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Scientists are taking a second look at footprints made in ash from a volcano millions of years ago in modern-day Tanzania.
科学家们再次对数百万年前在今天的坦桑尼亚的一座火山的火山灰中留下的脚印进行研究。
The footprints were first found in the 1970s.
这些脚印最早是在20世纪70年代被发现的。
Scientists started taking another look at them in 2019.
科学家们在2019年再次开始对它们进行研究。
They were surprised to discover that the footprints in the ash were made by two different species.
他们惊讶地发现，火山灰中的脚印是由两个不同的物种留下的。
Two sets of tracks were discovered in 1976 and 1978.
这两组脚印是在1976年和1978年被发现的。
At the time, scientists believed they were left by a human ancestor and another creature, like a bear.
当时，科学家们认为它们是由人类祖先和另一种生物（比如熊）留下的。
However, now the scientists believe the footprints may have been made by two different species of human ancestors.
然而，现在科学家们认为这些脚印可能是由两个不同物种的人类祖先留下的。
Ellie McNutt of Ohio University is the lead writer of the study published in Nature.
俄亥俄大学的埃莉·麦克纳特是发表在《自然》（Nature）期刊上的这项研究的主要作者。
McNutt noted the tracks are the first evidence of walking on two feet in the human fossil record.
麦克纳特指出，这些脚印是人类化石记录中第一个用两只脚行走的证据。
Jeremy DeSilva of Dartmouth College co-wrote the study.
达特茅斯学院的杰里米·德席尔瓦共同撰写了这项研究。
DeSilva said the footprints show there were different ways of walking upright at that time.
德席尔瓦说，这些脚印表明当时有不同的直立行走方式。
That is because the set of footprints discovered in 1978, also from the area, show a different way of walking.
这是因为在1978年发现的同样来自该地区的那组脚印显示了一种不同的行走方式。
The footprints found in 1978 have been linked with the human ancestor known as Australopithecus afarensis.
在1978年发现的脚印与人类祖先阿法南方古猿有关。
That is the family of early humans that 'Lucy' belongs to.
这就是“露西”所属的早期人类家族。
Lucy is a famous group of bones found in Ethiopia in 1974.
露西是于1974年在埃塞俄比亚发现的一组著名的骨骼。
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.
多年前，科学家们认为在1976年发现的脚印与人类无关，因为这组脚印的“主人”是一只脚交叉在另一只脚前行走的。
This is called "cross-stepping," DeSilva said. He called it "peculiar."
德席尔瓦说，这就是所谓的“交叉步”。他称这很“奇特”。
The scientists believe the being which made the newly found steps was about one meter tall.
科学家们认为，留下这些新发现的脚印的生物大约有一米高。
But they can only guess about other qualities it might have had.
但他们只能推测出它可能具有的其他特性。
DeSilva said it is possible the steps were taken by an unknown human ancestor or it could have been one already known.
德席尔瓦说，这些脚印可能是由未知的或已知的人类祖先留下的。
Scientists say the ancestors of modern humans separated from chimpanzees between 6 and 7 million years ago.
科学家们说，现代人的祖先在600万到700万年前从黑猩猩中分离出来。
Walking on two feet was an important evolutionary step.
用两只脚行走是进化的重要一步。
So, scientists are excited by the new finding.
因此，科学家们对这一新发现感到兴奋。
Changes in the bones of the hips, spine, feet and legs permitted human ancestors to walk upright.
臀部、脊椎、脚和腿部骨骼的变化使人类祖先能够直立行走。
This happened millions of years before modern human beings, known as homo sapiens, appeared 300,000 years ago.
这发生在30万年前现代人类（即智人）出现之前的数百万年。
Scientists think the changes might have happened so that early humans could better see dangerous animals in the African grasslands.
科学家们认为，这些变化的发生可能是为了让早期人类能够更好地看到非洲草原上的危险动物。
I'm Dan Friedell.
丹·弗里德尔为您播报。
译文为可可英语翻译，未经授权请勿转载！
