Human Diaspora (Report)

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Humans are a rather strange species. They are widespread, but seemingly with no traceable origin.
This, of course, ignores all known laws of biology. Humans must have evolved from somewhere. Divergent evolution is possible, but heavily improbable, to have created humans so far spread throughout the galaxy and at the same rate of evolution.
Take, for example, some of the known human colonies:
*Planet Cydonia. It is known to have been colonized by Jeremiah Joseph Plumm, but, where did he come from? He will not tell.
*My home planet, Arcadia.
*The City of Lore itself may even be a human colony.
I know from my own experience that 
I have met several hundreds of humans, especially in the City of Lore, who claim to be natives of Earth; yet, none can agree on the precise location of this planet. Wanting to trace my own origin, I followed their claims.
This adventure yielded fruitful results, but more questions than anything else. Upon scouring the galaxy, I found multiple "planet Earths". Each possessed an identical geography, identical levels of technology, identical ecology, and identical history and culture. The only changes seemed to be in the location of these planets.
Were they cloned, and then their populations replaced with spliced mixes instead?
Another observation: these "planet Earths" scattered throughout the galaxy do not seem capable of producing colonist ships on their own. 
These questions led me onto a "eureka moment". There must be a progenitor Earth. The other alternate Earths must have been cloned from this progenitor Earth, and the colonies must have been produced by it.
I thus turned to the colonies for answers. Most colonies retain the same folklore about the planet Earth - that it is located in the "solar system" within the "Milky Way Galaxy". 
In the wreckage of the colony ship on my home, Arcadia, I even found some coordinates, though the ship's navigation log had been scrambled after traveling through a wormhole.
Upon further searching, I did find a Milky Way Galaxy, and a Solar System, next to the Origin System. It was complete with its own link-up to the Intergalactic Highway System. However, where I expected to find this progenitor Earth, I found nothing but rubble and burgeoning alien communities on the neighboring planets (Mars, Venus).
Was this the planet of my ancestors?
Was this the progenitor Earth?
==Notes==
*Traveler Blue, please rescind information on "cloned Earths" theory. Those who were not native to the original progenitor Earth might find this information distressing. --
*If you would like more information, please ask Kashmir about the world tree.