题目信息
Anthropologists once thought that the ancestors
of modern humans began to walk upright because
it freed their hands to use stone tools, which they
had begun to make as the species evolved a brain of
increased size and mental capacity. But discoveries
of the three-million-year-old fossilized remains of
our hominid ancestor Australopithecus have yielded
substantial anatomical evidence that upright walking
appeared prior to the dramatic enlargement of the
brain and the development of stone tools.
Walking on two legs in an upright posture (bipedal
locomotion) is a less efficient proposition than walking
on all fours (quadrupedal locomotion) because several
muscle groups that the quadruped uses for propulsion
must instead be adapted to provide the biped with
stability and control. The shape and configuration
of various bones must likewise be modified to allow
the muscles to perform these functions in upright
walking. Reconstruction of the pelvis (hipbones) and
femur (thighbone) of “Lucy,” a three-million-year-old
skeleton that is the most complete fossilized skeleton
from the Australopithecine era, has shown that they
are much more like the corresponding bones of the
modern human than like those of the most closely
related living primate, the quadrupedal chimpanzee.
Lucy's wide, shallow pelvis is actually better suited to
bipedal walking than is the rounder, bowl-like pelvis of
the modern human, which evolved to form the larger
birth canal needed to accommodate the head of a
large-brained human infant. By contrast, the head of
Lucy's baby could have been no larger than that of a
baby chimpanzee.
If the small-brained australopithecines were not
toolmakers, what evolutionary advantage did they
gain by walking upright? One theory is that bipedality
evolved in conjunction with the nuclear family:
monogamous parents cooperating to care for their
offspring. Walking upright permitted the father to
use his hands to gather food and carry it to his mate
from a distance, allowing the mother to devote more
time and energy to nurturing and protecting their
children. According to this view, the transition to
bipedal walking may have occurred as long as ten
million years ago, at the time of the earliest hominids,
making it a crucial initiating event in human evolution.
of modern humans began to walk upright because
it freed their hands to use stone tools, which they
had begun to make as the species evolved a brain of
increased size and mental capacity. But discoveries
of the three-million-year-old fossilized remains of
our hominid ancestor Australopithecus have yielded
substantial anatomical evidence that upright walking
appeared prior to the dramatic enlargement of the
brain and the development of stone tools.
Walking on two legs in an upright posture (bipedal
locomotion) is a less efficient proposition than walking
on all fours (quadrupedal locomotion) because several
muscle groups that the quadruped uses for propulsion
must instead be adapted to provide the biped with
stability and control. The shape and configuration
of various bones must likewise be modified to allow
the muscles to perform these functions in upright
walking. Reconstruction of the pelvis (hipbones) and
femur (thighbone) of “Lucy,” a three-million-year-old
skeleton that is the most complete fossilized skeleton
from the Australopithecine era, has shown that they
are much more like the corresponding bones of the
modern human than like those of the most closely
related living primate, the quadrupedal chimpanzee.
Lucy's wide, shallow pelvis is actually better suited to
bipedal walking than is the rounder, bowl-like pelvis of
the modern human, which evolved to form the larger
birth canal needed to accommodate the head of a
large-brained human infant. By contrast, the head of
Lucy's baby could have been no larger than that of a
baby chimpanzee.
If the small-brained australopithecines were not
toolmakers, what evolutionary advantage did they
gain by walking upright? One theory is that bipedality
evolved in conjunction with the nuclear family:
monogamous parents cooperating to care for their
offspring. Walking upright permitted the father to
use his hands to gather food and carry it to his mate
from a distance, allowing the mother to devote more
time and energy to nurturing and protecting their
children. According to this view, the transition to
bipedal walking may have occurred as long as ten
million years ago, at the time of the earliest hominids,
making it a crucial initiating event in human evolution.
The theory mentioned in lines 35–38 (marked with boldface)suggests that which of the following was true for the hominid ancestors of modern humans before they made the transition to walking upright?
A:Their brains were smaller than the brains of present-day chimpanzees.
B:They competed rather than cooperated in searching for food.
C:Their mating patterns and family structure were closer to those of present-day chimpanzees than to those of modern humans.
D:Males played a more significant role in child rearing than they played after the transition to walking upright.
E:Females' ability to nurture and protect their offspring was limited by the need to find food for themselves.
参考答案及共享解析
共享解析来源为网络权威资源、GMAT高分考生等； 如有疑问，欢迎在评论区提问与讨论
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已选答案：
正确答案：
E:Females' ability to nurture and protect their offspring was limited by the need to find food for themselves.
答案 E
第35-38行中提到的理论认为，现代人类的祖先进化出了两足行走的能力，这主要是因为它赋予了一夫一妻制的夫妇合作照顾后代的能力。根据这个理论，因为他们现在可以直立行走，父亲们可以用他们的手收集食物，并从远处把食物带给他们的配偶。这反过来又使母亲花费更多的时间和精力来养育和保护她们的孩子。这意味着，在直立行走之前，母亲必须花更多的时间获取自己的食物，因此较少的时间来养育和保护她们的后代。
A.文中提到南方古猿婴儿的大脑并不比黑猩猩婴儿的大。这并不意味着这些祖先的大脑比黑猩猩的小。文章中没有任何东西表明这个理论与此不一致。
B.该理论认为，直立行走使一夫一妻制的夫妇能够合作获取食物;简单的缺乏合作并不意味着这些祖先一定要争夺食物。例如，这些群体可能参与了合作狩猎，就像现在许多非两足动物一样。
C.该理论确实表明，在两足动物发展之前，这些祖先没有能力合作照顾。然而，这并不意味着它们的交配模式和家庭结构更接近黑猩猩，而不是现代人类。
D.这个理论实际上提出了相反的观点:两足行走能力的发展是因为它使古人类父母之间有了更多的合作照顾。
E.正确选项。如上所述，直立行走能力的发展使得父亲能够帮助母亲获取食物。这就为母亲们腾出了时间和精力来养育和保护她们的后代。
第35-38行中提到的理论认为，现代人类的祖先进化出了两足行走的能力，这主要是因为它赋予了一夫一妻制的夫妇合作照顾后代的能力。根据这个理论，因为他们现在可以直立行走，父亲们可以用他们的手收集食物，并从远处把食物带给他们的配偶。这反过来又使母亲花费更多的时间和精力来养育和保护她们的孩子。这意味着，在直立行走之前，母亲必须花更多的时间获取自己的食物，因此较少的时间来养育和保护她们的后代。
A.文中提到南方古猿婴儿的大脑并不比黑猩猩婴儿的大。这并不意味着这些祖先的大脑比黑猩猩的小。文章中没有任何东西表明这个理论与此不一致。
B.该理论认为，直立行走使一夫一妻制的夫妇能够合作获取食物;简单的缺乏合作并不意味着这些祖先一定要争夺食物。例如，这些群体可能参与了合作狩猎，就像现在许多非两足动物一样。
C.该理论确实表明，在两足动物发展之前，这些祖先没有能力合作照顾。然而，这并不意味着它们的交配模式和家庭结构更接近黑猩猩，而不是现代人类。
D.这个理论实际上提出了相反的观点:两足行走能力的发展是因为它使古人类父母之间有了更多的合作照顾。
E.正确选项。如上所述，直立行走能力的发展使得父亲能够帮助母亲获取食物。这就为母亲们腾出了时间和精力来养育和保护她们的后代。
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