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.
In considering possible explanations for this finding, the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples. 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.They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores ---in particular, 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 tothe 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.
第7题,答案D
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
我不懂的是A的解释，OG里说A是Support the researcher's conclusion.我没想通为什么。与本题相关的只有原文中粉色字体的部分。
而且OG还对本题解释说Lines 11–13（即原文粉色字体） state that demographic bias has been ruled out as anexplanation 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.请问OG是怎么就imply出来了这么个结论？？
我的理解：原文粉色字体是讲 researcher们排除了由于食肉动物分布而造成tooth fracture的这种解释，因为老的食肉动物在样本中比例是正常的——>推导出，样本中不能全是年轻样本，也需要有不同年龄层的，因为老年动物就是比青年的牙齿的损坏程度大（即OG解释中的this implies that older carnivores would be expected to have more tooth fractures than younger ones），加入了老年样本才可以称得上是一个比较合理的抽样。
我觉得自己这么解释的好牵强，望NN指点！！
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发表于 2012-1-9 13:23:08
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