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How did Babylonian diviners begin using planetary positions to predict an individual's life?

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What's your sign? — astrology Zodiac wheel showing the 12 astrological constellations or signs from an illumination of the poem *Breviari d'Amour*, Catalan (Spain), late 14th century; in the collection of the British Library.

In the 3rd century BCE, or perhaps slightly earlier, Babylonian diviners began utilizing planetary omens to predict the course of an individual's life. They achieved this by observing specific planetary positions and motions at the moment of a person's birth or computed conception.1

These observations included:
* Positions relative to the horizon1
* Latitudes1
* Retrogressions1

While this practice was distinct from the later, more formal system of casting birth charts (genethlialogy), it evolved in parallel with those developments in Hellenistic Egypt. This shift marked a transition from earlier Mesopotamian traditions, where celestial omens were primarily intended to warn the king and kingdom of events like war or famine, toward a focus on personal astrology.12