Argument 54 范文

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Argument 54/165
Arg 54species' extinctions caused by climate change

54) Humans arrived in the Kaliko Islands about 7,000 years ago, and within 3,000 years most of the large mammal species that had lived in the forests of the Kaliko Islands had become extinct. Yet humans cannot have been a factor in the species' extinctions, because there is no evidence that the humans had any significant contact with the mammals. Further, archaeologists have discovered numerous sites where the bones of fish had been discarded, but they found no such areas containing the bones of large mammals, so the humans cannot have hunted the mammals. Therefore, some climate change or other environmental factor must have caused the species' extinctions.

Write a response in which you examine the stated and/or unstated assumptions of the argument. Be sure to explain how the argument depends on these assumptions and what the implications are for the argument if the assumptions prove unwarranted.

165) Humans arrived in the Kaliko Islands about 7,000 years ago, and within 3,000 years most of the large mammal species that had lived in the forests of the Kaliko Islands were extinct. Previous archaeological findings have suggested that early humans generally relied on both fishing and hunting for food; since archaeologists have discovered numerous sites in the Kaliko Islands where the bones of fish were discarded, it is likely that the humans also hunted the mammals. Furthermore, researchers have uncovered simple tools, such as stone knives, that could be used for hunting. The only clear explanation is that humans caused the extinction of the various mammal species through excessive hunting.

Write a response in which you discuss one or more alternative explanations that could rival the proposed explanation and explain how your explanation(s) can plausibly account for the facts presented in the argument.




G1: Humans arrived in the Kaliko Islands about 7,000 years ago,

G2: and within 3,000 years most of the large mammal species that had lived in the forests of the Kaliko Islands had become extinct.

C1: Yet humans cannot have been a factor in the species' extinctions,

G3: because there is no evidence that the humans had any significant contact with the mammals.

G4: Further, archaeologists have discovered numerous sites where the bones of fish had been discarded, but they found no such areas containing the bones of large mammals,

C2: so the humans cannot have hunted the mammals.

C3: Therefore, some climate change or other environmental factor must have caused the species' extinctions.


A1(G3, C1): Human contact with the mammals must have left some traceable evidence.

A2(G4, C2): The absence of mammals bones implies that humans had not hunted the mammals.

A3(C3): Human activities did not affect the livelihood of the large mammals indirectly.


The author argues that cliamte changes and environmental factors instead of human activities are responsible for the extinctions of the large mammals. A number of assumptions have been made about the absence of evidence of contact between human and large mammals, the sites where fish bones were discarded and the climate changes. We need to examine these assumptions carefully to decide if the argument is reasonable.

To begin with, it is assumed that the absence of evidence for human-mammal contact means that there is no such contact. Since the possible contact would have occurred from 7000 years ago to 4000 years ago, many traces left for the contact might have simply disappeared over the long period of time. For example, humans could have set up traps to hunt and kill the mammals but after many years of geological movement and climate changes, it is not possible for archaeologists to find such traps. Some ancient humans could have been killed during their fight against the large mammals, but without the abilities or technologies to keep written records, their stories could not be passed to the present generations. In other words, we cannot assume there is no contact between humans and mammals simply because there is no evidence found yet.

The lack of bones of mammals in the site where fish bones were discarded could be interpreted in different ways. It cannot be assumed without further evidence that humans would discard the mammals' bones after killing and eating them. Maybe ancient humans had learned to make tools out of the bones. Or the bones had been used in certain religious ceremonies. And after being used as tools or for religious purposes, the bones could have been discarded in other places or buried somewhere that archaeologists nowadays had not yet discovered.

Another assumption being made here is that climate changes and other changes in environmental factors that may cause the extinctions are not related to human activities. Maybe the human settlement in the Islands was the main cause of the dramatic changes in the habitat and the ecosystem that would ultimately lead to the extinctions of the large mammals. If human activities have caused the climate or environmental changes, the arrival of humans would still be considered as a significant factor for the extinctions of large mammals even there was no significant contact between humans and large mammals.

In conclusion, a number of assumptions have been made in the argument. We need more evidence to examine the evidence. If these assumptions do not hold true, the argument would not stand.





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