In my universe, history begins on the plains of Shinar where the human race gathered under the guidance of Nimrod to build a tower—a tower that came to be called Babel.  I date this to around 4500 BC. 

At that time, the young gods (children of the Nature Spirits called the Titans) fretted that the rest of the world was somewhat emptied of self-directed life.  Thus they imported other “people” to fill the spaces.  These included the Centaurs, Mermaids, Fauns, and many others, including the Were people: shape shifters located in Eastern Europe and Southern Russia.  The gods acclimated these various strange people to life on earth, redesigning them , more or less, to fit in to their new environment. 

The Were, for example, learned to shift into the shapes of omnivores and carnivores (predators) native to this planet.  What such animals might have been native to their home planet was unknown, even to them.  For daily life

Of course, when the tower fell and the human race was scattered around the globe, that had to be accommodated for by the over-zealous gods.  In time, the human race put pressure on these other “peoples,” limiting their range and competing for resources.  One thing that happened was the inter-breeding of the species.  (The gods acclimated the various peoples according to the human mode they had available which made inter-breeding possible).

Eventually, the gods deleted these non-humans by various means in order for the human race to have the world according to the original design.  What they did not foresee, however, was the transmission of a recessive Were gene among the human population, nor the virus associated specifically with the Were wolf form, that could lay dormant in the earth for thousands of years.  It is a very rare person who carries the gene, and rarer still are the ones who contract the virus, but when they do so together…

Of course, the human species, in bones and muscles, is not designed to transform its shape.  It is very painful.  What is more, the Were were adept at taking on the characteristics of the beasts they portrayed; but for a human to think like a wolf is shear madness.  More than wolf, though.  Human wolf.  An insane, intelligent killing machine.  A werewolf.

From Rome Too Far, the Tale of the Traveler, Greta:  After the Werewolf

Hans waited for her where the road turned.  After the obligatory, “What kept you?” they crossed the last, short meadow to Mother Hulda’s house.  All the while, Greta shook her head.

“Something’s spooky.”  Hans said.  Even he felt it.  When they saw the house, the feeling intensified.  By the time they reached the porch, Greta could hardly keep from turning and running away.  She stopped at the door and told Hans to get behind her.  He did not argue. 

When she opened the door, she screamed, and this time she knew what she was screaming about.  There were bits and pieces of Mother Hulda thrown all over the room.  Her head was on a corner of the bed, facing the door.  One eye was missing, but she stared at them with the other.

Greta could neither move nor stop screaming.  Hans pushed passed and promptly threw up behind the door.  That probably saved his life.  There was a noise in the back room.  A man shuffled out of the dark.  His eyes were wide with madness.  He was naked and filthy, and he looked as if he had been burned everywhere.  His body was covered with sores and open wounds where there had once been blisters, and his face looked like it had been melted. 

Greta still screamed but her legs were like rubber.  She could not abandon Hans.  She could not move.  She cried out for help, and someone answered from deep in time. 

The madman clearly sensed the change.  He sniffed and howled after a fashion before he dove through the window and headed toward the forest, moving at a speed which was remarkable for a man who was half dead.