（已解决）求助OG12的阅读第7题，有一点OG的解释不太明白

frankning007

原文：

A recent study has provided clues to predator prey dynamics in the late Pleistocene era. Researchers compared the number of tooth fractures in present-day carnivores with tooth fractures in carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Breatar

pits in Los Angeles. The breakagefrequencies in the extinct species were strikingly higher than those in the present-day species.（指出研究后的发现）

In considering possible explanations for this finding,（文章开始讨论对研究发现的解释）the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples. （排除了统计差异）They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits.（排除了保存差异）They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data.（排除了地域差异）The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores（给出解释：行为差异）—in particular（开始进一步阐述）, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.

题目（第7题）
The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that
(A) the older an individual carnivore is, the more likely it is to have a large number of tooth fractures
(B) the average age at death of a present-day carnivore is greater than was the average age at death of a Pleistocene carnivore
(C) in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as did younger individuals
(D) the methods used to determine animals’ ages in fossil samples tend to misidentify many older individuals as younger individuals
(E) data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores

答案：D

OG解释：

Begin by looking at the section on demographic bias. Lines 11–13 state that demographic bias has been ruled out as an explanation because“older individuals were not overrepresented in the fossil samples”. This implies that older carnivores would be expected to have more tooth fractures than younger ones. To answer this question, read each answer choice to find the one statement that undermines the researchers’ conclusion. If the method to determine age in the fossil samples is faulty and older carnivores are misidentified as younger ones, then demographic bias cannot be dismissed.

我的问题是：上述红色字体的结论是怎么推出来的？为什么older individuals没有占到过大的比例就说明他们会有更多的tooth fractures呢？在解释A选项时，为什么OG直接认为“This statement supports rather than undermines the researchers’ conclusion”呢？

谢谢！

铁铁

从常识上讲，越older， tooth fractures 越多。 老年人的牙口比不上年轻人啊。

所以在比较时，要除去older carnivores ，防止随着年龄而老化的因素对比较结果的影响

DavisLX

说下我的想法
researcher 排除demographic bias有他的目的所在的。。

那么也就暗示着 如果存在demographic bias，他们的conclusion就可能会不准确。

从这点入手，D 表示可能会有demographic bias 所以选D。

至于demographic bias的影响 楼上讲得很清楚了。
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关于A选项：researcher已经做了的事是排除了demographic bias，如果有新的调查表明，demographic bias会导致结果不准确（A选项所说的），那么其实这个调查其实显示了researcher是多么的正确 所以是支持的

frankning007

明白了，多谢楼上二位的解释！
关于A选项的这个，按我的逻辑理解起来有些绕，因此以后要多注意。
再次感谢！

flowers0820

可是这不是说 were not overrepresented嘛，那就是说，因为 没有占太多，没有太多older ，，，
跟楼上2位解释不一样锕。。

二楼说 要去掉older，，可是这里明明说 没有older。。。
三楼如果同二楼，也回答的很牵强了

shiki0426

不牽強...
從not overrepresented 就可以imply 若是overrepresented則年齡(因)與裂痕(果)關係成立
且
從上述可知
A的確重述了imply的部份 所以support

妞妞扭扭

q1weruqt

不牽強...
從not overrepresented 就可以imply 若是overrepresented則年齡(因)與裂痕(果)關係成立
且
從上述可知
A的確重述了imply的部份 所以support

-- by 会员 shiki0426 (2011/3/29 14:48:33)

这么理解也可以。我的理解是原文只说老的个体的数量，而未提及老的个体裂痕的数量，所以A中纠结老的个体的裂痕数量与原文无关。关键还是要抓住重点，原文的重点是老的个体，直接否认老的个体判断错了就可以了。

dolphinhot

我的解释：
首先原文是要找the breakage frequencies in the extinct species were strikingly higher...（lines8-10)的原因.如果A正确，越老的就有越多的tooth fractures(即 breakage),则我们可以推出older可能就是原因。随即就可以推出demograchic bias是原因。所以是strenghten而不是weaken。

dolphinhot

发现还没说完。接上面的。首先原文是要找the breakage frequencies in the extinct species were strikingly higher...（lines8-10)的原因.如果A正确，越老的就有越多的tooth fractures(即 breakage),则我们可以推出older可能就是原因。随即就可以推出demograchic bias是原因。但是，older individuals并没有在fossil samples中发现有overrepresent，就是说老年的不多，即不会有多的tooth fractures。所以demograchic bias并不是higher frequencies of breakage的原因。所以A是strenghten而不是weaken.(我认为这是一道逻辑的取非题）不知道这样讲请不清楚。