Table of Contents
Passage
Mammoth is any species of the extinct genus Mammuthus, proboscideans commonly equipped with long, curved tusks and in northern species, a covering of long hair. They lived from the Ptiocene epoch from around 5 million years ago, into the Hotocene at about 4,500 years ago, and were members of the family Elephantidae, which contains, along with mammoths, the two genera of modern elephants and their ancestors.
A. Like their modern relatives, mammoths were quite large. The largest known species reached heights in the region of 4m at the shoulder and weights up t0 8 tonnes, while exceptionally large males may have exceeded 12 tonnes. However, most species of mammoth were only about as large as a modern Asian elephant. Both sexes bore tusks. A first, small set appeared at about the age of six months and these were replaced at about 18 months by the permanent set. Growth of the permanent set was at a rate of about l t0 6 inches per year. Based on studies of their close relatives, the modem elephants, mammoths probably had a gestation period of 22 months, resulting in a single calf being born. Their social structure was probably the same as that of African and Asian elephants, with females living in herds headed by a matriarch, whilst hulls lived solitary lives or formed loose groups after sexual maturity.
B. MEXICO CITY-Although it’s hard to imagine in this age of urban sprawl and automobiles, North America once belonged to mammoths, camels, ground sloths as large as cows, bear-size beavers and other formidable beasts. Some 11,000 years ago, however, these large bodied mammals and others-about 70 species in all-disappeared. Their demise coincided roughly with the arrival of humans in the New World and dramatic climatic change-factors that have inspired several theories about the die-off. Yet despite decades of scientific investigation, the exact cause remains a mystery. Now new findings offer support to one of these controversial hypotheses: that human hunting drove this megafaunal menagerie to extinction. The overkill model emerged in the 1960s, when it was put forth by Paul S. Martin of the University of Arizona. Since then, critics have charged that no evidence exists to support the idea that the first Americans hunted to the extent necessary to cause these extinctions. But at the annual meeting of the Society of Vertebrate Paleontology in Mexico City last October, paleoecologist John Alroy of the University of California at Santa Barbara argued that, in fact, hunting-driven extinction is not only plausible, it was unavoidable. He has determined, using a computer simulation that even a very modest amount of hunting would have wiped these animals out.
C. Assuming an initial human population of 100 people that grew no more than 2 percent annually, Alroy determined that if each band of, say, 50 people killed 15 to 20 large mammals a year, humans could have eliminated the animal populations within 1,000 years. Large mammals in particular would have been vulnerable to the pressure because they have longer gestation periods than smaller mammals and their young require extended care.
D. Not everyone agrees with Alroy’s assessment. For one, the results depend in part on population-size estimates for the extinct animals-figures that are not necessarily reliable. But a more specific criticism comes from mammalogist Ross D. E. MacPhee of the American Museum of Natural History in New York City, who points out that the relevant archaeological record contains barely a dozen examples of stone points embedded in mammoth bones (and none, it should be noted, are known from other megafaunal remains)-hardly what one might expect if hunting drove these animals to extinction. Furthermore, some of these species had huge rangesthe giant Jefferson’s ground sloth, for example, lived as far north as the Yukon and as far south as Mexicowhich would have made slaughtering them in numbers sufficient to cause their extinction rather implausible, he says.
E. MacPhee agrees that humans most likely brought about these extinctions (as well as others around the world that coincided with human arrival), but not directly. Rather he suggests that people may have introduced hyperlethal disease, perhaps through their dogs or hitchhiking vermin, which then spread wildly among the immunologically naive species of the New World. As in the overkill model, populations of large mammals would have a harder time recovering. Repeated outbreaks of a hyperdisease could thus quickly drive them to the point of no return. So far MacPhee does not have empirical evidence for the hyperdisease hypothesis, and it won’t be easy to come by: hyperlethal disease would kill far too quickly to leave its signature on the bones themselves. But he hopes that analyses of tissue and DNA from the last mammoths to perish will eventually reveal murderous microbes.
F. The third explanation for what brought on this North American extinction does not involve human beings. Instead, its proponents blame the loss on the weather. The Pleistocene epoch witnessed considerable climatic instability, explains paleontologist Russell W. Graham of the Denver Museum of Nature and Science. As a result, certain habitats disappeared, and species that had once formed communities split apart. For some animals, this change brought opportunity. For much of the megafauna, however, the increasingly homogeneous environment left them with shrinking geographical ranges-a death sentence for large animals, which need large ranges. Although these creatures managed to maintain viable populations through most of the Pleistocene, the final major fluctuation-the so-called Younger Dryas eventpushed them over the edge, Graham says. For his part, Alroy is convinced that human hunters demolished the titans of the Ice Age. The overkill model explains everything the disease and climate scenarios explain, he asserts, and makes accurate predictions about which species would eventually go extinct. “Personally, I’m a vegetarian,” he remarks, “and I find all of this kind of grossbut believable.”
Questions
Questions 14-20 Summary Complete the following summary of the paragraphs of Reading Passage, using no more than three words from the Reading Passage for each answer. Write your answers in boxes 14-20 on your answer sheet.
The reason why big size mammals extincted 11,000 years ago is under hot debate. First explanation is that 14 …………………. of human made it happen. This so called 15 …………………. began from 1960s suggested by an expert, who however received criticism of lack of further information. Another assumption is that deadly 16 …………………. from human causes their demises. MacPhee, who supported this idea, suggested that he required 17 …………………. to testify its validity. Graham proposed a third hypothesis that 18 …………………. in Pleistocene epoch drove some species disappear, reduced 19 …………………. posed a dangerous signal to these giants, and 20 …………………. finally wiped them out.
Questions 21-26 Use the information in the passage to match the people (listed A-C) with opinions or deeds below. Write the appropriate letters A-C in boxes 21-26 on your answer sheet.
NB you may use any letter more than once
A John Alroy
B Ross D. E. MacPhee
C Russell W. Graham
21 Human hunting well explained which species would finally disappear.
22 Further grounded proof needed to explain human’s indirect impact on mammals.
23 Over hunting situation has caused the die-out of large mammals.
24 Illness rather than hunting caused extensive extinction.
25 Doubt raised through the study of several fossil records.
26 Climate shift is the main reason of extinction.
Answers
Below are the answers, key words, synonyms and full explanations for the IELTS Reading passage Mammoth Kill (Passage 2, Questions 14–26).
Questions 14–20: Summary Completion (NO MORE THAN THREE WORDS)
14. First explanation is that ______ of humans made it happen.
Answer: hunting
Key words: human hunting drove this megafaunal menagerie to extinction
Synonyms: = “new findings offer support to one of these controversial hypotheses: that human hunting drove this megafaunal menagerie to extinction”
Explanation: Paragraph B: the first theory is that human hunting caused the die-off → hunting.
15. This so-called ______ began in the 1960s, suggested by an expert.
Answer: overkill model
Key words: The overkill model emerged in the 1960s
Synonyms: = “The overkill model emerged in the 1960s, when it was put forth by Paul S. Martin”
Explanation: Paragraph B names this hunting theory the “overkill model,” from the 1960s → overkill model.
16. Another assumption is that a deadly ______ from humans caused their demise.
Answer: disease (hyperdisease)
Key words: people may have introduced hyperlethal disease … Repeated outbreaks of a hyperdisease
Synonyms: deadly disease = hyperlethal disease = “people may have introduced hyperlethal disease, perhaps through their dogs or hitchhiking vermin”
Explanation: Paragraph E: MacPhee’s theory is that humans introduced a deadly disease → disease/hyperdisease.
17. MacPhee suggested that he required ______ to prove its validity.
Answer: empirical evidence
Key words: MacPhee does not have empirical evidence for the hyperdisease hypothesis
Synonyms: to prove validity = to support the hypothesis = “So far MacPhee does not have empirical evidence for the hyperdisease hypothesis”
Explanation: Paragraph E: he still lacks (and needs) empirical evidence → empirical evidence.
18. Graham proposed that ______ in the Pleistocene epoch drove some species to disappear.
Answer: climatic instability
Key words: The Pleistocene epoch witnessed considerable climatic instability
Synonyms: = “The Pleistocene epoch witnessed considerable climatic instability, explains paleontologist Russell W. Graham”
Explanation: Paragraph F: Graham blames climatic instability → climatic instability.
19. Reduced ______ posed a dangerous signal to these giants.
Answer: geographical ranges
Key words: the increasingly homogeneous environment left them with shrinking geographical ranges—a death sentence for large animals
Synonyms: reduced = shrinking = “left them with shrinking geographical ranges—a death sentence for large animals, which need large ranges”
Explanation: Paragraph F: shrinking geographical ranges doomed the large animals → geographical ranges.
20. And the ______ finally wiped them out.
Answer: Younger Dryas event
Key words: the final major fluctuation—the so-called Younger Dryas event—pushed them over the edge
Synonyms: finally wiped out = pushed over the edge = “the final major fluctuation—the so-called Younger Dryas event—pushed them over the edge”
Explanation: Paragraph F: the Younger Dryas event delivered the final blow → Younger Dryas event.
Questions 21–26: Matching People (A–C)
A – John Alroy | B – Ross D. E. MacPhee | C – Russell W. Graham
21. Human hunting well explained which species would finally disappear.
Answer: A (John Alroy)
Key words: makes accurate predictions about which species would eventually go extinct
Synonyms: explained which species disappear = accurate predictions about which species go extinct = “The overkill model … makes accurate predictions about which species would eventually go extinct”
Explanation: Paragraph F: Alroy says the overkill (hunting) model predicts which species die out → A.
22. Further grounded proof needed to explain humans’ indirect impact on mammals.
Answer: B (Ross D. E. MacPhee)
Key words: humans … but not directly … does not have empirical evidence for the hyperdisease hypothesis
Synonyms: indirect impact = not directly (disease); proof needed = lacks empirical evidence = “humans most likely brought about these extinctions … but not directly … MacPhee does not have empirical evidence”
Explanation: Paragraph E: MacPhee’s indirect (disease) theory still needs proof → B.
23. Over-hunting has caused the die-out of large mammals.
Answer: A (John Alroy)
Key words: even a very modest amount of hunting would have wiped these animals out
Synonyms: = “hunting-driven extinction is not only plausible, it was unavoidable … even a very modest amount of hunting would have wiped these animals out”
Explanation: Paragraphs B–C: Alroy argues hunting wiped out the large mammals → A.
24. Illness rather than hunting caused the extensive extinction.
Answer: B (Ross D. E. MacPhee)
Key words: people may have introduced hyperlethal disease
Synonyms: illness = disease = “he suggests that people may have introduced hyperlethal disease … which then spread wildly”
Explanation: Paragraph E: MacPhee attributes the extinctions to disease, not hunting → B.
25. Doubt raised through the study of several fossil records.
Answer: B (Ross D. E. MacPhee)
Key words: the relevant archaeological record contains barely a dozen examples of stone points embedded in mammoth bones
Synonyms: fossil records = archaeological record = “MacPhee … points out that the relevant archaeological record contains barely a dozen examples of stone points embedded in mammoth bones”
Explanation: Paragraph D: MacPhee uses the sparse fossil record to cast doubt on the hunting theory → B.
26. Climate shift is the main reason for extinction.
Answer: C (Russell W. Graham)
Key words: blame the loss on the weather … considerable climatic instability
Synonyms: climate shift = climatic instability = “its proponents blame the loss on the weather. The Pleistocene epoch witnessed considerable climatic instability, explains … Russell W. Graham”
Explanation: Paragraph F: Graham’s theory is that climate change caused the extinction → C.
Answer Key (Quick Reference)
| Q | Answer | Q | Answer |
|---|---|---|---|
| 14 | hunting | 21 | A |
| 15 | overkill model | 22 | B |
| 16 | disease (hyperdisease) | 23 | A |
| 17 | empirical evidence | 24 | B |
| 18 | climatic instability | 25 | B |
| 19 | geographical ranges | 26 | C |
| 20 | Younger Dryas event |
