I defend that comparison elsewhere (links below). I rely mainly on a narrow, objective sense of childishness, based on the impossibility of reliable accumulation of collective knowledge before the invention of writing. And I build on David Graeber's point that prehistoric people were more experimental (playful) in their social organizations.

https://medium.com/history-of-yesterday/were-prehistoric-people-childlike-b688bc6dcacd?sk=bfd05b650b87855d6b589dc39e6afb43

https://medium.com/grim-tidings/do-all-cultures-start-from-childish-twaddle-6a7cf341d066?sk=0340a347f82ad7b501edf9d01f37bae6