with whatever cultural superstition they possessed built around that. Maybe the people and animal carvings are personifications of celestial objects, constellations and recurring events i.e. equinox's and solstice's and the like. People being able to predict earthly events by watching the sky was very important to hunter gatherer cultures because herd animals moved back and forth with the changing seasons and with the maturing wild grass seed and fruits ripened at certain times of the year and people could predict that stuff well in advance by watching the sky. Being able to predict those very important seasonal events gave people a huge advantage and allowed them to develop more advanced cultures.

They need to get an Archaeoastronomist on the case.