The earliest form of writing we've ever found is embedded in 20,000-year-old cave paintings according to researchers.
The symbols on the walls are believed to have been used by hunters from the Upper Palaeolithic era.
It pushes back the earliest form of writing by over a thousand years.
The researchers wrote in their paper that the markings represent a complete unit of meaning.
The team looked at hundreds of dots, lines, and Y shapes found in cave paintings.
The process of decoding them needed to be next to the animals.
The meaning of the markings within these drawings has always intrigued me, so I set about trying to decode them, using a similar approach that others took to understanding an early form of Greek text.
The hidden meanings of these marks were revealed when the database of painting samples was compared against the birth cycles of equivalent animals.
It was thought that the Y symbol in these paintings stood for 'giving birth', and that the people of the time needed vital information about these animals.
Even if the calendar system that they applied here has since fallen out of use, these Ice Age hunters were still making records of past events to help them in the future.
The lunar calendar doesn't fit neatly into a year because there are just under twelve and a half lunar months in a year.
Our own modern calendar has lost any connection to actual lunar months.
Not everyone is convinced by the conclusion that we're looking at a mating season calendar here or in a form of what you could call writing, and the work outlined by these researchers does involve some degree of interpretation and guessing.
According to the researchers behind the new study, these markings are an intermediate step between simpler and complete writing systems. The idea is worth further investigation and study.
Basic pictographic shapes became the basis of writing in Mesopotamia around 3,300 BC. The history of scrawling on stone may go further.
The study shows that Ice Age hunter-gatherers used a systematic calendar and marks to record important ecological events.
The people who left a legacy of spectacular art in the caves of Lascaux and Altamira also left a record of early timekeeping.
The research is in a journal.