[b]A a History of Mankind - Up to year Zero[/b]

Humans are a species who historically orbited a G class star in the orion arm region.  Humans developed rapidly from hunter gatherers to a space faring species in the span of seven thousand years.  Humans are warm blooded sapient animals of mammalian descent that are upright walking and bipedal, and still are despite the dangers of space travel and having nearly gone extinct In the past three thousand years alone when their industrial society got so advanced they discovered nanotechnology a century too soon for their own good.  

Their home world, earth is now but a massive, spherical grey blob where nothing lives due to simply being the size of countless nano machines who's current state is unknown (for now).  The human race survived simply because there was twelve colony ships sent out as the nanomachines begun to slowly over the span of five decades eat away at the planet- solving the nanomachine problem using nuclear weapons and Electromagnetic devices only temporarily slowing down the technological cancer.  So instead the typically individualistic human species collectively begun building ships that would transport tons of eggs and frozen people to distant worlds around the Galaxy believed to have life.  

(Colonizing Mars being considered a stupid idea because many scientists feared the nanomachines may one day spread to Mars as well, the census among every human after the nukes didn't work as well as hoped being "get the fuck as far away from sol as possible") 

Tragically only two thousand people were able to go on these ships, all of which having to be rigorously trained "colonials" who could properly manage everything on the massive ark-like ships and their vast DNA banks.  For these ships will be going on a vast journey that will put humans on every corner of the Galaxy by the time we get to year zero.  The humans back on earth kept desperately trying to kill the nano machines to little avail while others kept making more colony ships to go out to the other worlds of the solar system with more people, the humans on earth left perishing.  How humans developed from the colonies shall be seen.

(TL;dr nanomachines nearly killed everyone so we colonized the Galaxy with twelve good ships- this means the hard limit on human civs is 12-13, however.  Anyone who wants to be human can pick the world colonized and detail how that colony developed after.  All the colonies started with over a hundred humans, have access to data records of numerous technologies (and how to build them) and a library of genes to seed a planet with over time. They also have some equipment, but the equipment was much less standardized than the gene libraries and archives.)