Because of Colonial and then United States expansion across North America, the Native American population has been forced to adapt and change to survive. At first, with the government forcing tribes to remain on designated reservations, much of Native American culture continued as before, but as technology and time moved on outside the reservations, more and more of their people left the tribes and lost touch with traditions.
The many Native American languages have changed with the years, but there are still speakers and teachers of the original dialects in many areas. A great number of local dialects have been lost; others are known by only a few people. In fact, the surviving languages were so foreign to Western ears that Navajo people were drafted by the U.S. Military during World War II to transmit messages in their own Native American codes; these were virtually unbreakable. What languages survive of the originals have been mostly kept intact by the teachers and students who learn them by ear and pass them on to their own students; the slight changes that occur from such unwritten learning is part of language evolution. However, those languages are almost extinct today, as English and Spanish have become the common languages in the U.S. and surrounding countries.