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People are justifiably excited about the discovery that a 160,000-year-old mandibular fragment, excavated in 1980, can now be recognized as related to the Denisovans. But few are pointing out how this shakes up assumptions. nature.com/articles/s4158… 
It's very cool to identify a hominin at 3200 meters (10000+ feet) altitude, estimated at 160,000 years ago. The earliest reported evidence prior to this from the Tibetan Plateau was under 40,000 years ago. Makes sense of EPAS1 adaptation from Denisovans. But..
..did archaeologists just miss 120,000+ years of occupation of the entire region up to now? How much farther back have they missed? We are going to see the 160,000-year date again and again, but this is a minimum from U-series of the encrusted carbonate on the bone. It's older.
When people say we know when humans first reached any region, that is usually based on an assumption that sampling intensity is adequate. Each new discovery like this tells us that the sampling intensity has actually been much poorer than assumed.
I find the dental morphology fascinating. Two big third molars from Denisova Cave have suggested that Denisovans had large dentitions. The Xiahe mandible lacks a third molar entirely -- M3 agenesis. But the M1 and M2 are both pretty large.
Were Denisovans a distinctively big-toothed population? The big-toothed Denisovan model doesn't fit super well with the idea that many Chinese specimens belong to that population (Chinese erectus had comparatively small teeth, later Chinese fossils even moreso) Maybe they don't.
Many most interesting, we now begin a test of wills between geneticists and paleoanthropologists. People have long wondered, were Denisovans a species? Or just a population of humans? Or a population of Neanderthals? Or several species, even?
Geneticists working with the ancient genomes have been admirably restrained. Denisovans. A population name similar to Neanderthals. Agnostic on taxonomy. They've even held back from talking about "hybridization". I think that has been the right decision and remains so.
But Xiahe provides a mandible with morphology, and protein sequence data. Some paleoanthropologists are going to be sorely tempted to diagnose a species.
I think naming a new species for any fossil in this group at this time would be the wrong decision. As we are learning more and more about the population structure and complexity, we are so close to knowing a fuller picture. Taxonomy can wait, honestly, until we know more.
The Xiahe specimen predates the Denisova discoveries in both geological age and discovery time. Neither matters formally to taxonomy, which is just a race to publication. But do we really have a reason to keep "Denisovans" as the name as more fossil discoveries are made...
