Not being an anthropologist I picked up on the article repeatedly saying homo naledi wasn't a direct descendent of ours and had a brain half the size of a moder

Not being an anthropologist I picked up on the article repeatedly saying homo naledi wasn't a direct descendent of ours and had a brain half the size of a modern chimp - which leads me to wonder are we missing the funerary behaviors of the Great Apes? Do we really know the other Great Apes as well as we think we do? If we do, then why did their funerary behavior evolve to be so different?