Earth was the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and was the original home world of the human race. Earth has been at the forefront of galactic history, being involved in several Robotech wars. Earth was home to several billions of humans prior to the Zentraedi Holocaust, which wiped out approximately 70% of the Earth's surface. The remaining human population since then have been divided among several independent states that interact through diplomacy, conflict, travel, trade, and media.
The Earth first formed about 4.6 billion years ago, and gave rise to the first single-celled organisms about 3.9 billion years ago. About 200,000 years ago, the ancestors of modern humans, Homo Sapiens, evolved in Africa. Indigenous to Eastern Africa, they gradually spread across the entire planet. Eventually, the humans, originally consisting of groups of hunter-gatherers, began to develop into civilizations.
Human civilizations gradually became more and more complex, and in 1999, an alien battlefortress crash landed on the planet's surface. Humanity studied and reverse-engineered the mostly-intact techno-systems of the ship, which gave birth to the advance science of Robotech. Ten years later, the First Robotech War broke out with the Zentraedi, who came to Earth to retreive the fallen battlefortress. Humanity ended as the victors, but at a great cost. The majority of Earth's surface was devastated by the Zentraedi Holocaust. In the end, a little over a hundred million humans survived the conflict.
Humanity could no longer ignore its place in the galaxy, so over time, citizens began leaving Earth to live amongst the stars. Earth's importance waned, and subsequent wars and invasions by alien forces further reduced the planet's economic and political significance.