Physiology: a proper Luminai

Jarec's Ancestral Decree was established to maintain the purity of the Luminai bloodlines. (more) Two things are required to be considered a proper Luminai:

1.) An individual must be able to trace his lineage directly to Dominus. This has no direct correlation to percentages of Lumini blood versus human blood. It's all about bookkeeping, and the Luminai - especially following Jarec's Ancestral Decree - kept detailed records about this sort of thing in order to keep their pedigree pure. 2.) The individual must possess the physical/physiological traits of a Luminai.

While the first might be fairly easy to do, even for some Highborn who look entirely human, the second is a bit more complicated.

Which Luminai traits are required? The answer, of course, is "all of them." It isn't enough to be pale, or have funky-colored eyes, or have white hair, etc. An individual would need to be physically identifiable as a Luminai - such as Councilor Vaelen in Deradune, or the Governor in Auroria - right out of the gate. Their appearance must be undeniably Luminai, rather than merely cosmetic.

Source: Forums

1. Thinned blood

It's been several Luminai generations since Dominus came to Cassus, and the blood has thinned significantly in that time. Despite this, and likely due in no small part to Jarec's decree, it runs strongly in the current Luminai generation (such as with Myrcalus, whose lineage is so undeniable that he is referred to as "Dominus Reborn" by his subjects). It's possible that when the Eldan created the first Luminai, they introduced some interesting genetic modifications pertaining to the continuation of Luminai traits.

Source: Forums