Some ancient cave paintings assumed to be animal symbols actually represent star constellations, scientists say.
New research suggests humans had a sophisticated knowledge of the stars as long as 40,000 years ago.
They also appear to have kept track of time by watching how stars slowly change their position in the night sky.
The phenomenon, known as precession of the equinoxes, is caused by the gradual shift of Earth's rotational axis.
Its discovery was previously credited to the ancient Greeks thousands of years later.
The cave artists looked to the stars to mark major events such as comet strikes, according to the researchers.
"Early cave art shows that people had advanced knowledge of the night sky within the last ice age. Intellectually, they were hardly any different to us today," Study leader Dr Martin Sweatman, from the University of Edinburgh, said.
Teams from the universities of Edinburgh and Kent studied details of Palaeolithic and Neolithic cave art sites in Turkey, Spain, France and Germany.
Animal symbol pictures daubed on the walls of the caves were aged by chemically dating the paints used.
Computer software was then employed to predict the positions of stars when the paintings were made.
The results showed that what looked like abstract depictions of animals could be interpreted as zodiac signs based on constellations as they appeared at the time.
At every site, the cave artists practiced a method of time keeping based on astronomy, the scientists claimed.
This was despite the fact that the paintings were separated in time by tens of thousands of years.
The world's oldest sculpture, the Lion Man of Hohlenstein-Stadel cave in Germany, an ivory carving almost 40,000 years old, was also found to support the zodiac symbol theory.
Writing in Athens Journal of History, the researchers described how an ancient carved stone pillar from Gobekli Tepe in Turkey provided them with their "Rosetta Stone" – the key to unlocking the zodiac code.
It was thought to commemorate a devastating meteor impact in North America 11,000 years ago that led to the Younger Dryas Event, a period of sudden climate cooling that triggered a mini-ice age across the northern hemisphere.