Many Native Americans closely resemble Asians. This has led most scientists to (1) believe something about Native Americans. They think that most Native Americans (2) from a distant group of people. These people (3) from Siberia across the Bering Strait, between 17,000-11,000 years ago. The exact time and   4   is still under question. That is, it is still a(n) (5) of debate. The time they traveled and the route they took is still being argued, as is whether it happened (6) . (7) recently, some anthropologists (人类学家) argued that the migration occurred 12,000 years ago. However, there are a number of difficulties with this theory — (8) particular, the presence of people in the Americas earlier than one might think. There is growing evidence of human (9) in Brazil and Chile 11,500 years ago or earlier. There is also (10) of humans living in the Americas some 50,000 years ago. (11) , other possibilities have been suggested. They may have (12) the land bridge several thousand years earlier or they may have sailed along the western coast. However, some (13) this theory. They think that humans (14) skills for sailing during that era. Some consider the genetic and cultural evidence for an Asian origin overwhelming. It should be noted, (15) , that some other people are very upset at this idea. Many present-day Native Americans (16) the above theories. They say those who put forward such theories have political (17) They have their own traditional stories that offer (18) of where they came from. Their own stories claim that their (19) are different from what scientists say. Those accounts, though, have mostly been (20) by scholars. Therefore, the origin of Americans still remains a mystery to be explored.