For many years, scientists have thought that the first Americans came here from Asia 13,000 years ago, during the last ice age, probably by way of the Bering Strait. They were known as the Clovis people, after the town in New Mexico where their tools were first discovered in 1929.
BUT, there is mounting evidence of pre-Clovis settlements. The journal Science is reporting that excavations show hunter-gatherers were living at the Buttermilk Creek site in Texas and making projectile points, blades, choppers and other tools from local chert for a long time, possibly as early as 15,500 years ago.
This means that a lot of people that we thought were raging lunatic hill-people were actually right this whole time!
For more info about tool usage and evolution, click here: www.sciencemag.org/content/331/6024/1512.summary