On the origin of the 12 zodiac constellation system in ancient Mesopotamia

This article pursues two main goals: (1) to reconstruct the history of the 12 zodiac constellation system in the astronomy of ancient Mesopotamia; (2) to reveal traces of this system directly in cuneiform texts. Among the most important circumstances led to appearance of this system: (1) development of ideas about the band of zodiac constellations, including—according to MUL.APIN—the total of 18 (or 17) constellations; (2) usage of the schematic year, containing 12 months, 30 days each, and (3) development of ideas about mathematical or uniform zodiac, subdivided into 12 equal parts, 30° each. A sequence of the so-called Normal stars singled out in the zodiacal band is an additional important source shedding light on the history of the Mesopotamian zodiac. The designations of Normal stars adopted in Astronomical diaries and other texts indicate that the system of 18 constellations was used in Mesopotamia until the end of cuneiform civilization. This means that in the second half of the first millennium BC the system of 18 constellations, adopted in MUL.APIN, and the system of 12 zodiacal constellations, borrowed from Babylonians by Greek astronomers, were used in parallel. It is also shown in the article that the system of 12 zodiac constellations was used in magical and astrological text BRM 4.20, dated back approximately to the last third of the fourth century BC.