The Silver Millennium (era)
The Silver Millennium is the occult name for the historical era of the Sol system spanning from 20300 BCE to 8102 BCE. Little remains of this hidden period of time when Humanity and the Selenite peoples reigned in supremacy. Those who are "in the know" are seldom credited for the information and artifacts they can uncover from this time, as it conflicts starkly with conventional/modern anthropology's understanding of the Mesolithic era.
Matsuo Shin is the premiere archaeologist of this hidden history, though not the only one.
Common reckoning establishes the Silver Millennium with the arrival of the Selenos Dynasty in exile in the year 20300 BCE. When they arrived in the Sol system, they found two of the many planet-sized objects already inhabited by sophisticated sapient peoples: Mars by the species known as Ice Warriors, and Saturn by the Saturnians; Quinox, though inhabited by a sapient race, was still shrouded by its protectors. After assessing the state of the solar system, the Selenites chose the resource-rich world now known as Earth to serve as their base of operations, establishing their primary colony there.
Relations with their neighbors were initially turbulent. The Ice Warriors, still in the throes of their cultural obsession with war and still very resource-starved, attempted a number of raids on early Selenite resource-gathering facilities. Although the Selenites were few, they retained all of their arcano-martial prowess; with the Ginzuishou backing their defenses, the Ice Warriors quickly learned respect for their new neighbors, and were eventually convinced of the profits to be had from alliance. The Saturnians (INSERT IF AND HOW THEY MET HERE -- ED).
Within two hundred years, the Selenite dynasty had solidified its colony on Earth's moon to the point where the Dynasty could consider the future. Selenites, encouraged by the Dynasty to reproduce much more frequently in these early years, were starting to consider new horizons; the many uninhabited worlds were earmarked for colonization and settlement. More concerningly, early Selenite archaeological investigations of Earth yielded that its two major species, the Youma and the Humans, were only the latest in a long line of weird and terrible beings to dominate the planet. The Selenite Dynasty decided to subtly influence the evolution of Humans to more closely approximate the Selenite physical and psychological norm (a process commonly referred to as Uplifting by modern sci-fi buffs), possibly to gain the assistance of a client species, but also to ensure that the forerunners slumbering on Earth stayed that way.
In the year 19600 BCE, Selenite astronomers observed the rapid approach of a rogue planet into the Sol system. While its arrival did scatter many Oort cloud planetoids, it was barely noticed by other sapients. The Selenites, still possessed of the swiftest space-faring vessels, investigated; against all plausibility, they detected a single, tremendously powerful life force/spirit presence: the nascent Princess Venus, newborn but already very mature. Lacking explanation or evidence to suggest why this planet had appeared, the Selenites adopted Venus into the courts, and included Venus in the plans for future colonization.
By 19103 BCE, Selenite colonies and outposts had been established on most of the major worlds of Sol: Mercury, Venus, Mondas, Jupiter, Neptune, Uranus, and 134340 Pluto. Trade outposts were established on-world with the Martian and Saturnian peoples. While these outposts did nominally answer to the Selenite dynasty, they were given significant leeway to determine how they wished to handle their affairs.