READING PASSAGE 1
You should spend about 20 minutes on Questions 1-13 which
are based on Reading
Passage 2 below.
Mammoth kill 2
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 Pliocene epoch from around 5 million
years ago, into the Holocene
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 4 m at the shoulder and
weighs up to 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 1 to 6 inches per year. Based on studies of their
close relatives, the modern
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 bulls
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-sized 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,
but it was only 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 they’re 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
ranges – the giant Jefferson’s
ground sloth, for example, lived as far north as the Yukon
and as far south as Mexico –
which 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 hyper lethal
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 hyper
disease could thus quickly
drive them to the point of no return. So far MacPhee does
not have empirical evidence
for the hyper disease hypotheses, and it won’t be easy to
come by hyper lethal 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 water. The
Pleistocene epoch witnessed considerable climatic
instability, explains palaeontologist
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 event
– pushed 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 gross – but believable.”
Questions 1-7
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 1-7 on your answer
sheet.
The reason why dad big size mammals become extinct 11,000
years ago is under hot
debate. The first explanation is that 1……………………….. of
human-made it happen. This
so-called 2………………………. began from the 1960s suggested
by an expert, who however
received criticism of lack of further information. Another
assumption promoted by
MacPhee is that deadly 3…………………….. from human causes
their demises. However,
his hypothesis required more 4…………………….. to testify
its validity. Graham proposed a
third hypothesis that 5…………………….. in Pleistocene
epoch drove some species
disappear, reduced 6……………………… posed a dangerous
signal to these giants,
and 7………………………. finally wiped them out.
Question 8-13
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
8 Human hunting well explained which species would
finally disappear.
9 Further grounded proof needed to explain human’s
indirect impact on mammals.
10 Overhunting situation has caused die-out of large
mammals.
11 Illness rather than hunting caused extensive
extinction.
12 Double raised through the study of several fossil
records.
13 Climate shift is the main reason for extinction.
READING PASSAGE 1: Mammoth Kill
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 Pliocene epoch from around 5 million years ago into the Holocene 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.
Paragraph A
Like their modern relatives, mammoths were quite large. The largest known species reached heights in the region of 4 m at the shoulder and weighed up to 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 1 to 6 inches per year. Based on studies of their close relatives, the modern 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 bulls lived solitary lives or formed loose groups after sexual maturity.
Paragraph 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-sized 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 but unavoidable. He has determined, using a computer simulation, that even a very modest amount of hunting would have wiped these animals out.
Paragraph 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.
Paragraph 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 ranges – the giant Jefferson’s ground sloth, for example, lived as far north as the Yukon and as far south as Mexico – which would have made slaughtering them in numbers sufficient to cause their extinction rather implausible, he says.
Paragraph 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 naïve 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.
Paragraph 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 water. The Pleistocene epoch witnessed considerable climatic instability, explains palaeontologist 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 event – pushed 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 gross – but believable.”
Answers and Explanations
Questions 1-7 (Summary Completion)
-
Arrival of humans
Location: Paragraph B
Explanation: It is stated that the demise of large mammals coincided with the arrival of humans in the New World. -
Overkill model
Location: Paragraph B
Explanation: The term "overkill model" is introduced in Paragraph B as the theory proposed by Paul S. Martin in the 1960s. -
Deadly disease
Location: Paragraph E
Explanation: MacPhee suggests that deadly diseases introduced by humans could have caused the extinctions. -
Empirical evidence
Location: Paragraph E
Explanation: MacPhee acknowledges the lack of empirical evidence to support the hyperdisease hypothesis. -
Climate change
Location: Paragraph F
Explanation: Graham argues that climatic instability during the Pleistocene epoch caused habitat changes, leading to extinction. -
Geographical ranges
Location: Paragraph F
Explanation: Graham mentions that shrinking geographical ranges posed a significant challenge to large mammals. -
Younger Dryas event
Location: Paragraph F
Explanation: Graham highlights the Younger Dryas event as the final major fluctuation that pushed species over the edge.
Questions 8-13 (Matching Opinions/Deeds)
-
A (John Alroy)
Location: Paragraph F
Explanation: Alroy claims the overkill model can accurately predict which species would eventually go extinct. -
B (Ross D. E. MacPhee)
Location: Paragraph E
Explanation: MacPhee believes more empirical evidence is needed to support the hyperdisease hypothesis. -
A (John Alroy)
Location: Paragraph B
Explanation: Alroy's computer simulations show that even modest hunting could have caused the extinction of large mammals. -
B (Ross D. E. MacPhee)
Location: Paragraph E
Explanation: MacPhee suggests that disease, rather than hunting, caused the extinction of large mammals. -
B (Ross D. E. MacPhee)
Location: Paragraph D
Explanation: MacPhee highlights the lack of fossil evidence, such as stone points in mammoth bones, to support the overkill hypothesis. -
C (Russell W. Graham)
Location: Paragraph F
Explanation: Graham attributes the extinction to climate change during the Pleistocene epoch.
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