Fossil footprints mistakenly attributed to bears were made by early humans

Fossil footprints mistakenly attributed to bears were made by early humans

Transcript¹

A new look at some fossilized footprints shows that more than one species of human was walking upright around 3.6 million years ago. (This story originally aired on ATC on Dec. 2, 2021.)

LEILA FADEL, HOST:

The earliest evidence of humans walking upright is the presence of fossilized footprints. They were left by someone walking through the mud nearly 3.7 million years ago. And it looks like that early human didn't walk alone. NPR's Nell Greenfieldboyce filed this report on researchers who took a new look at some other ancient tracks.

NELL GREENFIELDBOYCE, BYLINE²: Walking on two legs is a distinctively³ human thing to do. It seems to make us different than other living primates⁴.

ELLISON MCNUTT: It's a very strange way of kind of moving through the world.

GREENFIELDBOYCE: Ellison McNutt is a biological anthropologist⁵ at the Ohio University Heritage College of Osteopathic Medicine. She studies upright walking and says most four-legged creatures find it challenging.

MCNUTT: If you imagine asking your dog to do that, they're really wobbly. They're really uncomfortable. They don't want to do that.

GREENFIELDBOYCE: Yet humans did it early in their history. For example, at one site in Tanzania, a volcanic⁶ eruption⁷ over 3 1/2 million years ago covered the landscape with ash and preserved all kinds of tracks that had been left in the mud.

MCNUTT: So we're talking elephants and bunnies, birds. All kinds of things walked across this landscape, and they left these amazing footprints.

GREENFIELDBOYCE: Including one set of footprints that look quite human.

MCNUTT: And this trackway has been reconstructed to belong to a common and early human ancestor called Australopithecus afarensis, and this is the same species that the quite famous fossil Lucy belongs to.

GREENFIELDBOYCE: Now, when these were discovered back in the 1970s, workers also found a track of five footprints that looked more mysterious. Researchers speculated that these prints were created by a small bear walking upright.

MCNUTT: They were tentative about it and acknowledged that, you know, we don't have a good answer for this. This is a reasonable answer. Bears do stand up and walk upright.

GREENFIELDBOYCE: McNutt had actually been studying how bears do that when she came across a mention of these fossil tracks, which had been mostly forgotten for decades. She and her colleagues decided⁸ to reexamine them using modern technology. They did detailed⁹ comparisons to footprints left by humans, chimpanzees and young bears living at a sanctuary¹⁰.

MCNUTT: We ended up with four little juvenile¹¹ bears that we had stand up and walk through mud for either applesauce or maple¹² syrup¹³ as their reward at the end of it (laughter).

GREENFIELDBOYCE: Their results appear in the journal Nature. And it turns out the fossil footprints just aren't bearlike. Instead, there's signs of more humanlike features, such as a big toe. McNutt says it looks like there were two early human species walking around back then. In fact, they could have seen each other go by.

MCNUTT: The nature of fossil footprints and how these trackways are made is that they're in the same layer of mud. So these are likely made within the scale of hours to days from one another.

GREENFIELDBOYCE: All of this has convinced Stephanie Melillo. She's a paleoanthropologist at the Max Planck Institute for Evolutionary¹⁴ Anthropology¹⁵ in Germany.

STEPHANIE MELILLO: We see there the presence of two different kinds of hominid ancestors together in the same environment, in the same place, at the same time.

GREENFIELDBOYCE: She says one of the biggest questions about human evolution is why our ancestors started walking upright.

MELILLO: And I don't think that we really have a good answer to that question yet.

GREENFIELDBOYCE: But these footprints suggest that multiple human species coexisted while walking upright in different ways.

Nell Greenfieldboyce, NPR News.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

3 distinctively   

adv.特殊地，区别地

参考例句：

• "Public risks" is a recent term for distinctively high-tech hazards. “公共风险”是个特殊的高技术危害个人的一个最新术语。 来自英汉非文学 - 环境法 - 环境法
• His language was natural, unaffected, distinctively vivid, humorous and strongly charming. 语言既朴实无华，又鲜明生动，幽默而富有艺术魅力。

4 primates   

primate的复数

参考例句：

• Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
• Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。

5 anthropologist   

n.人类学家，人类学者

参考例句：

• The lecturer is an anthropologist.这位讲师是人类学家。
• The anthropologist unearthed the skull of an ancient human at the site.人类学家在这个遗址挖掘出那块古人类的颅骨。

6 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

7 eruption   

n.火山爆发；（战争等）爆发；（疾病等）发作

参考例句：

• The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
• The eruption of a volcano is spontaneous.火山的爆发是自发的。

8 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

9 detailed   

adj.详细的，详尽的，极注意细节的，完全的

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。

10 sanctuary   

n.圣所，圣堂，寺庙；禁猎区，保护区

参考例句：

• There was a sanctuary of political refugees behind the hospital.医院后面有一个政治难民的避难所。
• Most countries refuse to give sanctuary to people who hijack aeroplanes.大多数国家拒绝对劫机者提供庇护。

11 juvenile   

n.青少年，少年读物；adj.青少年的，幼稚的

参考例句：

• For a grown man he acted in a very juvenile manner.身为成年人，他的行为举止显得十分幼稚。
• Juvenile crime is increasing at a terrifying rate.青少年犯罪正在以惊人的速度增长。

12 maple   

n.槭树，枫树，槭木

参考例句：

• Maple sugar is made from the sap of maple trees.枫糖是由枫树的树液制成的。
• The maple leaves are tinge with autumn red.枫叶染上了秋天的红色。

13 syrup   

n.糖浆，糖水

参考例句：

• I skimmed the foam from the boiling syrup.我撇去了煮沸糖浆上的泡沫。
• Tinned fruit usually has a lot of syrup with it.罐头水果通常都有许多糖浆。

14 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。

15 anthropology   

n.人类学

参考例句：

• I believe he has started reading up anthropology.我相信他已开始深入研究人类学。
• Social anthropology is centrally concerned with the diversity of culture.社会人类学主要关于文化多样性。