From Warhammer 40k - Lexicanum
|Thule is put into orbit around the shipyards of Jupiter.
|Battle for the Abyss (Novel), Chapter One
|Powerful warp storms suddenly appear throughout the galaxy, making Warp travel all but impossible. Terra and its colonies are isolated from each other, destroying their interdependence. Worlds that relied on outside supplies suffer periods of anarchy and civil war, some even regressing to pre-industrial levels of technology. Standard Template Construct technology is largely lost. Hostile xenos such as the Orks begin to raid the now-vulnerable colonies. The isolation leads to divergent evolution of abhumans and psykers. Weak and inexperienced psykers suffer from daemonic possession, causing even more chaos and destruction. The Dark Age of Technology ends and the Age of Strife begins.
|Space Marine (Novel) [Needs Citation]
|The Horiax Treatise mentions genetic alteration techniques.
|Codex: Space Marines (3rd Edition), pg. 45. The Horus Heresy: Book One, pg. 26