|The following is based on Fallout 3 cut content and has not been confirmed by canon sources.|
In my seven dozen years studying the ghoul anatomy, I discover more and more evidence to support my theory on the nature of the not-radiological human, or "ghoul" as they are commonly called.
In summary: I theorize that our unnaturally long lifespan is due to a mutation within the autonomic nervous system of certain individuals following exposure to specific combinations of ionizing radiation with wavelengths below 10 picometers. This mutation, it seems, disrupts the normal process of decay in the neurotransmitters along the spinal cord.
Specifically, the transmitters effected are those responsible for cardiac and respiratory function in a healthy human. According to my studies, these transmitters are continually regenerated after mutation, carrying sufficient oxygen to sustain the life of the subject while being insufficient to retain skin elasticity and avoid necrosis, the result of which is the corpse-like appearance of post-mutation humans. It should be noted that exposure to radiation typically result in sickness followed by death and the x-factor that will lead to mutation upon exposure in lieu of the typical outcome remains unknown to this researcher.
In the coming months, I will be assembling my findings on this subject into a full study.