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Study: Fossil Bones Add to Evidence about Earliest Ancestor

时间:2022-10-05 22:59:14

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Study: Fossil Bones Add to Evidence about Earliest Ancestor

Researchers say new examinations of arm and leg fossils support existing evidence that an identified species could be our earliest known ancestor.

The fossil bones were found near a skull1 that was discovered in 2001 in the African nation of Chad. The scientists who found the skull have suggested that it belonged to a being who walked upright and could be our earliest known ancestor.

Now, researchers say a study involving the arm and leg fossils strengthens that argument. The team looked for signs that the species walked on two feet instead of four. The move toward upright walking is a main division between human and ape development.

The fossil species, called Sahelanthropus tchadensis, walked upright while still being able to climb and move around in trees, the team said.

The species dates back to around seven million years ago, which makes it by far the oldest known human ancestor. That is about a million years older than other early known hominins. Hominin is a group that includes modern humans and species closely related to humans.

Researchers – including scientists at the University of Poitiers in France – closely examined the fossil skull, teeth and jaw2. They argued that the animal must have walked on two feet and held its head upright. This argument was based on the placement of a hole in the skull where the spinal3 cord connects to the brain.

Other experts, however, have not been persuaded, or convinced, by the early evidence.

The latest work includes a thigh4 bone that was not linked to S. tchadensis at first and went unstudied for years. Other researchers at the French university found the bone in the laboratory's collection and realized it probably belonged to the fossil species.

Compared to bones from other species, the thigh was linked closer to upright-walking humans than apes who used their feet and arms, the study found. The new findings were recently reported in the publication Nature.

Study co-writer Franck Guy recently spoke5 about the fossil examinations to reporters. "There is not one feature. There is just a total pattern of features," he said.

The debate over the species is likely to continue. Ashley Hammond is a scientist at the American Museum of Natural History in New York. She said more research is needed to find the being's rightful place on the evolutionary6 tree.

"I'm not fully7 convinced yet," Hammond told The Associated Press. "This could still also be a fossil ape."

Another researcher at the University of Poitiers, Roberto Macchiarelli, examined the thigh bone in the past and decided8 the species was probably an ape. Looking at the new study, Macchiarelli said he still does not believe the species was a hominin, though it might have walked on two legs at times.

Rick Potts is with the Smithsonian's National Museum of Natural History and directs the organization's Human Origins Program. He said the thigh bone puts the species on "better footing" as a possible early human ancestor. But he added that the real confirmation9 will come down to a common saying in the field: "Show me more fossils."

Words in This Story

fossil – n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks

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

feature – n. a typical quality or important part of something

pattern – n. a regular and repeated way in which something happens

evolution – n. a gradual process of change and development


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1 skull CETyO     
n.头骨;颅骨
参考例句:
  • The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
  • He fell out of the window and cracked his skull.他从窗子摔了出去,跌裂了颅骨。
2 jaw 5xgy9     
n.颚,颌,说教,流言蜚语;v.喋喋不休,教训
参考例句:
  • He delivered a right hook to his opponent's jaw.他给了对方下巴一记右钩拳。
  • A strong square jaw is a sign of firm character.强健的方下巴是刚毅性格的标志。
3 spinal KFczS     
adj.针的,尖刺的,尖刺状突起的;adj.脊骨的,脊髓的
参考例句:
  • After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天,就已经使脊椎骨变得富有弹性了。
  • Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。
4 thigh RItzO     
n.大腿;股骨
参考例句:
  • He is suffering from a strained thigh muscle.他的大腿肌肉拉伤了,疼得很。
  • The thigh bone is connected to the hip bone.股骨连着髋骨。
5 spoke XryyC     
n.(车轮的)辐条;轮辐;破坏某人的计划;阻挠某人的行动 v.讲,谈(speak的过去式);说;演说;从某种观点来说
参考例句:
  • They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
  • The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。
6 evolutionary Ctqz7m     
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。
7 fully Gfuzd     
adv.完全地,全部地,彻底地;充分地
参考例句:
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
8 decided lvqzZd     
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 confirmation ZYMya     
n.证实,确认,批准
参考例句:
  • We are waiting for confirmation of the news.我们正在等待证实那个消息。
  • We need confirmation in writing before we can send your order out.给你们发送订购的货物之前,我们需要书面确认。

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