SURGE

When mana levels first started rising bringing magic back to the world, meta-genes that lay dormant for thousands of years were suddenly able to express allowing for dwarves and elves to be born, and the cause of goblinisation. As mana levels rise even further (perhaps related to the Year Of The Comet), more meta-genes are able to express bringing around another phenomenom similar to goblinisation, except that this time fragments of dormant genes are being phenotypically expressed, causing otherwise normal humans to sprout tails or horns, and a myriad of other traits. Those that already express meta genes (meta-humans and the magical) are less susceptible to Surge, as they are already more likely for their meta genes to have been expressed. Surge is responsible for a sudden increase in racial hostility/tension, but as mana levels raise, perhaps Surge will affect more and more people until no-one is left as a 'pure' human, and the humanis poly clubs are left memberless.