There is no strong proof that the early man wear tree barks, leaves, and animal skin. In history, we have studied that, the early man firstly live without clothes. Later on, with the passage of time, their brains started developing, they learn how to cover and protect their body from different climates and insects with tree barks and leaves. Then they started hunting animals and use their skin for covering their bodies.
Then they learn to make clothes. As tree barks, leaves and animal skin are decaying items.So, there is no proof from ancient time..but if anybody wants to know that how ancient people cover their bodies with all these decaying items he/she can search for the living style of African people who still cover their bodies with all these items.. that can be helpful to study how ancient people live..This can also be a proof for us that how our ancestors live and survive with all these items..