题目内容
______ began our new lesson.
A. But B. Such C. Thus D. So that
C
解析:
thus副词，"这样，如此"；再看一个例句：Thus ended his life.
Researchers at Sweden’s KTH Royal Institute of Technology say they have found further proof that the wolf ancestors of today’s dogs can be from southern East Asia -- findings that are contrary to theories placing the birth place in the Middle East. Dr Peter Savolainen, KTH researcher in evolutionary genetics, says a new study released Nov. 23 confirms that an Asian region south of the Yangtze River was the principal and probably the only region where wolves were domesticated（驯化）by humans.
Research data show clearly that dogs are descended from wolves, but there’s never been scientific agreement on where in the world the domestication process began. “Our analysis of Y-chromosomal（染色体）DNA now confirms that wolves were first domesticated in Asia south of Yangtze River -- we call it the ASY region -- in southern China or Southeast Asia,” Savolainen says.
The Y data supports previous evidence from mitochondrial（线粒体）DNA. “Taken together, the two studies provide very strong evidence that dogs appeared first in the ASY region,” Savolainen says.
Archaeological data and a genetic study recently published in Nature suggest that dogs originate from the Middle East. But Savolainen rejects that view. “Because none of these studies included samples from the ASY region, evidence from ASY has been overlooked,” he says.
Peter Savolainen and PhD student Mattias Oskarsson worked with Chinese colleagues to analyse DNA from male dogs around the world. Their study was published in the scientific journal Heredity.
Approximately half of the gene pool was universally shared everywhere in the world, while only the ASY region had the entire range of genetic diversity. “This shows that gene pools in all other regions of the world most probably originate from the ASY region,” Savolainen says.
“Our results confirm that Asia south of the Yangtze River was the most important -- and probably the only -- region for wolf domestication, and that a large number of wolves were domesticated,” says Savolainen.
In separate research published recently in Ecology and Evolution, Savolainen, PhD student Arman Ardalan and Iranian and Turkish scientists conducted a comprehensive study of mitochondrial DNA, with a particular focus on the Middle East. Because mitochondrial DNA is inherited only from the mother in most species, it is especially useful in studying evolutionary relationships.
“Since other studies have indicated that wolves were domesticated in the Middle East, we wanted to be sure nothing had been missed. We find no signs whatsoever that dogs originated there,” says Savolainen.
In their studies, the researchers also found minor genetic contributions from crossbreeding between dogs and wolves in other geographic regions, including the Middle East.
“This subsequent dog/wolf hybridisation（混合淡化技术）contributed only modestly to the dog gene pool,” Savolainen explains.
【小题1】What does Dr. Peter Savolainen believe?
A. Dogs’ ancestors came from the Middle East.
B. Wolves were probably first trained to work for humans in the ASY region.
C. Analysis of Y-chromosomal DNA should be combined with mitochondrial DNA.
D. Samples of the previous studies are enough to support the conclusion.
【小题2】We can learn from the passage that _______.
| A．there is a universal agreement on the place of first domestication |
| B．data from ASY may highlight where dogs came from |
| C．Dr. Savolainen’s research mainly focuses on the Middle East |
| D．the dog/wolf hybridization makes up most of the dog gene pool |
| A．It is only used in studying evolutionary relationships. |
| B．It alone can provide hard evidence for Savolainen’s research. |
| C．It is the most useful in finding out the birth place of dogs. |
| D．It comes from the mother of most animals and plants. |