The inland route theory–known as the “Ice Free Corridor”–suggests humans moved across present-day Alaska and the Yukon, then took a right turn between two huge ice sheets. They then traveled along the British Columbia/Alberta border into the northern Plains of the present-day United States.
The other “North Pacific Route,”also known as the “Kelp Highway,” said humans traveled along the west coast of North America.“We can’t exclude either coastal or inland routes for the first Americans,” study lead author, Potter said. “I suspect both probably were used.” He added that “what we wanted to do was to provide a way to discuss the traveling process–not based on speculation but rather on a careful and critical review of the current evidence we have.”
“There really is growing archaeological record and the genetic records,” he said. “As researchers from different fields work together in a respectful and beneficial manner,” the study said,“the opportunities to analyze additional human remains to infer population history in the Americas grow.”
Current evidence shows that there are three primary branches of Native American ancestors. One group, southern Native Americans, walked through all of North and South America. Another group, northern Native Americans, are present now in northern parts of North America. A third group, Ancient Beringians, were located in the far north, in Beringia and present-day Alaska and the Yukon Territory.
And as for when this all happened, the data suggests that “traveling occurred between 16,000-14,000 years ago,” Potter said. The study argued that more research is needed to determine how the migration occurred. “We’re saying there’s not enough evidence yet–we need more science on both routes.”
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1.Which place is in the route of the “Ice Free Corridor”?
A The northern Plains.
B The west coast of North America.
C The Pacific coast.
D The Kelp Highway.
解析：选A。细节理解题。根据第二段第二句They then traveled along the British Columbia/Alberta border into the northern Plains of the present-day United States.可知北部平原是在内陆路线上，故选A。
2.What is the aim of Potter’s research?
A Deciding either coastal or inland routes.
B Giving people the chance to know truth.
C Collecting the current money he needs.
D Discussing places of Columbia/Alberta.
解析：选B。推理判断题。根据第三段第四句的what we wanted to do was to provide a way to discuss the traveling process–not based on speculation but rather on a careful and critical review of the current evidence we have可知他的研究目的是为了让人们了解真相，故选B。
3.What is the advantage of Potter’s research?
A Researchers from different fields work together well.
B Researchers analyze human tools to tell their history.
C Researchers don’t consider the archaeological records.
D Researchers don’t know which route is the right one.
解析：选A。推理判断题。根据第四段第二句的As researchers from different fields work together in a respectful and beneficial manner可知他们的研究优势是不同领域的研究者能共同协作得很好。
4.What is the purpose of writing Paragraph 5?
A To tell the results of data.
B To introduce different groups.
C To know when this happened.
D To find out how the migration occurred.
解析：选B。目的意图题。根据第五段第一句Current evidence shows that there are three primary branches of Native American ancestors. 可知该段主要是介绍不同的族群，故选B。
