Concept I came up with talking to
@The Dutch Ghost about his Texas setting.
Space Apes
Houston, the Drowned City, haunt of salvagers, fishermen, and masked merchants from the haunted lands of N'awlins. Peaking out of the endless mire are steel and stone skeletons, gothic and art deco corpses of the Old World. The denizens of the Drowned City make their homes and camps in these towering islands, but be warned - if you see a campfire burning bright in the night in one of these ruins, its tender may not be human.
Not far away from Houston was the United States Space Administration's headquarters, center of American starfaring for over a century. On its grounds was a large colony of chimpanzees, raised from the earliest days of space travel for testing. The colony has been maintained, both for space-related testing and more general experimentation. Following the war, a troop of chimps escaped. In a world nearly devoid of humans, they were able to survive by scavenging. They migrated to the ruins of Houston and have been there ever since.
The chimps are clearly not the same as wild, pre-War chimps. For one thing, they tend to stand on their hind legs a lot more often. For another, they use tools with some proficiency albeit rudimentary ones - spears, clubs, hammers. Tools in need of fine motor skill are largely beyond them, but salty scavengers will swear up and down that they've seen some of the wiser ones toting shot-guns. They do build fires, though not in any complex way - they usually just gather a pile of dried vines and garbage, and then repeatedly smash a power cell or microfusion cell until it explodes.
They seem capable of planning, setting up ambushes for unweary humans. They do not seem to have speech, mostly screeching at each other and humans, but a keen observer may note subtle movements of their hands. They have queer cultural customs, setting up shrines to apparently random objects - cigarette machines, Mr. Jangles dolls, Cat's Paw magazines. The apes leave 'valuable' objects (broken glass, distinctive rocks, energy cells) at these shrines in adoration, and will viciously defend them from any human interloper. Elderly chimps will come to these shrines and wait for death, leading to an accumulation of skeletons and mummies. The oldest and most elaborated of these shrines often center around objects bearing the distinctive seal of the USSA (much to the chagrin of the Signal-Listeners).
How exactly these chimps have taken a step up on the evolutionary scale is unclear. It would seem obvious that radiation played some role. Many speculate that there were pre-War experiments to boost their intelligence so they could be used for labor. Perhaps these are unholy human-ape hybrids, a warrior species of humanzees to destroy the ChiComs. More boring commentators postulate that their modest intelligence simply came as a result of selective pressures of living in a testing facility, and the accumulation of community memory thanks to the gift of sign language, allowing chimpanzees to build an actual culture.
These are speculations for the ivory tower set, however. Those humans who dwell in the Drowned City know Space Chimps only as an implacable enemy, savages with no desire to ever be at peace, and maneaters to boot. Indeed, the chimps have no compunction about eating men, though men are more than happy to return the favor - the chimps are not human, afterall. The chimps are valued as curios, jesters and colosseum fighters. The masked voodoo traders put the greatest value on chimps, paying top dollar for a live one to be exported back to the menageries of Louisiana warlords; though they're more than happy to by their hides, paws, or meat instead.
Conflict is never-ending between the humans and apes. As more salvagers and fishermen come to the Drowned City, the number of chimps has dwindled. Their eventual extinction looks to be a certainty, unless some benevolent wastelander manages to decipher their crude hand-gestures.
