Cave Carvings

One question that seems to fly all around the places, is that how can the same or similar type of rock cave carvings and figures seem to appear in multiple parts of the earth. 

Theory :

We can agree that one human can think of some idea, and ends up carving those ideas in a cave somewhere, randomly. Maybe another guy on the earth also does the same. But multiple people of multiple civilizations? When neither ships, nor railway, not planes, nor cars existed? How could multiple people across the continents know the same ideas and paint the same carvings, ever? Ancient Alien Scientists think it was someone who travelled across continents and spread the ideas. Possibly non earth entities.

Till today the purpose of those carvings is still not known, like for 100% accuracy.