Races as breeds, not species?

[Ilium]

This is pretty much how the races in my campaign originated. Rather than specially-bred slaves, the main races emerged from a base stock tinkering with its own genetics. The original culture was at about the same level as Eberron (or maybe even a bit more advanced) but eventually tore itself to bits in a big war. Civilization collapsed and a long dark age enveloped the world. Eventually the elves (who were the only ones to preserve any vestige of the original culture) got their act together and started "liberating" the world from the orcs and goblins that dominated it through their large numbers and bad attitudes.

What they don't tell anybody (and in fact most modern elves don't know) is that they started the war in the first place, and their main enemies (the goblins) were actually the original base stock that all the other races were developed from.

 

[Umbran]

Random tangent, this model for interbreeding is weird to me.... it's like the end of ?Hooch? (cheesy cop + dog film starring Tom Hanks and a lot of drool) where the litter of puppies is 4 pups that look exactly like the mom and one that looks exactly like the dad. Mixed breeds don't work that way.

Well, in Shadowrun it isn't a purely genetic thing - there's magic involved, powerful enough to transform a fully-grown adult human into an orc or troll. There's no reason to think that a magical interaction with genetics has to follow the rules we currently know.

Your plan also sounds reminiscent of Larry Niven's Ringworld, which has a whole mess of humanoid species spun off the same common root - the Pak.

The Pak have an interesting twist: They come in two forms - Breeder and Protector. The original Pak breeders are barely sentient humanoids (think caveman), after they're beyond breeding age, if exposed to the roots of a particular plant (the "tree of life"), they transform into Protectors - which are highly intelligent, immensely strong and physically fit, technologically advanced, and have an obsessive drive to protect their genetic relatives - the more closely they are related, the strong the urge to protect.

Humans are what you get when a Pak ship crashes on earth, and all the Protectors on board are killed, but Breeders survive. Most of the signs of human old age are incomplete expressions of the protector form, which cannot be complete without the Tree of Life. On the Ringworld, the Protectors all got killed off, and the breeders started filling in various ecological niches.

So, to be analogous, the Protectors would be your ancient master race...