「Question No. 51」
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.
First of all, since humans may have done activities that deprived the mammals of their food or reduce the food supply or that destroyed the mammals’ habitats, ← 句型技法：用原因状语从句引出对于“它因”的陈述。humans’ significant contact with the mammals may not be the cause of the mammals’ extinction as the author suggests. For example, humans may have cut down trees, which may have been the mammals’ source of food, ← 用定语从句建立人类活动对于哺乳动物食物源的影响。and meanwhile built housing on the grasslands, which may have been the mammals’ habitats ← 用定语从句建立人类活动对于哺乳动物栖息地的影响。. As a result, the mammals had become extinct because of the loss of food supply and habitats.
逻辑点思路2（常见逻辑疑点：偷换概念：打猎等同于产生丢弃的骨头 / 它因问题：没有丢弃的骨头的原因不一定是没有狩猎。）：
The author also assumes that hunting would have surely produced discarded bones and that, otherwise, no hunting would have taken place. ← 写作步骤：上来就直接说明作者的assumption是什么。However, it is likely that the reason of that no large mammals’ bones had been found is mammals’ bones had been made to be tools and ornaments.← 写作步骤：然后分析作者assumption的错误。如果理解为它因问题，那么就在此举出典型的/在常识上最有可能的其它原因。For example, the large ones may have been made weapons and the small ones may have been made jewelries.← 写作步骤：就着上一步的分析进一步展开，比如举例进一步诠释。Therefore, although there are no discarded mammals’ bones, humans may still have hunted the mammals. ← 写作步骤：得出关于这一个逻辑疑点的小总结。