Our ancestors looking into the night skies noticed that the firmament appears to spin about a fixed star. They did not know that the earth spins on its axis and that the Pole Star, or North Star sits directly above this axis and therefore appears motionless. Instead they conceived of an Axis Mundi stretching from a World Mountain on the earth up to the pole start around which everything else turned.
The Sumerians divided the heavens into three hundred and sixty segments to approximately match the number of days the sun took to complete a circuit of the heavens (i.e. from one solstice to another). Unlike us they didn't know that the earth orbits around the sun and that this causes the position of sunrise to shift about a degree each morning, until over the course of a year it has moved through the entire firmament, or the twelve constellations of the Zodiac. They conceived of the sun traveling through all the 'houses' of the Zodiac and assigned specific meanings to this. The decision to eventually divide the firmament into twelve was probably due to the fact that the Lunar Cycle is nearly thirty days and it therefore goes through twelve and a bit cycles in a year. Many cultures like the Egyptians used add a thirteenth month every few years to compensate for these extra days.
Our ancestors did not know that the earth is tilted on its axis and that except for the equinox days when the axis is exactly sideways to the sun, it is either orientated towards or away from the sun. This creates the four seasons in latitudes above or below the equator and causes the sun to rise at different points on the horizon ranging from the south-east at the winter solstice and to the north-east at the summer solstice.
With patient observation these cyclical patterns can be marked out using standing stones etc. However amid the above order our ancestors noticed that five celestial objects didn't move in tandem with the rest and appeared to follow more complex cycles. They did not know that these were the planets Mercury, Venus, Mars, Jupiter and Saturn which orbited our sun and psychologically projected onto them particular qualities and properties. The movements of these five, along with the sun and moon, were thereby accorded special significance and their cycles patiently observed. It is even argued that the perception by the Sumerians circa 5,500 years ago of an order in the firmament and the resultant conviction that life on earth should be put in 'accord' with these revelatory motions that facilated the decisive psychological leap to civilisation with all its attendant laws, arts and sciences. From this time onwards specialist skills within cities developed to support the seasonal ritual calendar associated with a priest-king, a priesthood and a court. The surplus produce of farmers hence forth found use in provisioning an elect group dedicated to the weighty task of ensuring concord between heaven and earth.