Because early humans had to chew up plants to get enough calories to survive, their mouths contained an extra row of molar teeth. Today, however, only 5 percent of the population has a healthy set of these third molars, or wisdom teeth. Many people just have them removed. When the human diet consisted of more plant matter than animal protein, the appendix helped digest the plant matter. Now, though, this narrow, muscular tube is not only useless, it can also cause problems; every year, more than 300,000 Americans must get it removed. The coccyx, the fused vertebrae at the base of the spine, is the useless remainder of the tail that early humans lost as they evolved, and surgical removal of the coccyx has no effect on the body's performance. Like the coccyx, human body hair once had a function. Hair on the chest and back helped keep early humans warm while eyebrows kept sweat out of the eyes. Now most of the hair left on the modern human body serves no function. A trio of ear muscles once allowed early humans to move their ears just as dogs and rabbits do. Although modern humans still have these muscles, we don't use them unless we make a conscious effort to learn how to wiggle our ears. Several other small muscles in the body, which were once important for actions like hanging, climbing, and grasping with the feet, are still present in the majority of humans, but they, too, no longer serve any function. (Source of information: Jocelyn Selim, "Useless Body Parts," Discover, June 2004, pp. 42-46.)

Implied main idea:

a. Early humans were more like animals than modern humans are.

b. Quite a few human body parts are now useless.

c. Many body parts cause problems for modern humans and have to be removed.

d. The human body offers much evidence that humans evolved from apes.

People who are exposed to a large increase in steady, prolonged background noise experience lasting elevations in their blood pressure. One study, for example, found that children who attended school near the busy, noisy Los Angeles International Airport had higher blood pressure than children attending quieter schools. If the noise is not just loud but also intermittent, those exposed to it experience symptoms of psychological distress. In a study of people living near a newly opened highway, for instance, 84 percent of those interviewed reported that were still irritated by the sound of the traffic even after a year of exposure. In other words, the sounds of the highway never receded into background noise. Several studies have shown that this noise-induced irritability can lead to increased aggression and decreased helping behavior. If sounds are not only loud and intermittent but also unpredictable, people tend to experience both behavioral and physiological symptoms of stress. For example, subjects in laboratory experiments who were exposed to noise of this type could not cope well with frustrating tasks. Their ability to perform tasks that required sustained attention to detail also suffered; in one of these studies, people subjected to loud, unpredictable noises made numerous errors as they completed proofreading tasks and tried to solve difficult puzzles. (Sources of information: Robert H. Frank, "How Not To Buy Happiness," Daedalus, Vol. 133, Issue 2, http://mitpress.mit.edu, pp. 69-79; Berglund, B., & Lindvall, T. (Eds.). "Community Noise," Archives of the Center for Sensory Research, 1995, 2(1), 1-195, http://www.nonoise.org/library/whonoise/whonoise.htm#7.6.1.2)

Implied main idea:

a. Noise elevates stress and damages health.

b. Stress is very harmful to the health.

c. America is a very noisy place.

d. People who live in noisy areas tend to be stressed out and irritable.

In many cultures, the elderly are not only respected but also revered. In Native American, Hispanic, and Asian societies, for example, older people are cherished for their knowledge, experience, and wisdom. In mainstream American culture, however, the media feeds anxieties about aging by bombarding citizens with advertisements for creams, pills, cosmetics, hair color, diet supplements, and other products that will ward off aging and make people look and feel younger. The general population often stereotypes elderly people as slow, feeble, cranky, and burdensome. Many taxpayers resent the cost of entitlement programs, such as social security and Medicare, which benefit senior citizens. Even professionals tend to have a low opinion of the elderly. Medical students use nicknames such as "vegetable" and "Gork" (short for "God only really knows" the cause of the person's symptoms) to describe elderly patients. Very few of these students choose geriatrics for their specialty. Most doctors do not devote as much time and energy to their elderly patients as they do to their younger patients. And when elderly people become depressed, their doctors are more likely to prescribe drugs rather than send them to psychotherapists because they believe that older people are too set in their ways to be able to work through their problems. (Source of information: Kelvin L. Siefert et al., Lifespan Development, 2nd ed., Boston: Houghton Mifflin, 2000, p. 590.)

Implied main idea:

a. Many cultures respect and honor the elderly.

b. Americans should respect and honor elderly citizens.

c. Americans tend to be meaner and more disrespectful than people of other cultures.

d. Many Americans fear aging and are prejudiced against the elderly.

Are "third parties," the minor political parties with beliefs that differ radically from those of the Democrats and Republicans, making any progress in their quest to change how our country is run? In 2004, 210 members of the Green Party, a third party that has been in existence since 1984, held office in twenty-seven states and the District of Columbia. Greens also held offices that included city council positions in cities such as Santa Monica, California; Chapel Hill, North Carolina; and Madison, Wisconsin. On the city council of the town of Arcata, California, Greens actually held a majority of the seats. Ralph Nader, the Green Party's candidate for president in both 1996 and 2000, received almost 2. 9 million popular votes in the 2000 presidential election. Members of the New Party, another third party begun in 1992, have also succeeded in being elected to local offices, winning 300 of its first 400 political races in states like Arkansas, Wisconsin, and Maryland. The most successful of the third parties has been the Libertarian Party, which was formed in 1972. In 2004, 581 members of this party held office, with significant impact in California, New Hampshire, and Pennsylvania. The Libertarian Party has also been the only third party to have its candidates on the ballots in all fifty states in every U.S. presidential election since 1980. (Source of information: Ann O'M. Bowman and Richard C. Kearney, State and Local Government, 5th ed., Boston: Houghton Mifflin, 2002, p. 118.)

Implied main idea:

a. Third parties are quite different from the two major political parties.

b. The Libertarian Party is the most successful of all of the third parties.

c. Third parties are having some success getting their candidates elected.

d. During the last few decades, third parties have become as successful as the two major political parties.

Researchers have long debated whether it's healthier to be slim or physically fit. One recent study conducted at Brigham and Women's Hospital in Boston examined data on 38,000 women 45 and older, whose weight, height, and physical activity were recorded for about seven years. The researchers found that women who were overweight were three times more likely than normal-weight women to develop diabetes. Even walking four or more hours per week did not lower the overweight women's risk of getting diabetes. In another study by the University of Florida, researchers examined 906 women who had been tested for possible heart problems. They found that an obese woman who was physically fit, with a strong cardiovascular system, had a low risk of developing heart disease. But they also discovered that a slim woman who was not physically fit had a relatively high risk of developing heart disease. (Source of information: Anita Manning, "Slimness vs. Cardiovascular Fitness: Which is More Crucial?" USA Today, September 8, 2004, p. 9D.)

Implied main idea:

a. It's healthier to be slim than physically fit.

b. It's healthier to be physically fit than slim.

c. Some research suggests that women who want to avoid certain major health risks may need to stay slim as well as fit.

d. Overweight people cannot be physically fit.