UFO's are said to have come to earth for thousands of years. No one thinks that any lifeforms in UFO's would harm humans in any way because they haven't done it yet and they had PLENTY of opporotunity! A theory some people and scientists have is that the lifeforms in UFO's are waiting until humans are more civilized and advanced and of course we've been progressing through the years. When we are more advanced the lifeforms may land and communicate with us. (Remember that is only a theory!) There is evidence everywhere that other lifeforms exist in paintings, on rocks, crop circles, etc. I of course will really want to meet these lifeforms when the time comes! That is, if the time comes...