I would refer you to Dr. John Bradenburg’s work. this link is one of many regarding the stories of his theory. I have his original presentation somewhere in my computer. http://www.dailymail.co.uk/sciencetech/article-2843871/Ancient-Martian-civilisation-wiped-nuclear-bomb-wielding-aliens-attack-Earth-claims-physicist.html
Some of the Utopians obviously escaped and made it to Earth. They now call themselves Progessives.