Amateur archaeologist Ben Bacon has discovered a primitive writing system used by Ice Age hunter-gatherers and concluded that the 20,000-year-old signs were a form of the lunar calendar, The Guardian writes. 

The study shows that the cave paintings were not only a form of artistic expression, but were also used to record complex information about the timing of animals' reproductive cycles.

Ben Bacon spent countless hours trying to decipher the proto-writing system, which is thought to predate other similar record-keeping systems by at least 10,000 years.

He approached a group of scientists with his theory, and they supported him.

Bacon collaborated with a team of scientists that included two professors from Durham University and one from University College London and published a paper in the Cambridge Archaeological Journal.

The results show that Ice Age hunter-gatherers were the first to use a systematic calendar and tags to record information about major ecological events within that calendar, explained Durham University archaeologist Professor Paul Pettit. 

Cave drawings of animal species such as reindeer, fish and now extinct cattle, aurochs and bison have been found throughout Europe. Along with these images, sequences of dots and other signs have been found in more than 600 Ice Age images on cave walls and portable objects throughout Europe. Archaeologists have long believed that these signs had significance, but no one has been able to decipher them.

Bacon set out to decipher them, turning to previous research and cave paintings in the British Library to find out what people were saying 20,000 years ago.

Using the birth cycles of equivalent animals today as a starting point, the team concluded that the number of tags associated with Ice Age animals was a record by lunar month of when they mated. 

The findings prompted the team to investigate further the meaning of other marks found on the cave drawings.