How do you make a Space Marine (Astartes)?

Warhammer is famous 1 thing more than any other. Space marines. The God Emperor of mankind’s avenging angels.

What is less well known is how you get an astartes unless you follow lore channels on Youtube or have an existing interest in Warhammer 40K. This situation is one of the reasons warhammer is seen as grimdark. How you go from a mundane human child to a over 2 meter tall death machine.

Unfortunately that is how it works. The Space marine chapter has a selection trial of some kind. This is how they choose their aspirants. These are the as young as 10 year old children who could become astartes. They must pass the selection trial which is often incredibly difficult with a very tiny chance of success.

The aspirant once chosen will become a neophyte. A neophyte is someone who is still an adolescent and will begin to receive the implants. These implants are archeotech or technology form before the empire of mankind experienced a civil war.

Each implant is derived from the gene seed of a veteran or fallen battle brother of the chapter. It is from the chapters primarch and so carries a range fo bugs, defects and anomalies.

There are 19 gene seed implants:

Secondary heart
Ossmodula
Biscopea
Haemastamen
Larraman’s organ
Catalepsean node
Preomnor
Omophagea
Multi lung
Occulobe
Lyman’s ear
Sus-an membrane
Melanochrome
Oolitic kidney
neuroglottis
Mucranoid
Betcher’s gland
Progenoids
Carapace

Each implant involves highly invasive surgery that puts organoids into the body the neophyte. Each ha sit role to play int the development of the neophyte into a astartes. Even the apothecary and magus biologus are not entirely clear on how to make some of these organs any more.

This is why they rely on harvesting gene seed from the chapters members. That also introduces a error margin. More accurately an error rate as it is not marginal. The death rate among neophyte recipients is appalling.

This is all down to lack of knowledge. It is also why we believe some of the information as presented is wrong. Not through malice but ignorance. It is the best explanation for something barely understood if at all.

That is why along with explaining what each organ does we explain how it would work and what it would take to make it functional. Not necessarily entirely functional or exactly as written in the lore but as close as is possible based on modern understanding of biology, physiology and anatomy.

Some things need considerable interpretation while others are fairly clear cut. Than ther eis everything in between. As a result there is a range of understanding in this video.

We clearly identify the proposed lore of the organoid and than how we think it might actually be done or work. Fortunately the authors at GW are not exceptionally creative so we are able to apply our knowledge to a limited set of facts.

We also discuss why the age of the neophyte is key. The hormonal changes needed and how the implants interact with existing body structures to get the results described.

Relevant links:

Gene-Seed
https://warhammer40k.fandom.com/wiki/Gene-Seed

Muscle hypertrophy and pseudohypertrophy
https://pn.bmj.com/content/17/5/369

Wikipedia: scar
https://en.wikipedia.org/wiki/Scar

Wikipedia: Fish gill
https://en.wikipedia.org/wiki/Fish_gill

Wikipedia: photoreceptor cell
https://en.wikipedia.org/wiki/Photoreceptor_cell