One of the stories I have outlined in my Magic Folder deals with exactly this issue. Origin of Species.
Since it's unlikely that I'll be writing it very soon, I'll reveal the HUGE spoiler!
If you like it, then feel free to adopt it.
In the early years of the 22nd century, mankind had made great leaps in space exploration and technology and had tapped into the hyperspace realm. In those days it was all very very carefully controlled and misjumps were common, with ships disappearing on a regular basis
Ruthless corporations and varying government types fought for control of space. One such corporation was TAC Biogen, a corporation that specialised in adapting Earth lifeforms for survival on other planets. They developed hybrid lifeforms by gene splicing different genetic information from a variety of Earth's creatures.
You can probably see what's coming now...
TAC Biogen had a large fleet of seeder ships that were intended to be used to seed plant and insect life onto various explored worlds in order to make them viable for either colonisation or harvesting. TAC, however, went one step further and planned to introduce thier own cloned lifeforms to worlds that already had suitable atmospheres. They designed and built a new fleet of Deep Space Cruisers that were ostensibly hyped as seeder and exploration ships with a mission to analyse planets and introduce the appropriate small life forms.
The fleet launched in the mid 22nd century (2160s or thereabouts) with a cargo of hybrid lifeforms ready for introduction. What hadn't been made public was that half of the ships' cargo was hybrid sentient life. Felinoid, insectoid, amphibian and avian, all cross developed with humanoid DNA and creating a wide variety of phenotypes ready to introduce as civilisations. The cloning and growing process included direct learning via neural links. In theory, the cloned lifeforms could be introduced to a planet with suitable atmosphere and equipment and build a sentient civilisation with what they had to hand.
The ships spread throughout local space (Galaxy 1) rapidly, usually via deliberate misjump, introducing these life-forms everywhere. There was no pattern to it, merely the random chance that misjumping introduced.
In time these colonies thrived. They developed thier own technology and were soon spacefaring races in thier own right, accelerated by the knowledge they had been given by thier unknown benefactors. None of these races knew their true origin.
In time, humanity's main colonisation and exploration efforts reached out to the group of worlds that would come to be known as the Old Worlds. One of these worlds, Diso, was home to a felinoid race that claimed to have been there for millennia. The planet Lave was colonised first, and the colony governors there made a solid alliance with the Disans, learning about the area of space they inhabited and their history.
In the late 2480s the Federation demanded that Diso be given over to them as a human colony and the Disans be relocated to another felinoid world. Diso's rich mineral andagricultural value was to blame, but the Disans resisted the action, reluctant to leave their homeworld. The humans on Lave agreed and refused to back such an action. In 2491 The Federation retaliated in force, sending a fleet to capture Diso. The Lave colony and other human colonies in the Old Worlds region stood with the Disans and fought off the invading Federal forces. The battle was short and violent and many were lost on both sides. Eventually the colonists prevailed and the Federation retreated. The worlds in that region declared thier independence from the Federation and declared that they would stand against any such attempt to annexe worlds of the non-humanoid races by any government. They stood for independence and fair treatment to all. They formed the Far Colonies Alliance and sent envoys to every non-human world to ask them to join in a mutual defence pact. This was highly successful and many worlds joined, including a high number of human colonies who agreed with the stand the FCA was taking against the increasingly xenophobic Federation.
The Far Colonies Alliance grew, becoming one of the largest and fastest growing governments in known space. Members signed up from regions far from the Old Worlds area, including other Galaxies (as they were thought to be back then), and the name Far Colonies Alliance seemed to be outdated. A new, more galaxy-spanning name seemed apt.
The Galactic Co-operative of Worlds was born...
ironically, this is stuff that will be dealt with in the next but one story - an old DSC is found in Galaxy 3 and the whole history is discovered.
I'll be posting this stuff to my site soon, now that it's public...
There are millions of unpopulated worlds in the Elite universe. They just aren't shown on maps. What would be the point? The Dark Wheel showed that there were worlds in existence that were not shown on the maps. Federation and Imperial worlds are not shown either. Note that Elite shows a map of member planets, not systems - systems may contain other planets that are either not inhabited or not members of GalCop.
Humans are listed in Elite as Human /Colonials/... Thus ALL humans are colonists, originally from Earth/Federation.
Thargons (or Thargoids, to name them properly) are insectoids. Whether or not they were part of the original genetic experiments is open to debate, but I personally didn't include them. In the galaxy at large there are some native species out there, and I think the Thargoids should be one of them. Having said that, maybe they found out long ago that they were an abandoned human experiment. Maybe not though.
Galaxy 1 is indeed adjacent to the region of Sol. I have a map that shown exactly where the G1 map is in relation to Earth. Note that Achenar (home of the Empire) is actually within the boundaries of G1!
I think I went over once before what happens to the other races between the events of Elite and Frontier. If I haven't put it online publically then let me know and I'll do it. It covers what actually happens to bring GalCop crashing down and how things change so much between Elite and Frontier in more detail than the UTF stuff.
I have a second timeline document that I haven't made public, since it covers the timeline and events of my stories (including ones I have outlined but not written yet). Since my writing time is decreasing by the day, I might publish it for people to see and use if they want. I never thought that the original Unlocking the Frontier stuff would be so widely used! Thanks, guys!