在2014年6月21日的托福阅读考试中有这样一道题：部落迁徙。针对这道托福考题，出国留学网(www.liuxue86.com)小编来为大家普及一下关于部落迁徙的背景知识，这样有助于考生在面对这类题目时方便作答。小编在此提醒大家：历史题材文章结构为时间顺序，故而逻辑性较少，属于直线型文章。读文章时光看首句不一定能概括全段，需通过题目进行段意还原。而且还要多考虑各段之间的关系。
托福阅读真题再现：
版本一：讲某个部落的人迁徙到一个新的地方。他们即是游牧的，但又会种植作物。但是最后不得不迁徙，因为人太多了。wild animal和作物都不够吃。
版本二：climate对N族人的影响 他们开始更大范围的hunt 种grain之类的
版本三：
一个人种在younger dryra年代的生活 【编者注：此处人种经查找很可能为“Natufian”】
一开始说因为河流和水源渐渐干涸，猎物(game)也随之越来越少(此处有题)，所以人们需要更精湛的捕猎技巧，也因为这个发明了一种新的arrowhead(有题)。
后来呢他们捕不到足够的猎物了就settled了，开始cultivated rye crop， 把野生的rye慢慢“驯化”了。考古学家还在一个村子里发现了公元前11100-11020的rye，这是最早的人工培育rye。
但是呢，cultivated rye也不能满足需求啊，所以他们又变回游牧了，然后domestic rye又变wild了(有题)。
最后一段说他们后来因为水源干涸放弃了祖先生活的woodland，改而搬迁到更富饶的约旦河边(jordan river)。哦这里也有题。
解析：历史题材文章结构为时间顺序，故而逻辑性较少，属于直线型文章。读文章时光看首句不一定能概括全段，需通过题目进行段意还原。而且还要多考虑各段之间的关系。
相关背景：
Younger Dryas
From Wikipedia, the free encyclopedia
Three temperature proxies showing the Younger Dryas event at around 12 ka BP. The NGRIP sequence (red – mislabelled as GRIP) uses the water molecule isotopic composition – δ18O. The Vostok and EPICA Dome C series show delta-deuterium. All 3 proxies use the same vertical axis.
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief (1,300 ± 70 years) period of cold climatic conditions and drought which occurred between approximately 12,800 and 11,500 years BP. The Younger Dryas stadial is thought to have been caused by the collapse of the North American ice sheets, although rival theories have been proposed.
It followed the B?lling-Aller?d interstadial (warm period) at the end of the Pleistocene and preceded the preboreal of the early Holocene. It is named after an indicator genus, the alpine-tundra wildflower Dryas octopetala. In Ireland, the period has been known as the Nahanagan Stadial, while in the United Kingdom it has been called the Loch Lomond Stadial and most recently Greenland Stadial 1 (GS1). The Younger Dryas (GS1) is also a Blytt-Sernander climate period detected from layers in north European bog peat.
The Dryas stadials were cold periods which interrupted the warming trend since the Last Glacial Maximum 20,000 years ago. The Older Dryas occurred approximately 1,000 years before the Younger Dryas and lasted about 3000 years. The Oldest Dryas is dated between approximately 18,000 and 15,000 BP.
The Younger Dryas, an intense cooling and drying event of global proportions, has been attributed a major causal role in the adoption of agricultural economies in the southern Levant. Here, the impact of the Younger Dryas on human adaptations is evaluated using a small game index that measures the efficiency of human foraging as a proxy for site occupation intensity. The study examines faunal assemblages spanning the agricultural transition and dating to the Early and Late Natufian and Pre-Pottery Neolithic periods (ca. 14,500 to 11,000 Cal. BP). The small game index and other supporting evidence document major fluctuations in human site occupation intensity across this critical phase. Site occupation reached an unprecedented high during the Early Natufian, but quickly reverted to pre-Natufian levels with the onset of the Younger Dryas in the Late Natufian phase. By decreasing site occupation intensity and increasing mobility, the Late Natufians implemented effective demographic strategies to cope with changing resource distributions. In contrast, there is no evidence for intensified resource use or food stress in the Late Natufian, at least in comparison to the Early Natufian phase. Although, it is tempting to assign the Younger Dryas a causal role in the adoption of agricultural economies, support for this hypothesis (in the form of food stress and resource intensification) does not currently exist.
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