The earliest channel texts recovered from Mawangdui prescribe cauterisation for every condition they describe and never mention inserting a needle. Moxibustion is therefore the older of the two techniques, and the classical statement that moxibustion came from the north while the nine needles came from the south preserves a memory of their separate origins.
The subsequent history is one of gradual substitution. Needling became the more prestigious technique, moxibustion the safer one, and the two were combined in practice rather than opposed. The Guan Neng chapter of the Ling Shu already treats them as complementary, and the Tang compilers who distrusted the needle turned back to moxibustion for exactly that reason.