The animals being around much longer, was wiser and stronger then the humans, and often had to teach them how to survive in the wilderness.
Rhino had the knowledge of how to make fire.
Otter had the knowledge how to catch fish and swim, and the Baboon had the knowledge of which wild fruits and plants to eat.
The Otter and Baboon was quite happy to share their knowledge with the San, but Rhino being a grumpy and bad tempered old fellow, refused to share his fire knowledge with the humans.
Every time the humans ask Rhino, “Please teach us how to make fire, as we get cold at night and the dark night is scary.” Rhino will just snort through his nose and storm away shouting, “I do not know, go away!”
But every time Rhino told this lie, his mighty horn on his nose start to itch terrible.
Having no hands to scratch, he would use a tree to rub his itching horn against, only to set the tree on fire. Many, many times the humans asked Rhino, and every time the same thing happened.
So, over a long time, the grey ashes of all the burning trees has stained Rhino’s hide to a grey colour and made his eye sight very weak.
So much so, even today when you see a Rhino, his skin is still grey.
Because the Rhino did not share his knowledge, the San had to stole the fire secret from him, but that is another story on its own.