AnarticlepublishedrecentlyinthescientificjournalNaturei...

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An article published recently in the scientific journal Nature is shedding new light on an important, but so far little has been appreciated, aspect of human evolution. In this article, Professors Dennis Bramble, and Daniel Lieberman suggest that the ability to run was a decisive factor in the development of our species. According to the two scientists, humans possess a number of anatomical（人體結構的）features that make them surprisingly good runners. “We are very confident that strong selection for running，which came at the expense of the historical ability to live in trees-was helpful in the origin of the modern human body form,” says Bramble, a biology professor at the University of Utah.

Traditional thinking up to now has been that the upright body form of modern humans has come about as a result of the ability to walk, and that running is simply a by-product of walking. Furthermore, humans have usually been regarded as poor runners compared to such animals as dogs, horses or antelopes. However, this is only true if we consider fast running over short distances. Even Olympic athlete can hardly run as fast as a horse can gallop, and can only keep up a top speed for fifteen seconds or so. Horses and antelopes, on the other hand, can run at top speed for several minutes, clearly outperforming us in this respect. But when it comes to long-distance running, humans do astonishingly well. They can maintain a steady pace for miles, and their overall speed compares favorably with that of horses or dogs.

Bramble and Lieberman examined twenty-six anatomical features found in humans. One of the most interesting of these is the nuchal ligament（頸背的韌帶）. When we run, it is this ligament that prevents our head from pitching back and forth or from side to side. Therefore, we are able to run with steady heads held high. The nuchal ligament is not found in any other surviving primates（靈長類動物）, although the fossil（化石）record shows that Homo erectus, an early human species that walked upright, much as we do, also had one. Then there are our Achilles tendons（跟腱）at the backs of our legs, which have nothing to do with walking. When we run, these tendons behave like springs, helping to push us forward. Furthermore, we have low, wide shoulders, virtually disconnected from our skulls (the bony part of the head), another anatomical adaptation which allows us to run more efficiently.

But what evolutionary advantage is gained from being good long-distance runners? One assumption is that this ability may have permitted early humans to obtain food more effectively. “What these features and fossil facts appear to be telling us is that running evolved in order for our direct ancestors to compete with other carnivores (animals that eat meat) for access to the protein needed to grow the big brains that we enjoy today.” says Lieberman.

can learn from the passage that the human ability to run _______.

A. was only recently described in a scientific journal

B. played an important part in human evolution

C. was considered more natural than the ability to live in trees

D. contributed to the form of human language

rding to the second paragraph, humans _______

A. are better runners than most other animals

B. are not good at running short distances

C. compare unfavorably with horses and dogs

D. are poor long-distance runners

appears that the nuchal ligament _______.

A. enables us to run with steady heads