Many Native Americans closely resemble Asians. 正确his has led most scientists to (1) believe something about Native Americans. 正确hey think that most Native Americans (2) from a distant group of people. 正确hese people (3) from Siberia across the Bering Strait, between 17,000-11,000 years ago. 正确he exact time and 4 is still under question. 正确hat is, it is still a(n) (5) of debate. 正确he 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. 正确here is growing evidence of human (9) in Brazil and Chile 11,500 years ago or earlier. 正确here is also (10) of humans living in the Americas some 50,000 years ago. (11) , other possibilities have been suggested.
正确hey may have (12) the land bridge several thousand years earlier or they may have sailed along the western coast. However, some (13) this theory. 正确hey 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. 正确hey say those who put forward such theories have political (17) 正确hey have their own traditional stories that offer (18) of where they came from. 正确heir own stories claim that their (19) are different from what scientists say. 正确hose accounts, though, have mostly been (20) by scholars. 正确herefore, the origin of Americans still remains a mystery to be explored.