Orcs... were elves?

[Inziladun]

More food for thought on this topic.

I'm leaning toward the idea that "specialist" Orc-breeds might have been partly derived from the blood of Men, but I'm nearly positive Elves were the foundation of the "basic" Orc.

In addition to things already said above in this thread and others, I note that Elves were from their beginning immune from disease.

Immortal were the Elves, and their wisdom waxed from age to age, and no sickness nor pestilence brought death to them.

Silm Of Men

I think it's reasonable that Morgoth would have known that about the Elves. After all, he was a Vala.

Now, deliberate disease infection was used by Morgoth in the First Age, I believe, as a "terror weapon" against the Men of northern Beleriand. One of the casualties was Túrin's sister, Urwen, called Lalaith.

....when [Lalaith] was three years old there came a pestilence to Hithlum, borne on an evil wind out of Angband, and she died.

Silm Of Túrin Tarambar

The large uruks with possible Mannish blood don't seem to have been around in the First Age, so I'm thinking that Morgoth's Orcs were from whatever the original stock had been. If that stock was indeed Elves, they should have been immune from disease, and Morgoth would have run no risk of infecting his own troops and possibly decimating his own forces by the plague. Especially when it doesn't seem to have really been necessary in a strategic sense.