Earth: the little blue planet that we call home. It has faithfully orbited the sun for nearly 6 billion years and has weathered many changes throughout that incomprehensible amount of time. And even though scientists and researchers have learned a great deal about the history of earth, there are still more questions than there are answers at this point. Humans are often thought of as the most evolved species in the history of life on earth. But what the history books don't tell us is, there is a distinct possibility there were advanced civilizations that existed on earth for millions and even billions of years before modern man. Mass Extinctions, Evolution, and Forbidden History We are taught that life slowly evolved from single-cell organisms, eventually becoming a wide variety of species because of earth's ability to sustain lifeforms, along with life being able to adapt to any given environment. But we also know that earth's environment isn't always so forgiving, there have been