With man it is different. When he comes many of the larger animals instinctively leave the district entirely, seldom if ever to return; and thus it h… - Edgar Rice Burroughs

All he knew was that he could not eat the flesh of this black man, and thus hereditary instinct, ages old, usurped the functions of his untaught mind and saved him from transgressing a worldwide law of whose very existence he was ignorant.

Miss La Rue was very quiet, though she replied graciously enough to whatever I had to say that required reply. I asked her if she did not feel well.
“Yes,” she said, “but I am depressed by the awfulness of it all. I feel of so little consequence—so small and helpless in the face of all these myriad manifestations of life stripped to the bone of its savagery and brutality. I realize as never before how cheap and valueless a thing is life. Life seems a joke, a cruel, grim joke. You are a laughable incident or a terrifying one as you happen to be less powerful or more powerful than some other form of life which crosses your path; but as a rule you are of no moment whatsoever to anything but yourself. You are a comic little figure, hopping from the cradle to the grave. Yes, that is our trouble—we take ourselves too seriously; but Caprona should be a sure cure for that.” She paused and laughed.
“You have evolved a beautiful philosophy,” I said. “It fills such a longing in the human breast. It is full, it is satisfying, it is ennobling. What wondrous strides toward perfection the human race might have made if the first man had evolved it and it had persisted until now as the creed of humanity.”
“I don’t like irony,” she said; “it indicates a small soul.”
“What other sort of soul, then, would you expect from ‘a comic little figure hopping from the cradle to the grave’?” I inquired. “And what difference does it make, anyway, what you like and what you don’t like? You are here for but an instant, and you mustn’t take yourself too seriously.”

Tarzan of the Apes, young and savage beast of the jungle, wondered at the cruel brutality of his own kind. Sheeta, the leopard, alone of all the jungle folk, tortured his prey. The ethics of all the others meted a quick and merciful death to their victims.
Tarzan had learned from his books but scattered fragments of the ways of human beings.