This article is from the Tolkien Newsgroups FAQ, by Steuard Jensen sbjensen@midway.uchicago.edu with numerous contributions by others.
[This updates question V.G.1 of the Tolkien LessFAQ.]
Tolkien never seems to have firmly resolved this question in his own
mind, let alone on paper. While _The Silmarillion_ as published states
fairly clearly that Orcs were corrupted Elves, _Unfinished Tales_ hints
that some strains of Orcs may have been bred from the Druedain.
Tolkien's latest writings on the issue (found in Texts VIII-X of the
"Myths Transformed" section in _Morgoth's Ring_) show him considering
many possible origins: corrupted Elves, corrupted Men, very minor Maiar
(a small number of original Orcish leaders only), or even beasts given
fragments of Morgoth's own will so they would have some measure of
independence. Some combination of these origins seems most likely from
the texts, though the last of them was probably rejected.
All of these suggested origins still support the notion that Orcs
reproduced in the same manner as other races (and therefore that there
were female Orcs). This is explicitly discussed in Text X of "Myths
Transformed", which states that
Men could under the domination of Morgoth or his agents in a few
generations be reduced almost to the Orc-level of mind and habits;
and then they would or could be made to mate with Orcs, producing
new breeds, often larger and more cunning.
The role of female Orcs in their society is not at all clear.
 
Continue to: