Bison and Humans

When human beings first migrated from Asia into North America at the end of the last ice age, they found an enormous, now extinct creature known as the giant long-horned bison (Bison priscus). We know that early Americans hunted these beasts because excavated skeletons of the bison bear stone spear tips. The style of the points dates them to twelve to thirteen thousand years ago, not long after the first wave of human immigrants washed south and east across the continent. These early Americans ate a variety of plants and animals, but judging from the campsite remains, they had a special taste for long-horned

bison. It was their favorite prey, perhaps because one animal filled so many stomachs.

 

 

The giant horns that gave Bison priscus its common name tell us some important things about its lifestyle. Animals with gigantic weapons on their heads usually live alone or in small groups. Animals that live in herds usually have small horns. Horns and antlers help males in several ways. Animals use these horns and antlers to fight with other members of the same species, to increase their appeal to potential mates, and to protect themselves from predators. Fossil bones suggest that giant bison used their long, outward-facing horns to injure their opponents. An individual with longer horns had a better chance of circumventing its opponents’ horns and fatally wounding them than one with shorter horns, and females probably preferred to mate with winners of these contests rather than with losers, either because they liked what they saw in the male or because they liked the territory that the male could defend from competitors.

 

 

The giant bison’s architecture served it well for thousands of years, but its body shrank and changed shape, starting about twelve thousand years ago. The timing gives us an important clue about the cause. Only two major predators, wolves and lions, had hunted giant bison for tens of thousands of years. If they caused the change, it would have happened much earlier. The big change in the bison’s environment twelve to thirteen thousand years ago was the arrival of a new predator. This one walked on two feet, hunted in cooperative bands, and carried spears with well-designed stone points. Its remarkable efficiency at hunting seems to have caused a reduction in the body size of other large mammals, too. Over the past ten thousand years, North American sheep, elk, moose, musk ox, bears, antelope, and wolves have all shrunk.

 

 

Scholars have offered various explanations for these changes, but it seems likely that these new hunters converted the giant bison’s shape and habits from virtues into liabilities. Hunters who needed to get close to their prey, such as wolves and human

beings armed with spears, preferred to attack lone individuals rather than many victims at once. Hunting punished solitary, territorial giant bison and rewarded those that stayed close together. Clumps of bison became more common and grew into herds.

 

 

Herding is a classic response to heavy predation. It brings a statistical advantage to herd members because the odds that a predator will hone in on any one individual will decrease with the size of the herd. Herds further improved odds for members

through cooperative behavior. Members warned each other of danger, and they fought off predators by joining forces (e.g. by forming a circle with vulnerable backsides to the center and dangerous horns facing the periphery).

 

But bison paid a price for herding. In a given area, the supply of food per individual declined along with the chances of being attacked. Smaller bodies probably resulted from a decline in food availability as bison crowded together. Herding changed the bison’s shape as well as size. Now survival depended on the ability to crop grass, bison’s main food, quickly. Shifting the head closer to the ground, reducing horn size, and growing a hump to cantilever, or support, the head’s weight enabled bison to graze for long periods without strain. Giant horns, which enabled males to defend territory, may also have become a liability as being able to stay close together became more valuable.

 

【Paragraph 1】

When human beings first migrated from Asia into North America at the end of the last ice age, they found an enormous, now extinct creature known as the giant long-horned bison (Bison priscus). We know that early Americans hunted these beasts because excavated skeletons of the bison bear stone spear tips. The style of the points dates them to twelve to thirteen thousand years ago, not long after the first wave of human immigrants washed south and east across the continent. These early Americans ate a variety of plants and animals, but judging from the campsite remains, they had a special taste for long-horned bison. It was their favorite prey, perhaps because one animal filled so many stomachs.

 

1. According to paragraph 1, which of the following best describes the relationship between humans twelve to thirteen thousand years ago and the giant long-horned bison

A. Humans first came to the Americas as a result of following long horned bison that were migrating from Asia to the Americas.

B. Humans in the Americas preferred hunting long-horned bison to hunting other animals.

C. Humans in the Americas were forced to migrate south and east across the continent as a result of the presence of longhorned bison.

D. Humans in the Americas generally ate plants and small animals because long-horned bison were difficult to hunt.

 

 

【Paragraph 2】

The giant horns that gave Bison priscus its common name tell us some important things about its lifestyle. Animals with gigantic weapons on their heads usually live alone or in small groups. Animals that live in herds usually have small horns. Horns and antlers help males in several ways. Animals use these horns and antlers to fight with other members of the same species, to increase their appeal to potential mates, and to protect themselves from predators. Fossil bones suggest that giant bison used their long, outward-facing horns to injure their opponents. An individual with longer horns had a better chance of circumventing its opponents’ horns and fatally wounding them than one with shorter horns, and females probably preferred to mate with winners of these contests rather than with losers, either because they liked what they saw in the male or because they liked the territory that the male could defend from competitors.

 

2. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage？

Incorrect choices change the meaning in important ways or leave out essential information.

A. Females may have chosen their mates based on the male’s ability to win contests with other males, or perhaps they decided based on territory.

B. The longer-horned opponent was more likely to win in a fight, which probably made him more attractive to females because of his physical characteristics or his ability to protect territory.

C. Males engaged in contests in which they tried to wound one another with their horns while avoiding being hit by the horns of their opponent.

D. An individual that was able to avoid its opponents’ horns had a better chance of fatally wounding them and winning the contest for territory or females.

 

3. According to paragraph 2, the fact that Bison priscus had giant horns suggests which of the following about its lifestyle

A. The bison were probably more concerned with protecting themselves from predators than with fighting each other.

B. The horns were probably more for display to attract mates than for use as actual weapons.

C. Those individuals with smaller horns probably banded together to fight the males with larger horns.

D. Individuals probably lived by themselves or with only a few other bison.

 

 

【Paragraph 3】

The giant bison’s architecture served it well for thousands of years, but its body shrank and changed shape, starting about twelve thousand years ago. The timing gives us an important clue about the cause. Only two major predators, wolves and lions, had hunted giant bison for tens of thousands of years. If they caused the change, it would have happened much earlier. The big change in the bison’s environment twelve to thirteen thousand years ago was the arrival of a new predator. This one walked on two feet, hunted in cooperative bands, and carried spears with well-designed stone points. Its remarkable efficiency at hunting seems to have caused a reduction in the body size of other large mammals, too. Over the past ten thousand years, North American sheep, elk, moose, musk ox, bears, antelope, and wolves have all shrunk.

 

4. In paragraph 3, why does the author include the information that wolves and lions “had hunted giant bison for tens of thousands of years”?

A. To emphasize how good the bison’s defenses were

B. To support the claim that only wolves and lions hunted the bison for long enough to cause changes in its evolution

C. To help explain why predation by wolves and lions cannot account for the changes that occurred in bison twelve thousand years ago

D. To introduce a discussion of how changes in bison directly affected other large animals in North America

 

 

5. Which of the following can be inferred from paragraph 3 about North American sheep, elk, moose, musk ox, bears, antelope, and wolves?

A. They have all changed as a result of hunting by humans.

B. They all originated in North America at about the same time.

C. They all contributed to the change in the bison’s environment.

D. They all contributed to the change in the bison’s size and shape.

 

【Paragraph 4】

Scholars have offered various explanations for these changes, but it seems likely that these new hunters converted the giant bison’s shape and habits from virtues into liabilities. Hunters who needed to get close to their prey, such as wolves and human beings armed with spears, preferred to attack lone individuals rather than many victims at once. Hunting punished solitary, territorial giant bison and rewarded those that stayed close together. Clumps of bison became more common and grew into herds.

 

6. According to paragraph 4, which of the following is true about humans and wolves when hunting large animals?

A. Both needed to attack their prey when their prey were outside their territory.

B. Both attacked the animals in the closest part of a herd.

C. Both preferred to attack animals that were far from others.

D. Both preferred to attack multiple animals at the same time.

 

 

【Paragraph 5】

Herding is a classic response to heavy predation. It brings a statistical advantage to herd members because the odds that a predator will hone in on any one individual will decrease with the size of the herd. Herds further improved odds for members through cooperative behavior. Members warned each other of danger, and they fought off predators by joining forces (e.g. by forming a circle with vulnerable backsides to the center and dangerous horns facing the periphery).

 

7. Which of the following is NOT one of the reasons given in paragraph 5 for why herding is a classic response to heavy predation？

A. Herd members can teach one another strategies for avoiding predators.

B. Herd members can alert one another to approaching predators.

C. Herd members can fight off predators together.

D. Being in a herd reduces the chance that any particular individual will be a target.

 

 

【Paragraph 6】

But bison paid a price for herding. In a given area, the supply of food per individual declined along with the chances of being attacked. Smaller bodies probably resulted from a decline in food availability as bison crowded together. Herding changed the bison’s shape as well as size. ■Now survival depended on the ability to crop grass, bison’s main food, quickly. ■Shifting the head closer to the ground, reducing horn size, and growing a hump to cantilever, or support, the head’s weight enabled bison to graze for long periods without strain. ■Giant horns, which enabled males to defend territory, may also have become a liability as being able to stay close together became more valuable. ■

 

8. According to paragraph 6, bison in herds needed to be able to crop grass quickly because

A. the amount of food available for an individual had decreased

B. the bison body had become smaller

C. the chances of being attacked by a predator had increased

D. bison had grown a hump to support the head’s weight

 

9. Look at the four squares【■】that indicate where the following sentence could be added to the passage.

In sum, by forcing bison to live in herds, humans encouraged the development of a new kind of bison, the short

horn, humpbacked bison that we know today.

Where would the sentence best fit？

 

 

10. 【Directions】An introductory sentence for a brief summary of the passage is provided below. Complete the summary

by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong

in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This

question is worth 2 points.

Hunting by humans changed bison’s body structure and the mode of living.

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Answer Choices

A. Judging from campsite remains, the first wave of immigrants to North America carried with them hunting tools they had successfully used to hunt large animals in Asia.

B. Fossil bones suggest that several species of the long-horned bison once existed in North America, but by the time humans arrived, most of them had become extinct.

C. The size of the bison’s horns suggest that individuals lived alone or in small groups, a habit that made them attractive prey for human hunters.

D. The bison began living in herds, which would have provided protection from hunters but also decreased the amount of food available for each individual.

E. Early Americans preferred hunting long-horned bison for their horns which could be used to create sharp spear tips for hunting other large animals such as moose and musk ox.

F. When bison began to live close together, this led to other adaptations in size and shape necessary for survival.

 

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