2520th Turn- Avis and Distruction of Thread.

History of Pern 2520-2538 according to the books.
This is where our Pern begins to differ from Anne's. In the book "All the Weyrs of Pern", Lord Holder and Rider Jaxom and His white dragon Ruth go between to several periods of time, all on the surface of the Red Star. They use engines from the colonists ships to blow it out of orbit, very explosively.

Parallel to this, Oldive and Sharra develop an improved parasitic vector which is capable of infecting the space-born Ovoids that are the precursors to Thread, which is distributed on the Red Stars Surface by Greenriders and go on to infect the Ovoids still in the Oort-Cloud.

Later, in the turn 2538, the Dragonriders are forced to form a new craft, Starcrafting, where they protect Pens skies from comets and space debris, in order to appear still useful. Many Dragonriders begin to wish that Thread was still there, so that they would still have true purpose on Pern.

On OUR Pern, this never happens.

History of our Pern, 2520-2558.
In our version of events, when AVIS was discovered and offered a solution to thread, the dragonriders were not so enthusiastic. They knew that without thread, they would have no use. So they didnt tell the people of Pern that there was a possible solution and instead chose to tell AVIS to delete that piece of data from its memory.

They gleaned technology from AVIS, creating new Crafthalls. Not all survived to the present time though.

The new Crafts included DolphinCraft, PrintCraft, GeneCraft, SurgeryCraft (an advanced branch of HealerCraft), as well as major advances in all the current crafts. The new Genecrafters also revived species that the colonists had brought and either never unfroze or didn't survive the initial colonization.

With their advanced knowledge of the Planet and how it worked, there GeneCrafters were able to bring back species such as Deer, many small birds and many types of fish.

The DragonRiders of that Generation never told the next that they had been given the chance to have thread-free skies, so the knowledge died with them.

When the last of that Generation of DragonRiders was nearing Death, he went to AVIS, and told it not to give out any more knoledge. AVIS was almost completely shut down, with only a few ports being left operational, and those were transported to the new GeneHalls, where they were used to improve the current species and continue to experiment with the genes of new species, in hopes of bringing even more diversity to the Planet.