听力音频：
L1
讲座
1. What does the professor mainly discuss?
A controversy surrounding an archaeological discovery
A theory about the early migration of humans to North America
Possible causes of the extinction of North American mammoths
New research tools for dating ancient artifacts and animal bones
2. What does the professor imply about the discovery of mammoth skeletons?
Stone artifacts are often found with mammoth skeletons.
More mammoth skeletons have been discovered in North America than elsewhere.
Mammoth skeletons are typically found in places like creek beds.
It is rare to find a complete mammoth skeleton
3. What does the professor imply about the methods used in the excavation of the mammoth skeleton?
They took more time than methods that are used today
They probably harmed the investigation
They formed the basis for later advances
They were originally developed by geologists
4. What was the significance of the fact that there was no collagen present in the piece of bone that the researchers analyzed?
It meant that carbon dating could not be used to determine the age of the bone.
It meant that the bone came from a different site
It meant that the mammoth was older than anyone tad thought
It meant that collagen had probably never been present in the bone.
5. What did the 2002 analysis of the sediment samples tell the researchers?
When the stone tool was placed at the site
What the climate conditions were 300,000 years ago
How long the mammoth skeleton had been buried
When the last North American mammoth died
6. What did the researchers conclude based on their investigation of the stone that was found with the mammoth?（多选题）
The tool was probably authentic.
The tool was made from stone from a distant location
The tool could not have been used to kill the mammoth.
The tool was never actually used for its intended purpose.
