Editing Gene-seed (section)

== The Tithe and New Foundings ==

As part of the deal in Guilliman's [[Codex Astartes]], the Astartes were afforded almost complete autonomy from the [[Administratum]], which means they don't have to pay Imperial Taxes '''except''' for a tithe of 5% of their gene-seed which they must send to Mars.

This has a few important purposes:
# To monitor the genetic purity of the Space Marine Chapter as a whole and make certain a chapter is not suffering heretical mutations.
# To create new foundings of Space Marines whenever the High Lords of Terra deem it appropriate to do so.
# To act as an emergency reserve of gene-seed in the unlikely event that the Chapter's existing gene-seed stocks are lost or tainted.

Note that even though the Adeptus Mechanicum will have stockpiles of a chapter's genetic material, it is not frequently used as a contingency for a space marine chapter if things get a bit hairy. Several times in the fluff a Chapter has faced extinction due to high losses ''(see [[Black Consuls]], [[Celestial Lions]], [[Lamenters]], [[Marines Errant]], [[Scythes of the Emperor]] yadda yadda yadda)'' but they'd never thought to ask Mars for their gene-seed back. The only known instance of it happening is in the 8th Edition Death Guard Codex, where the [[Minotaurs]] were forced to undergo a mission to Mars when a Death Guard assault on their fortress-monastery resulted in the poisoning of their gene-seed stocks, but the Minotuars are basically the High Lords personal beat stick against other marines so perhaps this is special treatment.

It's also a bit uncertain how chapters with particularly negative defects manage to keep their genetic condition concealed, if the government has access to their core materials. [[Black Dragons|Some chapters]] get around it by sending only the "purest" gene-seed to Mars and so come out of the inspection smelling of roses, but when the condition is widespread (as it is with the [[Blood Angels]]) it probably only highlights how little the Mechanicus actually understand about the Emperor's work. (Things might perhaps change now that [[Belisarius Cawl|Cawl]] is back, though.)

It's also important to note that each chapter's gene-seed is kept in isolation. i.e: Just because a chapter claims ''descent'' from the [[Ultramarines]] does not actually make their gene-seed the same as their forefather. It's basic evolutionary biology that when a population splits and develops elsewhere it starts forming its own traits advantageous to its circumstances and environment. Hence the [[Mortifactors]] gene-seed will largely be very different from the [[Howling Griffons]], despite sharing a common ancestor. So rather than being genetic "brothers" as they would be ''within'' a chapter, different Space Marine chapters sharing a lineage would be more like nephews or cousins.

When the time comes around to found new chapters, the adepts will look for favourable traits that they want to replicate, although the Ultramarines are cited as being the most utilised source for new foundings, thus any new chapter of Ultramarine descendants would likely be second generation Ultramarines and be quite close to their forefather genetically at least until the chapter adapted to its founding homeworld or particular circumstances. But that doesn't prevent those descendants themselves from being used as templates in later foundings, so after several generations you could end up with something completely different from the original baseline stock.