You might be better served trying /r/Anthropology, this sub is more for non-speculative type discussions about recorded historical facts.

Islands are excellent refuges for species that are being wiped out on mainlands, and one of our most recently extinct relatives is the diminutive homo floresiensis, they survived until less than 20,000 years ago when humans reached their island. Their extinction is so recent that the human locals of the island of Flores still tell stories of short, wide nosed people who try to steal their children. I think that the only chance for them and other isolated late survivors to have lived alongside us is if they were discovered in the modern era. Even up to a couple of hundred years ago they would probably have ended up as trophies and in zoos, and we're not doing too much better with our nearest extant relatives today.