Why do space marines value their gene-seed surviving?

Question

In several books I've read recently an emphasis is put on saving the gene-seed of specific individuals.

In Soul Hunter, Talos comments about possibly not saving the gene-seed of specific brothers seemingly because he does not like them personally.

In Pharos chapter 12, Sgt Arkus tells the scouts that they must retreat because "it is your role to ensure the gene-seed of your predecessors lives on".

I understand the value of the gene-seed to create new transhuman Astartes, but why would any specific Astartes care once they're dead if their gene-seed continues or not?

Answer 1

It is in a bit in the same way, that you would care that your children would live.

[..]cells grow and are stored in the Progenoid organs, much like sperm cells or egg cells are stored in the testes and ovaries of normal men and women. When properly cultured by the Apothecaries of a Space Marine Chapter, these germ cells can be gestated into each of the 19 gene-seed organs needed to create a new Space Marine. Thus, for most Astartes, their Progenoid Glands represent the only form of reproduction they will ever know, though the DNA passed on will be that of their Primarch, not their own.

For Astartes, the gene-seed is almost sacred and the more powerful was the original owner, the more valuable it is, hence often you can find stories where whole squads were fighting to reach and evacuate the progenoid glands of a fallen hero - good example you can see in the "Soulstorm" game, when you capture the Space Marine final base, a group of Marines stays behind just so the dead body of their captain can be evacuated.

I don't think that I've ever found a proof that such gene-seed would be in any way better than one from a regular Marine, but Astartes seem to believe that it is.

Answer 2

The Adeptus Astartes engineered the gene-seed technology at the First Founding of the 30th millenium, and since that time the technology to engineer new gene-seed or even implant Astartes organs has been lost. The rampant mutations of the gene-seed has caused a depletion in the supply of stable genetic material for culturing all 19 implants. Essentially, these factors mean space marine gene-seed is no longer a renewable resource and they must do everything possible to preserve it.

Now also consider that at the First Founding 20 different space marine legions were created, but each legion developed their own gene-seed technology independently. As a result, the gene-seeds were not intercompatible. Each type of gene-seed required a unique ritual to create a transhuman Antares. For example, the Blood Angels required the rite of Insanguination, while the Imperial Fists required the Hand of Faith. Thus just having a gene-seed was not enough, you had to have the right ritual for the right gene-seed.

This is why the gene-seed of each transhuman Astartes is vital, and for certain legions whose numbers are dwindling, those Astartes' gene-seed must be preserved at all cost. Once one legion is lost, it is lost forever. And if their numbers get too low to fight, well, game over.

Some Astartes have a more stable gene-seed than others, and this may be the case with the captain you are referring to. Specifically, the Primaris Space Marines' gene-seed has a mere .001% chance for suffering a genetic deviation between generations and can sustain even ionizing radiation much better than typical gene-seed. These Primaris Space Marines are also highly protected, as their gene-seed was derived directly from the Primarch.

Most of this is available on the Wikia page if you want more info.

Answer 3

Gene-seeds represent the past, present and future of the Chapter. An especially heroic Marines gene-seed would be valued above all others.

A gene-seed represents the cumulative past of the Chapter, possibly all the way back to the founding the the Chapters parent Legion. Also to the current Space Marine it is embedded in, the future of the Chapter too.

When an especially heroic Marine dies, it's very important to the Chapter that his gene-seed is harvested, so some part of the Marine can live on in the Chapter. Hopefully producing similarly impressive Marines in the future.

I believe each gene-seed absorbs some traits from the Marine it is embedded in and in turn passes them on to the next human it is embedded in. If a Marine is particularly skilled swordsman, it's very likely his direct successor will be also. It's the same as Space Wolves gene-seeds passing on the Wulfen mutation. You have to take the good with the bad!