those