In your own words, what is a sharecropper and a braceros?

Give an example of a situation in which an individual's pursuit of economic self-interest may not benefit but instead harm the rest of society

The controlled use of fire by hominids: (a) limited the expansion of hominids into certain environments, such as dry grasslands. (b) decreased the amount of food energy available in the hominid diet. (c) contributed to geographical expansion and food production techniques in positive ways. (d) has been shown to contribute little to the digestive process of hominids.

Why are people in history willing to fight in conflicts against a more powerful oppressor?