VOA慢速英语2021--早期人类祖先直立行走的新证据

New Evidence Found of Early Human Ancestors Walking Upright

Scientists are taking a second look at footprints made in ash from a volcano millions of years ago in modern-day Tanzania.

The footprints were first found in the 1970s. Scientists started taking another look at them in 2019. They were surprised to discover that the footprints in the ash were made by two different species.

Two sets of tracks were discovered in 1976 and 1978. At the time, scientists believed they were left by a human ancestor and another creature, like a bear. However, now the scientists believe the footprints may have been made by two different species of human ancestors.

Ellie McNutt of Ohio University is the lead writer of the study published in Nature. McNutt noted¹ the tracks are the first evidence of walking on two feet in the human fossil record.

Jeremy DeSilva of Dartmouth College co-wrote the study. DeSilva said the footprints show there were different ways of walking upright at that time. That is because the set of footprints discovered in 1978, also from the area, show a different way of walking. The footprints found in 1978 have been linked with the human ancestor known as Australopithecus afarensis. That is the family of early humans that ‘Lucy' belongs to. Lucy is a famous group of bones found in Ethiopia in 1974.

Years ago, scientists did not think the footsteps found in 1976 were connected to humans because one foot crossed over the other as the being walked. This is called "cross-stepping," DeSilva said. He called it "peculiar²."

The scientists believe the being which made the newly found steps was about one meter tall. But they can only guess about other qualities it might have had.

DeSilva said it is possible the steps were taken by an unknown human ancestor or it could have been one already known.

Scientists say the ancestors of modern humans separated from chimpanzees between 6 and 7 million years ago. Walking on two feet was an important evolutionary³ step. So, scientists are excited by the new finding.

Changes in the bones of the hips⁴, spine⁵, feet and legs permitted human ancestors to walk upright. This happened millions of years before modern human beings, known as homo sapiens, appeared 300,000 years ago.

Scientists think the changes might have happened so that early humans could better see dangerous animals in the African grasslands⁶.

Words in This Story

ash – n. the remains⁷ of something that has been burned up

species – n. a group of animals or plants that are similar and can produce young animals or plants

tracks – n. (pl.) a mark left on the ground by a moving animal, person, or vehicle — usually plural⁸

fossil – n. something (such as a leaf, bones, or a footprint) that is from a plant or animal which lived in ancient times and that has become mineralized into rock

footprint – n. the mark left by someone's foot or shoe

peculiar – adj. not usual or normal

evolution – n. a theory that the differences between modern plants and animals are because of changes that happened by a natural process over a very long time

1 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

2 peculiar   

adj.古怪的，异常的；特殊的，特有的

参考例句：

• He walks in a peculiar fashion.他走路的样子很奇特。
• He looked at me with a very peculiar expression.他用一种很奇怪的表情看着我。

3 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

4 hips   

abbr.high impact polystyrene 高冲击强度聚苯乙烯，耐冲性聚苯乙烯n.臀部( hip的名词复数 )；[建筑学]屋脊；臀围（尺寸）；臀部…的

参考例句：

• She stood with her hands on her hips. 她双手叉腰站着。
• They wiggled their hips to the sound of pop music. 他们随着流行音乐的声音摇晃着臀部。 来自《简明英汉词典》

5 spine   

n.脊柱，脊椎；(动植物的)刺；书脊

参考例句：

• He broke his spine in a fall from a horse.他从马上跌下摔断了脊梁骨。
• His spine developed a slight curve.他的脊柱有点弯曲。

6 grasslands   

n.草原，牧场( grassland的名词复数 )

参考例句：

• Songs were heard ringing loud and clear over the grasslands. 草原上扬起清亮激越的歌声。 来自《现代汉英综合大词典》
• Grasslands have been broken and planted to wheat. 草原已经开垦出来，种上了小麦。 来自《简明英汉词典》

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 plural   

n.复数；复数形式；adj.复数的

参考例句：

• Most plural nouns in English end in's '.英语的复数名词多以s结尾。
• Here you should use plural pronoun.这里你应该用复数代词。