Practice Reading for Informational Text Test 1, psg 2

DIRECTIONS: Read the two passages and then answer the questions that follow.

A Scratch Tells All

by Vaughn M. Bryant

1 Scientist Jared Diamond shocked the world with his article “The Worst Mistake in the History of the Human Race.” Diamond said that the invention of agriculture, supposedly our most important step toward a better life, was actually a catastrophe from which humans have never recovered.

2 How is this possible? Didn’t farming end starvation and famine? Didn’t it free us from having to wander the land looking for our next meal? Didn’t a dependable food source give us time to build cities, invent new technologies, and put astronauts on the moon? What about TV, cell phones, computers, and DVDs? If we still lived in caves, would they even exist?

3 Diamond is exaggerating, but he is right about one thing: Humans have paid a high price for the change to farming. The early farmers traded their good health, nutritious diets, and longer life span for shorter lives plagued by disease and for daily meals made from farm foods that provided calories but lacked many vital minerals and vitamins. Instead of eating such healthy natural foods as nuts, berries, roots, and fruit, early farmers ate the same boring starches and sugars that came from their crops of corn, barley, wheat, or rice. The change in lifestyle and diet from prefarming to farming is recorded in the archaeological record. At each site, buried skeletons tell the same story.

Deadly Sugars

4 “Teeth reflect the health status and lifestyle” of human cultures, reports Dr. Boyd Eaton and his colleagues at Emory University Medical School. This is evident in the burials at the Dickson Mounds in west-central Illinois, where people lived for thousands of years before switching to farming around AD 150. Compared with their ancestors, the first farmers had teeth with much more tooth decay and 50 percent more defects in the protective layers of tooth enamel. These new problems were caused by diets high in starch and sugar and poor in nutrition. Emory University’s George Armelagos, who studied the Dickson Mounds skeletons, also found that the life expectancy of those early farmers dropped to 19 years of age. This is one-third less than it had been among their non-farming ancestors.

5 The same story is repeated around the world. Research on skeletal remains reveals that before farming Europeans had few problems with their teeth. Pre-farming hunting and gathering societies in Europe had less than two percent tooth decay, tooth abscesses, or tooth loss caused by infections. By the early farming period, however, that percentage had risen to three and one-half percent. By Roman times, tooth decay was more than six percent. By the early 1800s, it had doubled to more than 12 percent. After the widespread use of inexpensive, refined sugar in the early 1900s, the rate of tooth decay among factory workers in England reached 70 percent.

6 Why are teeth a useful guide to health and diet? Wear patterns, scratch marks, and dental decay all tell a story about the foods we eat and how they were prepared. Many of the teeth of pre-farming peoples have high numbers of fine scratches on the enamel, probably caused by eating natural plant foods. In the teeth of early farmers, the tops of most molars are worn smooth and their enamel surfaces have coarse scratches. Most likely this was the result of chewing on bits of sand and grit in the stone-ground flour early farmers made from their crops of barley, wheat, or corn.

A Terrible Mistake

7 The most significant change in the teeth of early farming communities is the number and types of cavities. Plaque is the thick film that covers exposed tooth surfaces and forms an ideal home for acid-producing bacteria that ruin tooth enamel. Chewing natural plant foods that are coarse and high in fiber removes much of the plaque as does good brushing. Eating meat and fat does not produce any food for the enamel-eating bacteria. Sugars, on the other hand, and finely ground starch grains made from the plants grown by farmers have molecules that easily dissolve in the mouth. These molecules are then quickly absorbed into the plaque layer, where they feed millions of acid-producing bacteria. What’s more, the finely ground starch grains are easily trapped in between teeth, where they continue to feed more acid-producing bacteria. So, it is not surprising that the most common type of tooth decay among early farmers is found in between teeth. This type of decay is very rare in diets containing mostly coarse, unprocessed foods. 

8 While the change from hunters and gatherers to city folks may not have been humans’ “worst” mistake, humans have paid a very high price for that change. For 99 percent of the time we humans have lived on Earth, we have been constantly on the move and enjoyed good health and little tooth decay. Certainly, we cannot go back to being nomads, but we can learn to eat nutritious diets and save our teeth. As a common dentist’s office sign says, “You don’t have to brush all your teeth, only the ones you want to keep!”

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Hard Facts

by Joe J. Simmons III

1 What’s more destructive to teeth than fire, extreme cold, or desert heat? Read on to find the answer.

2 Teeth are the hardest substance in your body. They can withstand freezing, submersion in water, extremely dry conditions, accidents that destroy the rest of the body, and temperatures below 1600° degrees F for periods at a time. As a result, they are usually well preserved in archaeological and paleontological sites, even if other skeletal remains are not. Modern-day police often use teeth to help identify victims of accidents and foul play.

3 Teeth, however, are not indestructible. All are susceptible to decay. Also known as dental caries or cavities, tooth decay is the most common infectious disease in the world. It is caused by acids produced by certain types of bacteria that are passed from mother to child shortly after birth. These bacteria feed on exactly what humans feed on, in particular, sugars and other carbohydrates. Even the smallest traces of food in a person’s mouth can serve as a source of food for the decay-producing bacteria. 

Why Brushing Counts

4 Dentists call the accumulations of bacteria on teeth plaque, and it is in the plaque that the acidic attack and resulting cavities occur. The acids dissolve the hard, strong enamel of the tooth’s crown, and decay penetrates the tooth structure. Once into the softer inner layer, called dentine, a cavity’s development can be rapid and painful. If a cavity is left untreated, the tooth will eventually die. Abscesses—severe infections in the bone and soft tissues surrounding teeth—can also occur, and these can be lifethreatening.

5 The risk of dental decay and other infections is greatly reduced with good oral hygiene—regular brushing and flossing. Interestingly, tooth enamel can be made acid resistant if the element fluoride is incorporated into its structure. Fluoride occurs naturally in some areas with “hard” water, but is added to toothpastes and often to drinking water. Its use in modern societies has reduced dramatically the number of cavities in people who were exposed to fluoride during the formation of the enamel crowns of their teeth. This time period begins shortly after conception, when primary (baby) teeth are forming. It continues through a person’s teenage years with the complete formation of secondary, or permanent teeth.

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“A Scratch Tells All” by Vaughn M. Bryant, from DIG Magazine, Oct. 2003, copyright © 2003, Cricket Media. Used by permission. Excerpt from “Hard Facts” by Joe J. Simmons III, from DIG Magazine, Sep. 2003, copyright © 2003, Cricket Media. Used by permission.