I don't know much about the tribal and more primitive way of living but I do know people who live in very cold climates their bodies will develop a resistance to colder temperatures so often times they don't need to layer themselves with multiple clothes.( ̄∇ ̄")
My only guess is since he has obviously been living their since his birth he probably is accustomed to the changes in temperatures and doesn't need to and or feel the need to wear more clothes.(⊙…⊙ )
But I like you I do think he could wear at a little more clothes for protection I mean if they are in the jungle what about the bugs!? Σ(っ°Д °;)っ

I-I just wanna ask, does his dingdong ever feel cold? I mean, they are in a jungle with thin clothes so uhm... I'm just concern okay? Jwbzhsjanwn!! Please put more clothes!!