A good way to make human-machine interaction more natural would be to develop a better metaphor. A computer metaphor is a familiar object or activity that your computer imitates with its commands, display arrangements, and behavior. The two main metaphors we have today are the desktop and the browser. In the desktop metaphor, the display screen mimics a typical desk; information is kept inside folders, which can be opened, closed, and slipped into other folders. With Web browsing, the metaphor is downtown window shopping: you gaze at various "storefronts," see one you like, and (click) you enter. Inside, there are more options to browse, you choose another, and again you enter. Like a linguistic metaphor, the power of a good computer metaphor is that it makes anew system you don't know behave like an old "system" with which you are familiar. This lets you use the new system and get useful results out of it easily, since you don't have to struggle learning new concepts and commands.

Human activity on the landscape can significantly contribute to soil erosion. In a natural state, vegetation serves as natural protection against erosion because the network of roots helps hold the soil in place against various erosive forces, such as wind and water. Scientists estimate that, in the United States, 30% of erosion is due to natural forces and 70% is due to human impact. Oftentimes, when people use the land for farming, the protective covering of natural vegetation is destroyed, and the erosion process speeds up. In fact, studies have shown that artificially created erosion played a big part in the downfall of many early civilizations. Poor land management practices degraded the soil until it was no longer productive enough to support the population living in the area. Early civilizations that recognized the disastrous effects of erosion used devices such as terracing the land to keep from plowing, planting, and irrigating on hillside slopes where water could wash the fertile soil away.

It used to be thought that Neanderthals were dim-witted, slouching cavemen completely covered with hair. But this reputation is based on just one fossil, which modern scholarship has proved happens to be that of an old, diseased, and injured man. He was approximately forty or forty-five years old when he died - very old for people at that time. Healthy Neanderthals probably walked erect. Objects found at Neanderthal sites show that Neanderthals could make complex tools. The characteristics of their skulls suggest that they probably could speak, although perhaps not with the full range of sounds that modern humans make. Sites also show that they did not necessarily live in caves, but, if they did, they likely altered the caves to make them more livable. Sometimes they built shelters rather than settled in caves. In 1996, scientists digging at a Neanderthal site in Slovenia announced they had found 5 what appeared to be a musical instrument, a flute made from a bear bone.

Discrimination occurs on two levels: institutional and individual. On the institutional level, discriminatory practices are embedded in the social structures of a society, whereas on the individual level, discrimination takes place during direct interactions among individuals or groups. Unlike individual discrimination, which tends to be overt, intentional, and direct, institutional discrimination si often covert and unintentional, and this invisibility makes them much harder to detect. Standardized testing in schools, for example, may exclude certain historically marginalized groups from succeeding in academic settings. Although the government may not have intentionally established testing standards that are culturally or class biased, in practice these standards tend to have a disproportionate negative effect on ethnic minority students. Furthermore, institutional discrimination often has a generational or cyclical impact on certain ethnic minority groups and therefore its consequences are as severe, if not more so, than for those suffering individual discrimination.