What was the most commonly accepted theory of the indian origin in north american?

Migrated across a land bridge from Russia to Alaska. 

This common belief has been challenged in recent years with more archaeological information coming from South America showing ruins older than any in North America. There are some historians who believe people may have come by boat and settled the land before the migration across the land bridge. 

hope that i helped :)

Native Americans ("Indians") migrated from Siberia across the Bering Strait, which during the last ice age was dry land. The exact time period isn't known (I believe the most commonly accepted date is about 10,000 years ago). Also, there were probably multiple migrations (at least three) based on linguists' analysis of current native American languages.

the protestant reformation's started in 1517, disturbing the religious and political order in europe´s catholic countries. the outcome was the european wars of religion prosecuted in europe in the 16th, 17th and part of the 18th century. nonetheless, uprisings, territorial disputes, and great power conflicts were also causes of the wars.  

d. it adversely affected american productivity