New Discoveries Suggest Earlier Settlement of Americans

    The first human inhabitants（居民） of North America settled at least 2,500 years earlier than the people previously¹ identified as the first Americans. So say archaeologists, who have unearthed² a trove³ of stone artifacts belonging to the early Americans at an archaeological（考古学的） dig in central Texas, in the U.S. southwest.
    The 1,600 ancient stone artifacts, including chipping debris⁴ and flecks⁵ from sharpened arrow points and so-called bi-facial knife blades, were found lying undisturbed at an archaeological site over 60 kilometers southwest of Austin.
    Michael Waters, director of Texas A & M University’s Center for the Study of First Americans, led the dig at the site near the head of a small stream in what’s come to be known as the Buttermilk Creek⁶ Complex.
    Waters say the latest relics⁷ were buried in a clay layer beneath sediment⁸ containing artifacts of the Clovis people, thought to have lived in this region between 1,200 and 1,300 years ago and been the earliest American settlers.
    But Waters say the stone artifacts include a wide variety of tools dating as far back as 15,500 years ago. "We found many, many chisel-like tools, indicating that people were working bone, working wood, you know, many hard materials," he said.
    Archaeologists used a technique called luminescence dating to show when the early settlers arrived.  The technique measures light energy trapped in sediment grains surrounding the tools from the last time the layer was exposed to sunlight.
    Evidence of Clovis people were first discovered in 1932, and ever since, Waters says, archaeologists have argued about whether other sites also belonged to the Clovis civilization or were older, unrelated settlements. Waters says his team’s findings validate⁹ those who argue for an earlier colonization¹⁰ of the Americas.
    Waters says the presence of prehistoric¹¹ humans in the Americas more than 15,000 years ago doesn’t challenge the current theory that humans migrated out of Africa, moved east through Asia and on to the Americas over a Siberian land-bridge to Alaska.
    But he says it could mean that the instead of a land bridge, the earliest settlers used boats to come to the Americas.
    "By 15,500 years ago, the ice-free corridor, that land corridor connecting Alaska with the mainland of the United States, was closed.  The two ice sheets had merged¹².  So, the only route you could take to get south of those ice sheets and down into what is now the continental¹³ United States you would have had to have taken a boat.  So, I think this clearly shows that people must have arrived in the Americas by boat.  The earliest Americans," he said.
    An article on an earlier settlement of the Americas is published this week in the journal Science.(本文由在线英语听力室整理编辑)

1 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

2 unearthed   

出土的（考古）

参考例句：

• Many unearthed cultural relics are set forth in the exhibition hall. 展览馆里陈列着许多出土文物。
• Some utensils were in a state of decay when they were unearthed. 有些器皿在出土时已经残破。

3 trove   

n.被发现的东西，收藏的东西

参考例句：

• He assembled a rich trove of Chinese porcelain.他收集了一批中国瓷器。
• The gallery is a treasure trove of medieval art.这个画廊是中世纪艺术的宝库。

4 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

5 flecks   

n.斑点，小点( fleck的名词复数 )；癍

参考例句：

• His hair was dark, with flecks of grey. 他的黑发间有缕缕银丝。
• I got a few flecks of paint on the window when I was painting the frames. 我在漆窗框时，在窗户上洒了几点油漆。 来自《简明英汉词典》

6 creek   

n.小溪，小河，小湾

参考例句：

• He sprang through the creek.他跳过小河。
• People sunbathe in the nude on the rocks above the creek.人们在露出小溪的岩石上裸体晒日光浴。

7 relics   

[pl.］n.遗物，遗迹，遗产；遗体，尸骸

参考例句：

• The area is a treasure house of archaeological relics. 这个地区是古文物遗迹的宝库。
• Xi'an is an ancient city full of treasures and saintly relics. 西安是一个有很多宝藏和神圣的遗物的古老城市。

8 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

9 validate   

vt.（法律）使有效，使生效

参考例句：

• You need an official signature to validate the order.你要有正式的签字，这张汇票才能生效。
• In order to validate the agreement,both parties sign it.为使协议有效，双方在上面签了字。

10 colonization   

殖民地的开拓，殖民，殖民地化； 移殖

参考例句：

• Colonization took place during the Habsburg dynasty. 开拓殖民地在哈布斯堡王朝就进行过。
• These countries took part in the colonization of Africa. 这些国家参与非洲殖民地的开发。

11 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。

12 merged   

（使）混合( merge的过去式和过去分词 )； 相融； 融入； 渐渐消失在某物中

参考例句：

• Turf wars are inevitable when two departments are merged. 两个部门合并时总免不了争争权限。
• The small shops were merged into a large market. 那些小商店合并成为一个大商场。

13 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。