The Emperor was in his most secret laboratory, a place even Erda, who had worked with him on the Primarch project, had never set foot in.
Erda's exceptionally unique and important genetic sequences had been extracted, tested, and applied.
The Emperor's own genetic sequences had been added as well.
As he carried out procedures shocking enough to astonish even human biologists of the Golden Age, the Emperor suddenly thought of a unique, yet not entirely unique, genetic sequence he had seen before.
The genes of that primitive human who possessed the power of the C'tan.
In the early days of humanity's entry into the space age, after conquering certain xenos civilizations, humanity established rule over their homeworlds.
The ruling class was bound tightly together by genes and race, rather than class, wealth, or property.
Those xenos homeworlds had contingency plans: genetic weapons capable of exterminating a specific xenos species; archives and armories accessible only to humans, established so that enslaved humans would not forget who they were should the xenos seize power. These things scanned the user's genes. Regardless of the user's purpose, it first had to be ensured that the user was human.
At that time, human genes had not yet diverged as vastly from primitive human genes as they had in the Golden Age, and genetic technology had not yet seen widespread application.
Yet the legacy that those primitive human genes might unlock, relics from humanity's earliest days among the stars, made even the technological products of humanity's current age of ignorance seem like children's toys. Like the primitive humans' genes themselves, their existence was their sole value, much like the human artworks in Malcador's possession.
Humanity had forgotten too much over its long development, even itself.
The genes of Perpetuals were naturally different from those of primitive