According to a recent paper, 20,000-year-old cave art is not just art, but a sophisticated method of recording the timing of animals’ reproductive cycles based on a lunar calendar. Alongside images of aurochs, reindeer, fish, bison, and other animals in caves like Lascaux and Altamira are strange dots, lines, and other marks. At least 600 such images have been documented across Europe. According to the researchers, the number of marks acted as a record of which lunar month an animal mated in. And a “Y” sign meant “birth”. If correct, this pushes back this type of record system by more than 10,000 years. According to Paul Pettitt, “The results show that ice age hunter-gatherers were the first to use a systemic calendar and marks to record information about major ecological events within that calendar.” I love this for so many reasons, not the least of which is that an amateur discovered it, then worked alongside academics.