I have just been visiting the limestone karst caves of Northern Spain for their Palaeolithic paintings. The most famous is the Altamira Cave discovered near Santillana del Mar in 1868 and first explored properly in 1880. The oldest drawings are dated ca 35,000 years old, the renowned bison paintings to ca 13,500 years old.
Basically, the early Homo sapiens were sheltering and living in that cave and decorating it for a continuous period of over 20,000 years. Something like a thousand generations. That makes Roman settlements seem a bit like yesterday.
It wasn’t until ca 1900 that scientists accepted these were prehistoric and subsequently advanced dating methods proved that. There will be more to discover as some of the caves were only found in the 1970s and later. The paintings that have survived well are those where the entrance collapsed thousands of years ago and preserved the environment inside.