I have a theory about how the Camo beast came into existence. My theory is when humans went extinct from the future predators, chimpanzees in africa evolved in african cities, and gained intelligence, and became the african apex predator. I can go into full depth, but since they have the features of an ape, an evolved chimpanzee seems most likely
I agree with the primate part, but chameleon does not seem likely. Chameleons are reptiles, meaing reptiles function better when the sun is out, but are slow and sluggish when darkfalls. However we see the Camo beast extremly quick at night. It's probobly just a new type of mamal. It can't be human made, like a hybrid, because compare it to the Future predator. The predator can regnerate extremely fast, however the camo beast died in a few shots from a gun. We can assume that people hyper evolved bats into predators, but camo beasts are naturally created.
The Predators most likely evolved naturally before they were coled in Series 3.
The Camo-beast could have evoled naturally as well but I believe that humans had some involvement in its creation, like splicing an primates genes with chameleon or cuttlefish DNA for the colour changing.
I might be wrong, but chameleons and cuttlefish aren't the only source of camouflaging. The Arctic hare is brown or grey colored during summer, but as the winter arrives, it moults it's fur and grows new one, this time in a white color. Other Arctic animals, such as the ermine, also posses this ability. They look nothing like the Camo Beast, nor their camouflage is nearly as advanced, but some millon years of evolution could do the work (after all, we were nothing but lil' squirrel-like animals 65 years ago)
However, the hybrid theory is a lot more likely. But instead of a chimpanzee with chameleon/cuttlefish DNA, I bet the base creature could be an aye-aye (which looks a lot more like the Beast) with the spliced DNA of chameleon/cuttlefish, and maybe some human/chimpanzee DNA to give it its intelligence and humanoid shape. The reason of it's low endurance might be that they weren't intended to be "war creatures" like the Predators, or maybe to prevent any incident since it was rated as more dangerous than the Predator (after all, the last one can also camouflage in the enviroment, but isn't practically invisible!)