A Question of Loyalty

[Pitchwife]

Originally Posted by Morthoron

Hmmm...if I remember correctly, Tolkien originally envisaged Orcs as physical manifestations of Maiaric spirits won over by Morgoth (this, of course, was before the corrupted elves concept or twisted mortal men idea came into effect).

Other way round, actually, if I'm not mistaken. 'Originally' (i.e. in BoLT and the early 1920s or thereabouts) Morgoth 'brought forth' the Orcs in some unspecified way. Later Tolkien decided that evil couldn't create and came up with the idea that Orcs were corrupted Elves (as in the published Silmarillion). Much later still (in Myths Transformed) he changed his mind again and experimented with the idea that Orcs were twisted Men and/or (at least in the case of some formidable chieftains) Maiar.
Anyway - if Orcs = corrupted Elves, they should be immortal; if (some) Orcs = Maiar, too.

However, most of the indications in Lord of the Rings is that Orcs were, at least in the 3rd Age, bred from mannish stock.

Nope. As far as we know, only Saruman ever cross-bred Men and Orcs; otherwise the Orcs multiplied like the Children of Ilúvatar, i.e. took care of their own breeding without need for special intervention.
But as this is only a side-topic and doesn't contribute to this thread in general, I'll shut up now.