When Christopher Tolkien began publishing The History of Middle-earth, a twelve-volume series documenting J. R. R. Tolkien's writing process in the creation of Middle-earth, with texts dating from the 1910s to the 1990s, he made a conscious decision not to issue a volume detailing the creation of The Hobbit. According to him, The Hobbit was not originally a part of the Middle-earth universe and was attached to his father's earlier, far darker legendarium only superficially, although the existence of The Hobbit forever altered the legendarium.