VOA慢速英语--在墨西哥发现的工具表明人类更早到达北美

Stone tools found in a Mexican cave suggest people were living in North America as early as 26,500 years ago, much earlier than past research has shown.

Scientists recently reported they had found 1,930 limestone¹ tools in a mountain cave in Mexico's north-central Zacatecas state. The discovery included small flakes² and fine blades that may have been used for cutting meat. Small points were also found that could have been used as spear tips for hunting.

Ciprian Ardelean is an archeologist at the Autonomous³ University of Zacatecas. He is the lead writer of a study on the findings that appeared in the publication Nature. Ardelean told the Reuters news agency the tools were between 31,000 and 12,500 years old. Traveling groups of hunter-gatherers lived in the area off and on for thousands of years.

Ardelean said it is possible some of the objects were even older than 30,000 years. But so far, the evidence is not strong enough to support that claim. Also, his team was unable to recover any human genetic⁴ material from the cave. "The peopling of America was a ... complex and diverse process," he told Reuters about the findings.

Tom Dillehay is a professor of anthropology⁵ at Vanderbilt University in Nashville, Tennessee. He was not involved in the study. He told The Associated Press that currently, the most widely accepted dates for the earliest known humans in North American are between 15,000 and 17,000 years ago.

A prehistoric⁶ stone tool found at a cave in Zacatecas in central Mexico is seen in this image released on July 22, 2020.

A prehistoric stone tool found at a cave in Zacatecas in central Mexico is seen in this image released on July 22, 2020.

Dillehay said the proposed date for the objects may be correct if further studies can confirm the results. However, he said he thinks they are probably not more than 20,000 years old, and most likely are between 15,000 and 18,000 years old. Dillehay does not question that some of the objects are probably man-made. But he said he would like to see further evidence of human use of the cave, such as cut bones and burned, plant-based food remains⁷.

Ruth Gruhn is a professor of anthropology at the University of Alberta in Edmonton, Canada. In a Nature commentary, she said the results should bring new consideration to six Brazilian sites proposed to be older than 20,000 years. Those age estimates are now "commonly disputed or simply ignored by most archaeologists as being much too old to be real," Gruhn wrote.

Another study is also providing new evidence that modern humans may have arrived in North America much sooner. That study centered on evidence of human presence at 42 sites around North America, as well as the position of a land bridge that connected Siberia to Alaska.

The research, also reported in Nature, suggests humans may date back to at least a time known as the Last Glacial Maximum. During that period - from about 26,000 to 19,000 years ago and immediately thereafter - thick ice covered much of the continent.

The second study also pointed⁸ to humans as the cause of extinctions of many large Ice Age animals such as mammoths and camels.

I'm Pete Musto.

Words in This Story

flake(s) – n. a small, thin piece of something

blade(s) – n. the flat sharp part of a weapon or tool that is used for cutting

spear – n. a weapon that has a long straight handle and a sharp point

archeologist – n. a person who studies past human life and activities by studying the bones and tools of ancient people

diverse – adj. made up of people or things that are different from each other

anthropology – n. the study of human races, origins, societies, and cultures

extinction(s) – n. the state or situation that results when something, such as a plant or animal species, has died out completely

1 limestone   

n.石灰石

参考例句：

• Limestone is often used in building construction.石灰岩常用于建筑。
• Cement is made from limestone.水泥是由石灰石制成的。

2 flakes   

小薄片( flake的名词复数 )； （尤指）碎片； 雪花； 古怪的人

参考例句：

• It's snowing in great flakes. 天下着鹅毛大雪。
• It is snowing in great flakes. 正值大雪纷飞。

3 autonomous   

adj.自治的；独立的

参考例句：

• They proudly declared themselves part of a new autonomous province.他们自豪地宣布成为新自治省的一部分。
• This is a matter that comes within the jurisdiction of the autonomous region.这件事是属于自治区权限以内的事务。

4 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

5 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。

6 prehistoric   

adj.（有记载的）历史以前的，史前的，古老的

参考例句：

• They have found prehistoric remains.他们发现了史前遗迹。
• It was rather like an exhibition of prehistoric electronic equipment.这儿倒像是在展览古老的电子设备。

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 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。