Scientists have solved the mystery of why the overwhelming majority of mammoth fossils (化石) are male.
Much like wild elephants today, young male Ice Age mammoths probably travelled around alone and more often got themselves into risky situations where they were swept into rivers, or fell through ice or into mud, lakes or sinkholes that preserved their bones for thousands of years, scientists say.
Females, on the other hand, travelled in groups led by an older matriarch who knew the landscape and directed her group away from danger.
“Without the benefit of living in a herd led by an experienced female, male mammoths had a much higher risk of dying in natural traps such as mud holes, rock cracks and lakes，”said coauthor Love Dalen of the Swedish Museum of Natural History in a report published on Thursday in the journal Current Biology.
The study used genetic data to determine the sex of 98 woolly mammoth fossils in Siberia Researchers found that 69% of the samples were male, a heavily unbalanced sex ratio, assuming that the sexes were fairly even at birth.
“We were very surprised because there was no reason to expect a sex bias in the fossil record，” said first author Patricia Pecnerova, also of the Swedish Museum of Natural History. Therefore, researchers believe that something about the way they lived influenced the way they died.Most bones, tusks, and teeth from mammoths and other Ice Age animals haven't survived, explained Dalen.
“It is highly likely that the remains that are found in Siberia these days have been preserved because they have been buried, and thus protected from weathering.”
These giant, tusked plant eaters disappeared about 4,000 years ago. While there is no scientific agreement about the causes of their disappearance from the planet, most believe that climate change, excessive hunting by humans and the spread of other animals into mammoth feeding grounds were influential factors.
本文是一篇说明文。介绍了科学家们做了一项研究调查，揭开了mammoth化石大部分是雄性的原因，并且还指出mammoth灭绝的可能性原因。
1．The underlined word “matriarch” in paragraph 3 means ________.
A．figure head B．female leader
C．experienced animal D．mature mammoth
答案：B
解析：词义猜测题。根据第三段可知，雌性动物成群迁徙，肯定是在年老的“雌性领队”的带领下迁徙的，这头“领队动物”对环境更了解，能带领团队避开危险。故选B。
2．Why do the majority of mammoth fossils come from male animals?
A．Scientists find it easier to study male fossilized bones.
B．There were more male mammoths in comparison to females.
C．Male mammoths were better able to adapt to the changing circumstances.
D．Male mammoths more frequently died in places where fossils could form.
答案：D
解析：推理判断题。题干问的是为什么大多数的mammoth化石都是雄性的。根据第二段可知雄性常常单独行动，因此使自己陷入困境而丧失生命，它们死的地方常常能够形成化石。故选D。
3．Which of the following is suggested as a reason for mammoths dying out?
A．The increasing competition for food.
B．The cooling of the earth's temperature.
C．The disappearance of male mammoths.
D．The risky behaviour of younger mammoths.
答案：A
解析：推理判断题。题干问的是下列哪一项是文章暗示出的这种动物灭绝的一种原因。根据最后一段 While there is no scientific agreement about the causes of their disappearance from the planet, most believe that climate change, excessive hunting by humans and the spread of other animals into mammoth feeding grounds were influential factors可知，其他动物蔓延到mammoth的觅食地，即抢走mammoth的食物也是这种动物从地球上消失的一个因素；也就是说，对食物竞争的日益激烈是其灭绝的一种原因。故选A。
4．What is the text type of the passage?
A．A newspaper article. B．An academic essay.
C．A historical description. D．A science fiction story.
答案：A
解析：推理判断题。题干问的是本篇文章的语篇类型是什么。根据第一段 Scientists have solved the mystery of...和第五段 The study used genetic data to determine...以及最后一段可以看出，该文揭示了mammoth化石大部分是雄性的原因，所以这是刊登在报纸上的一篇文章。故选A。
