美国英语听力80篇3 Lesson43

（单词翻译）

[00:06.24]For years, many scientists have considered walking on two legs as one sign of being human.
[00:15.46]Early humans were not thought to have used their knuckle¹ bones or other parts of their hands in walking.
[00:23.59]Now, however, American scientists have found evidence that humans developed from creatures that walked on their knuckles²,
[00:32.71]much like gorillas³ and chimpanzees do today.
[00:36.60]Researchers Brian Richmond and David Strait are from the George Washington University in Washington, D.C.
[00:45.84]They say they made their discovery almost by accident during a visit to the Smithsonian Institution in Washington.
[00:55.01]They compared old reports about the biology of apes with a copy of the wrist bone from Lucy,
[01:02.43]the most famous fossil remains⁴ of an early form of human.
[01:06.85]Their findings are reported in the publication Nature.
[01:11.37]The researchers examined how the wrist structure of chimpanzees and gorillas differs from other apes.
[01:20.01]They also examined the wrist bones from Lucy
[01:19.01]and another human-like creature that lived in Africa more than 3,000,000 years ago.
[01:26.56]The researchers say the ancient creatures had the same wrist structure as modern chimpanzees and gorillas.
[01:35.78]They found structures in the wrist bones that restricted the movement of the wrist.
[01:41.58]However; the researchers do not believe the creatures used their knuckles in walking
[01:48.32]because they had longer legs than the apes.
[01:51.80]The researchers say a creature with longer legs would have a difficult time
[01:58.28]supporting its weight on its lower legs and hands at the same time.
[02:04.05]They suggest that the wrist structure for knuckle-walking may have developed even earlier -- as much as 5,000,000 years ago.
[02:14.03]David Strait says the development of walking upright required major changes in the structure of the early human ancestors.