Christopher Columbus was not the first European to set foot in this hemisphere. But, what he did clearly set off what historians refer to as the Columbia Exchange. This was a worldwide event, that involved more than just Europe and the Americas. It was one of the major factors in creating the world we have today. Human migration usually involves some type of conquest; somebody wins, somebody loses. Whether it is Celts or Indo-aryans or Incas or Aztecs, somebody pushed someone else out and takes over. It is history and it is good in the end because we are who we are because of that.