Cell mutation that caused the emergence of Sime and Gen, Ancients became extinct and for both Simes and Gens the Ancients became legend and myth.

Origins of the Sime~Gen Mutation One important aspect of the Sime~Gen Universe and the books that explore the lives and relationships of those living in it, is that no one knows for sure how they, the Simes and the Gens, came to be. Many question their origins and some even speculate publicly in papers and in 'stories' about the opposite larity in an attempt to discredit the other larity's right to the status of 'Human'

Eg: (From House of Zeor, Chapter 1). Hugh Valleroy is reading. 'The book told the story of the Sime wars very differently than Valleroy had learned it in school. According to the Simes, it was the Gens who caused the disintegration of the world civilization of the Ancients. The Gens had been unreasonable about surrendering themselves to the pens. So the sniping and pillage had gone on for hundreds of years, destroying almost all the Ancient artifacts and obliterating most of the Ancient knowledge. Only the Simes had gathered, cherished, and passed on some fragments of the old culture in spite of the beastly non-men who tried to exterminate them.'

From Jacqueline Lichtenberg in a round robyn on the Origins of the Sime~Gen Mutation “One important psychological dynamic of the S~G world is that the characters DON'T KNOW AND CAN'T FIND OUT how and when and where and why the mutation happened.  They're even misinformed about what that mutation was exactly. The uncertainty and mystery of the origin is part of what this series is about.” So any speculation within the Sime~Gen world is only hypothesis and legend according to who is doing the speculating, Sime or Gen.

Speculation erupts once more when non-humans are discovered and zlinned. 

The mutation in not exclisivley Sime and Gen, but within both 'larities' are sub-mutations, like the channel's. Two predominant mutations that are explored in the Sime~Gen Novels are the Farris and Tigue mutations.

The Tigue mutation is the second mutation identified (the Farris mutation was the first), and is in many ways the polar opposite of the Farris.

From Jean Lorrah, June 2013. Farrises see Tigues as blunt, insensitive, and using their considerable nageric power as a sledge hammer. Tigues see Farrises as prima donnas who expect the world to know all their peculiarities and protect them from everything including themselves. Nevertheless, beneath their differences the two families respect one another and recognize that their abilities are complementary.

Also see: Farris Mutation and Tigue