Read the following article and answer the question. Article: When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science. Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard of the Smithsonian Institute, used DNA material--some of it unearthed by miners in Alaska--to conclude that today's domestic dog originated in Asia and accompanied the first humans to the New World about 10,000 to 15,000 years ago. Wayne suggests that man's best friend may have enabled the tough journey from Asia into North America. "Dogs may have been the reason people made it across the land bridge," said Wayne. "They can pull things, carry things, defend you from fierce animals, and they're useful to eat." Researchers have agreed that today's dog is the result of the domestication of wolves thousands of years ago. Before this recent study, a common thought about the precise origin of North America's domestic dog was that Natives domesticated local wolves, the descendents of which now live with people in Alaska, Canada, and the Lower 48. Dog _ from a Fairbanks-area gold mine helped the scientists reach their conclusion. Leonard, an evolutionary biologist, collected DNA from 11 bones of ancient dogs that were locked in permafrost until Fairbanks miners uncovered them in the 1920s. The miners donated the preserved bones to the American Museum of Natural History in New York City, where they remained untouched for more than 70 years. After borrowing the bones from the museum, Leonard and her colleagues used radiocarbon techniques to find the age of the Alaska dogs. They found the dogs all lived between the years of 1450 and 1675 A.D., before Vitus Bering and Aleksey Chirikov who were the first known Europeans to view Alaska in 1741. The bones of dogs that wandered the Fairbanks area centuries ago should therefore be the remains of "pure native American dogs," Leonard said. The DNA of the Fairbanks dogs would also expose whether they were the descendents of wolves from... Question: What does the passage mainly talk about _ . Answer:
Select from:
[I] the origin of the North American dogs
[II] the DNA study of ancient dogs in America
[III] the reasons why early people entered America
[IV] the difference between Asian and American dogs
Answer:
[I]