here's my theory. ghouls are humans who were, like all creatures, exposed to small concetrations of FEV in years after the nuclear war. however, extreme radiaton levels have caused the FEV to alter DNA of these humans incorrectly. in their case, the forced evolution to quad-helix DNA incomplete, which is why many of the cells were destroyed and consequentially severe damage to tissue was dealt. muscle tissue was impacted most, which is why ghouls are weaker than humans. all haploid cells were destroyed by FEV, which is why ghouls are sterile. due to small concentration of FEV in the atmosphere, it didn't significantly affect the nervous system, which is why ghouls have intellectual capabilities of normal humans. most of the ghoul cells that weren't destroyed by effects of FEV have gained increased regenerational abilities, so ghouls heal faster and are generally more endurant and resistant than normal humans. with time they restored great deal of their muscle mass, so many ghouls are now quite strong, but their skin was completely burnt by radiation and it couldn't regenerate. the regenerative abilities give them prolonged life, but that's far from virtual immortality granted to most powerful and successful supermutants. it is obvious that ghouls are in fact super-mutants who didn't turn out very super. "dumb" supermutants contained a certain level of radiation in their bodies, which is why some of their tissues, particularly the sensitive and complex neural tissue, failed to evolve properly after exposure to FEV. ghouls, on the other hand, were exposed to much greater radiation levels and much smaller FEV concentrations than Master-made supermutants, so they the virus failed to evolve them properly all together, leaving some tissues intact, others terribly impaired and only some successfully transformed to quad-helix DNA and therefore with "useful" properties such as regeneration and immunity to retroviruses and similar agents which work by changing the DNA of the infected cell.
there, i hope my theory sounds acceptable. i had to invent a lot of bullshit, but now it makes more sense (for me, at least) than explanations offered by Fallout Bible. flame me if you like, but i'm stickin' with this one
i still haven't found a good explanation for what happened to Harold. if he fell into an FEV vat, then he must have been exposed to extreme FEV concentration. my theory is that he was still conscious enough to pull himself out of the vat and flee the base. then he most likely passed out in the desert, probably due to effects of FEV. FEV also affected his memory, which is why he doesn't remember climbing out of the vat and leaving the base. because he was only exposed to FEV briefly and was already badly radiated after many years spent in the wasteland, he didn't evolve properly and instead became a ghoul. as for his skin, the description in Gecko says he is a "particularly leathery ghoul". this confirms one of my assumptions: FEV doesn't cause loss of skin - ghouls lost their skin when they were human, due to radiation. reason why Harold's skin is in such bad state are horrible sunburns. remember, Harold spent several days lying helpless and motionless under the hot desert sun before he was rescued by a caravan and brought back to Hub. any dermathologist will tell you that burns caused by sun roasting you for several days at 45 degrees Celzius cannot heal...ever.
