A viable, genetically sustainable population might consist of a thousand primates, consisting of small family groups, nomadic by nature, over thousands of square miles. They wouldn’t need fire to keep warm any more than other Northern mammals need fire. And your contention, @keobooks, that sticks and rocks used as tools are recognizable as such may be true, but recognizable as such by whom? By you? Are you a primatologist trained to see the difference between a rock used to deliberately break something and a rock that’s just a rock?
The fact that something has not been been confirmed as scientific evidence doesn’t mean it doesn’t exist, it simply means that the appropriately trained individuals have not seen and /or confirmed it as scientific evidence.
If such primates exist, they wouldn’t necessarily have a sophisticated intelligence or social structure, they may just be good at hiding in remote areas.
And if I were a scientist, I would be reluctant to reveal findings, just based on this thread, where the not-unreasonable idea of a primate species with which we are not familiar is grouped in with UFOs, trolls, elves, Nessie, and other creatures proven to have an origin in myth or hoax.
Again, not saying they exist, but considering the possibility, given geography and other factors, doesn’t seem to be unreasonable.