单选题 Hominids started walking on two legs six million years ago, shortly after diverging from chimpanzees, according to a study of the inner structure of a fossilised thighbone. The finding puts upright posture at the base of the human family tree.
The evolution of upright posture is a key issue in anthropology. Together with large brain size, it marks the dividing line between humans and the great apes.
Researchers know that upright posture evolved first because the skeleton of famed Australopithecine，Lucy, has a small braincase but modem ankles. Yet with few known fossils older than about four million years, the details of how and when upright posture evolved have been hazy. Over the past few years, however, two important new finds have begun to fill in the gaps.
The older animal is Sahelanthropus tchadensis, which lived in Chad six to seven million years ago, but only its hominid cranium was found. More complete is the chimpanzee-sized Orrorin tugenensis, as 20 fossils from at least five individuals have been found in Kenya. These are about six million years old.
A team led by Brigitte Senut of the French Museum of Natural History in Paris initially classed Orrorin as a hominid, on the human side of the split from chimpanzees. This classification was based on skeletal features, but other anthropologists remained sceptical.
To address those doubts, Robert Eckhardt of Pennsylvania State University in the US carried out a CT scan on the most complete of Orrorin's three thighbones. He hoped that revealing its internal structure would indicate the biomechanical use of the bone.
The critical part of each thighbone—which consists of a strong outer cortex and a spongy core—is the neck shaft that connects the top part of bone with the hip joint. Essentially, the thighbones are supporting a horizontal pelvic beam that takes the weight of the head and body. The precise load this places on the thighbones depends on body posture, and this determines the musculature and structure of the thighbones.
In knuckle-walking chimps, the cortex is the same thickness on the top and bottom of the bone. However, bipedal, upright walking applies different forces, which means the codex in humans is at least four times thicker on the bottom part of the bone.
Fossilisation usually obscures the internal structures of bones, so " there aren't many hominids in which scanning will work " , Eckhardt told New Scientist.
However, with Orrorin he was lucky. He and a research group including Senut found that the lower part of the thighbone in Orrorin is three times thicker than the upper—making its walking habits much closer to humans than chimps.

单选题 Which of the following is true about Lucy?

【正确答案】 D

【答案解析】[解析] 细节题。由关键词Lucy可定位到第三段首句。由该句中的first可以看出，研究人员是通过研究Lucy才知道直立行走是首先进化成的，故D项正确。A项是对文中的生词“famed Australopithecine”进行字面上的改编，由上下文可以看出，Lucy是原始人或猿，不可能是人类学家。Australopithecine指的是一种在非洲发现的类人猿。B项是对文中modem ankles的生搬硬套，文中是说Lucy的脚踝骨与现代人类很像，并不是说其为现代时尚疯狂。C项表述过于绝对，文中提到她“has a small braincase”，也就是说她的大脑还没有进化到人类的程度。

单选题 Which of the following words can substitute for " hazy " (Sentence 2, Para. 3)?

【正确答案】 B

【答案解析】[解析] 词汇题。第三段第二句提到，400万年以前的化石很少，所以人类如何以及何时直立行走的细节是“hazy”。可以看出，作者前面谈的是证据不足，后面就应该是细节情况不清楚或不知道之类的话。B项obscure意为“模糊的，不清楚的”，符合文义。A项意为“被发现的”，显然逻辑上说不通。C项意为“被忽视的”：可供研究的证据少与主观上忽视事物细节并无必然联系。D项意为“推断出”，与文意不符。

单选题 Which of the following is true according to the 7th and 8th paragraph?

【正确答案】 C

【答案解析】[解析] 细节题。根据题干可定位到第七、八两段。由第七段末句可知，骨盆承受头部和身体的重量，而大腿支持骨盆，大腿所承受的骨盆给它的确切负荷取决于人的姿势。也就是说姿势决定大腿需要承受的重量。故C项正确。A项是对第七段首句中“is the neck shaft that connects the top part of bone with the hip joint”的误解，这里neck指的是股骨与髋关节的连接处，而不是指人的颈部。第七段首句中的插入语“which consists of a strong outer cortex and a spongy core”修饰的是“each thighbone”，并不是关键部位，故排除B。在第八段第二句中，bipedal和upright共同修饰walking，指的是双脚直立行走这种姿势。different是相对于前面的knuckle-walking而说的，并不是说“bipedal walking”和“upright walking”不同；故排除D。

单选题 In the sentence " this determines the musculature and… " (Para 7), " this " refers to_______.

【正确答案】 A

【答案解析】[解析] 指代关系题。根据题干可定位到第七段。由第七段末句可知，骨盆施加在股骨上的确切负荷由身体姿势决定，同时这个负荷又决定了股骨的肌肉组织和结构。故A项“确切负荷”正确。这里是要说明影响大腿肌肉和骨骼结构的原因，不可能是股骨自己决定自己的肌肉和骨骼，故排除B。C项是强干扰项。本句的基本逻辑如下：body posture决定precise load，而precise load(即问题中的this)决定股骨的结构，可见body posture并不直接对股骨结构产生影响，故排除C。“The precise load this places on the thighbones”中的“this”指的是骨盆，这与题干中的“this”不是一回事，由此排除D。

单选题 The best title for the passage might be_______.

【正确答案】 D

【答案解析】[解析] 主旨题。文章开篇就提到，近期的科学发现表明，原始人类是在大约6百万年之前开始直立行走的，然后通过分析这个科学发现来说明人类是在何时开始直立行走的。可见，整篇文章都是围绕人类祖先开始直立行走这个主题展开的，故D项正确。作者重点论述的是人类开始直立行走的时间，而不是对原始人类与黑猩猩的比较，故排除A。B项仅是文中的细枝末节，并非作者的意图所在，故排除。文章多处提到了股骨结构，但其目的在于通过对股骨结构的分析和研究来证明原始人类是在何时开始直立行走的，并非文章主旨，故排除C。