Sometimes it can be a struggle to make science fiction more interesting than science fact. In The Start of Eternity, a fan fiction sequel to Isaac Asimov's time travel novel, I imagined that 20,000 years ago there were four distinct subtypes of humans on Earth. Further, I Imagined that when the Neanderthals became extinct, the last ones alive on Earth lived in central Asia (see map).
Today I heard about the discovery of Denisova hominin, what might have been an actual fourth human subtype that shared Earth with Neanderthals, Homo floresiensis and modern humans. So far, all that is known about this subtype of human comes from study of a finger bone. The bone yielded mitchondrial DNA which suggests "Denisova hominin" branched off from the Neanderthal/modern human lineage about a million years ago.
In The Start of Eternity, there are characters such as Overseer Doltun who could possibly be descended from "Denisova hominin". Before the discovery of "Denisova hominin" I was imagining that the Overseers were possibly Homo ergaster or a similar ancient human variant.
Ancient Denisovan-related mitochondrial DNA from Spain (2013)
Evolutionary History and Adaptation from High-Coverage Whole-Genome Sequences of Diverse African Hunter-Gatherers