I read this book in the late 1960s or early 1970s. It may have been an Ace Double.
Plot opens on world 1, there is a base or encampment that is under attack by various forms of non-sentient life, idea is that life on this place is constantly evolving to destroy the human base. An expedition quickly leaves for another planet. On that world there is a coldish desert area where the protagonist lands, it is a tribal, nomadic civilization with lots of wars. He wants to blend in so can't take any technology with him, but does take a very good knife, much better than could be made by native peoples. The planet is separated into this cold zone and another one by a very large cliff or escarpment and there is no contact between the two zones at all.
He spends time with one tribe, the chief uses the knife to execute someone and keeps it. Protagonist is annoyed.
At some point he is thrown into what seems to be a bottomless pit but lands unharmed, more or less, and finds himself able to reach the lower, warmer civilization.
Can't remember any of the rest of the plot, the hero's name may be Jason but.....
Any thoughts?
Plot opens on world 1, there is a base or encampment that is under attack by various forms of non-sentient life, idea is that life on this place is constantly evolving to destroy the human base. An expedition quickly leaves for another planet. On that world there is a coldish desert area where the protagonist lands, it is a tribal, nomadic civilization with lots of wars. He wants to blend in so can't take any technology with him, but does take a very good knife, much better than could be made by native peoples. The planet is separated into this cold zone and another one by a very large cliff or escarpment and there is no contact between the two zones at all.
He spends time with one tribe, the chief uses the knife to execute someone and keeps it. Protagonist is annoyed.
At some point he is thrown into what seems to be a bottomless pit but lands unharmed, more or less, and finds himself able to reach the lower, warmer civilization.
Can't remember any of the rest of the plot, the hero's name may be Jason but.....
Any thoughts?
