The Headland Hypothesis argues that foraging or non-agricultural tribes have been unable to collect adequate carbohydrate

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问题             The Headland Hypothesis argues that foraging or non-agricultural tribes
       have been unable to collect adequate carbohydrates in the rain forest due to its
       lack of starch producing species, and were thus forced to develop trade
Line     relationships with agriculturalists. This hypothesis has been shown to rest on
(5)      impossibly idealized conceptions of virgin rain forest, forager behavior and
       history, such that one may argue something diametrically different: millennia of
       trade relationships with agricultural peoples have led to changes in forager
       behaviors and in the composition of the forests they inhabit. Supposing that
       humans modify their environments in ways that are generally favorable toward
(10)     their continued survival, it follows that an increased reliance on agriculturalists
       for carbohydrates might lead to the gradual disappearance of rain forest
       starches. Horticulturalists are likely to dedicate the majority of their efforts
       toward staple starch crops such as rice or wheat, which in some environments
       may provide a more efficient source of carbohydrates than does foraging.
(15)     Foragers, then, would be inclined to assume the "professional primitive" role,
       and trade more tasty and nutritious rain forest resources such as meat and fruit
       in exchange for carbohydrates, as Headland himself observed in a multitude of
       cultures around the world.
           Foragers may have also lost some of their knowledge and technologies
(20)     related to carbohydrate extraction from the rain forest, and the carbohydrate-
       rich rain forest species may have arrested their co-evolution with foragers,
       leaving the impression that rain forests have always possessed insufficient
       quantities of such resources to support humans. A co-evolutionary argument is
       not, however, necessary to this line of reasoning, for rain forests may adapt
(25)     purely in terms of the quantity and availability of extant carbohydrate-rich
       species, as the case of sago palms evinces in two ways. Firstly, the selective
       harvesting of some trees has been shown to have a "thinning" effect which helps
       the species to gain sunlight and to thrive, positively affecting its long-term
       survival, reproduction and distribution at the expense of carbohydrate-rich
(30)     species. Secondly, the sago palm has two means of reproduction: vegetatively,
       or through "suckers", and through seed disbursal, which whether intentional
       and inadvertent is likely to increase when humans are harvesting the trees.
       Although sago palms are particularly prevalent in the areas where, for instance,
       the Penan foragers exploit it, there has been no study to show that this would
(35)     remain the case if the Penan were to move, or to cease exploiting the trees.
           Admittedly, this response to the Headland Hypothesis has problems, for
       not all carbohydrate producing species are disbursed by seeds, nor have they all
       been shown to benefit from human foraging behaviors. Theories of co-evolution
       do, however, predict that such relationships would be likely to evolve, and the
(40)     simple fact that disturbing the rain forest through fire, sago harvesting, and
       countless other means available to foragers can lead to better environments for
       carbohydrate growth, illustrates that significant changes could have occurred in
       much less time than one might expect.
According to the passage, the case of the Penan foragers’ cultivation of the sago palm fails to indicate that

选项 A、a co-evolutionary argument is unnecessary to establishing that rain-forest adaptation is the effect of human intervention
B、plant-species inimical to carbohydrate-rich species would continue to thrive without the practices of foraging peoples
C、the "thinning" effect produced by the Penan’s foraging practice is responsible for the sago palm’s long-term survival
D、the Penan have justification for abandoning the exploitation of sago palms or relocating to more carbohydrate-rich areas
E、rain forests may evolve as a result of the quantity and availability of extant carbohydrate-rich species

答案B

解析
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