In the beginning Mesopotamian astrology was much like that of other cultures, a simple examination of the heavens for omens that might affect the kingdom. Often these observations of omens would include weather phenomena intermixed with true astronomical ones. What made the Mesopotamians different is that they began at an early time to make systematic observations of phenomena with an eye to finding regular patterns in the heavens that might correlate with patterns in human events.
According to Van der Waerden (Science Awakening, Vol. II, Oxford Univ. Press) the earliest astronomical writings known in Mesopotamia are from the old Babylonian period, roughly the time of Hammurabi. It is not known whether the Sumerians were involved in astronomical studies or not, but it would seem plausible that they were. There are also some writings which refer to the Akkadian period and which may date from about 2300 B.C.E. Here is an example of one of these early writings.
The most extensive omen lore was contained in a compilation referred to as Enuma Anu Enlil. These were assembled somewhere in the second millennium B.C.E. Another collection of omens is an important work, the dating of which is extremely controversial, the Venus Tables of Ammizaduga. This consists of systematic observations of the phases of Venus combined with their omen significations, the significations being clearly based on past observations. The general belief is that these tables date from the reign of Ammizaduga about 146 years after Hammurabi. Based on the astronomy, van der Waerden assigns the following years as possible dates for the observations, 1702, 1646, 1638, and 1582 B.C.E. One of the reasons that these dates have become controversial in certain circles is that if these dates are correct, then Velikovsky is seriously in error. That controversy is outside of this scope of this introduction however, and we will continue on the assumption that orthodox scholarship is at least reasonably correct. Still I urge readers to take the dates with extreme caution. The Babylonians themselves, much like modern Hindus, attributed an antiquity to themselves and their observations that seems fantastic by modern Western standards, hundreds of thousands, even millions of years. Such antiquity is not consistent with the evidence of scholarship, but we have to keep something of an open mind. Scholars are often limited by their very specialization with the result that one discipline, such as modern astronomy for example, may often have powerful consequences for another such as archeology. The work of Gerald Hawkins on Stonehenge comes to mind. But first someone has to bring the two disciplines together. This may yet happen in Mesopotamian studies in such a way as to radically alter our historical understanding.
Van der Waerden concludes that the Venus tables were compiled and preserved out of motives of astral religion, i.e., the Mesopotamians believed that the stars and planets were associated with, or were in fact themselves the gods. Ishtar-Venus was one of the major divinities of the Mesopotamian peoples. Many other ancient peoples had similar notions. The Egyptians identified the constellation of Orion with Osiris. But Osiris was a dead god who ruled the underworld. His transportation to the heavens was very similar to other transportations made in classical mythology. The Mesopotamians seem to have been unique in their emphasis on the stars and planets as being the primary indicators of divine will in the Here and Now. This is the probable motive of the studies that led to astrology.
Over the next centuries the Mesopotamians, especially the Babylonians, continued observing and compiling lists of phenomena eventually getting to the point where, based on observed recurrence cycles of the planets, they could reasonably accurately estimate the positions of the planets at any time in the future. Ptolemy records, and modern scholarship does not dispute this, that accurate and systematic eclipse records were kept from 747 B.C.E. onward into the Hellenistic period after the conquests of Alexander the Great.
An interesting question about which there is much controversy is what kind of zodiac were the Mesopotamians using? In the earlier material they simply recorded planets as being so many degrees from a star.
This is de facto a sidereal observation, but it is not a zodiac! A zodiac requires a fiducial point, a point on the circle from which measurements are made. Also normally a zodiac has some fixed number of regular divisions such as the twelve signs of the modern zodiacs, the twenty-seven lunar mansions of the Hindu lunar zodiac and so forth. But all of these early observations are like this one in using individual stars as markers for positions.
Van der Waerden argues that the evolution of astrology went through three phases. The first phase consists of the omen lore that we have already described. The second phase is closely related to this but has a zodiac in the modern sense, twelve 30 degree signs. There is no personal horoscopy in this middle level, but great attention is paid to the transits of Jupiter through the signs at the rate of approximately one sign per year. From this is clearly descended the Chinese practice of assigning each year to a zodiacal sign, and probably also the system of annual profections in later horoscopic astrology. There are also of course no houses of any kind. Van der Waerden dates this middle phase as being from about 630 to 450 B.C.E.
The zodiac at this point is clearly a sidereal one and its ayanamsha is at least close to the Fagan-Allen value.
The third phase is horoscopic astrology. Various ancient sources mention "Chaldeans" who cast birthcharts for various persons, including Diogenes Laertius who said that according to Aristotle, a Chaldean forecast Socrates's death from his birthchart, and that Euripides' father also had his son's chart read getting a forecast of his brilliant career. The reference to Chaldeans of course refers to astrologers and makes it clear that the art in this period was completely associated with late Babylonians, i.e., Chaldeans.
Several birthcharts have been found written in cuneiform. Most of them date from well within the Hellenistic era, but the oldest has been dated by A. Sachs to April 29, 410 B.C. Here is the translation as given by Fagan.
As the reader can see this is a very rough chart with only sign positions given, and no delineations at all. The other cuneiform charts, though much later, are almost as terse, although positions are given to much greater precision.
As Cyril Fagan correctly points out, the positions in the charts also correspond more nearly to those of the sidereal zodiac using the Fagan-Allen ayanamsha than to tropical positions.
But do we have at this point anything like the elaborate horoscopic astrology of the later Hellenistic era? No we do not! Although academic historians have not uncovered much concrete information about the evolution of astrology after the early Babylonian charts, there is considerable internal evidence for the place of origin in the earliest texts. Many of these old texts are contained within this volume (refering to the Project Hindsight volume). According to these texts the birthplace of astrology as we know it is Egypt.
This would not have been a surprise to Cyril Fagan. He maintained almost alone that Egypt had been the birthplace of horoscopic astrology. The trouble with his theory however is that he believed that horoscopic astrology came into being in the Egypt of the pharaohs. For this there is very little evidence outside of Fagan's own somewhat questionable interpretations of the evidence. It was a later Egypt that gave birth to horoscopic astrology, an Egypt that had made close contact with the ideas of the Babylonians.
Pharaonic Egypt had a great interest in astronomy. This is evident in too many ways to mention. But it was the kind of astronomy that involved stars rather than planets. The Egyptians were masters of aligning buildings, temples and especially the pyramids to fixed stars, apparently in an effort to bring about sympathy between terrestrial structures and the stars with which they were associated.
Their ability to survey and align buildings with stars was incredibly accurate, often within minutes of arc of the perfect alignment. But they do not seem to have had any planetary theory, nor did they have the proper mathematical techniques.
The Mesopotamians inherited the sexagesimal system of numbers from the Sumerians, a system which used place notation in numbers much like our modern decimal system, and which had sexagesimal fractions very similar in kind to our decimal fractions. This enabled the Mesopotamians to do complex computations that would have been difficult in any other ancient system of numerical notation. The other ancient peoples paid Mesopotamian mathematical notation the supreme compliment. They used it whenever they had to do similar calculations of their own. The Egyptians had nothing like it. But they did have a strong sense of a need for terrestrial matters to be brought into synchrony with the heavens.
The critical factors in the fusion of Egyptian ideas with Babylonian astronomy was one or both of two historical events, the conquest of Egypt by Persia, and the conquest of both Persia and Egypt by Alexander the Great. On both of these occasions Egypt was brought under the same regime as the Babylonians. In the case of the Persian Empire, the Persians themselves became ardent devotees of astrology which no doubt assisted the movement of astrological ideas into Egypt.
And if you were to examine the texts included in the volume on the Sages, you would discover something that is not all obvious from history texts that deal with astrology. The ancients clearly knew that astrology had something to do with Babylon (after all they did call astrologers Chaldeans) but the principle credit was given to the Egyptians. It is customary among academics to pass this off as something that was merely a fashion among ancient writers with no real historical basis. And in fact the ancient writers did often attribute astrology to persons dating back to the pharaohs such as Nechepso and Petosiris. Nevertheless, there is no reason to assume that the ancients were not correct as to Egypt's being the primary source of horoscopic astrology; it was just somewhat later than they supposed.