Mars] The Beast-Jewel Of Mars

The Beast-Jewel of Mars is a science fiction novella by Leigh Brackett.
Bark Winters was a painting, shambling ape, fleeting through dark and echoing pits of horror. Behind him hissed the lashes of the jeering mob, savagely exultant at having debauched still another proud Terran into something that crawled. All the dark secrets of Terran evolution were laid bare in this garden of evil, under that prism of hell!
The wise men of Caer Dhu were not so wise. They found the secret of Shanga, and they escaped their wars and their troubles by fleeing backward along the path of evolution.
The Beast-Jewel of Mars was first published in Planet Stories magazine in 1948. E-book: ePUB, 15,000 words, average reading time 1 hour and 15 min. 
Leigh Douglass Brackett (1915–1978) was an American author, particularly of science fiction, and has been referred to as the Queen of Space Opera. She was also a screenwriter, known for her work on such films as The Big Sleep (1946), Rio Bravo (1959) and The Long Goodbye (1973). She was the first woman shortlisted for the Hugo Award.