Next week’s episode of The Insight is going to be on Denisovans. It’s a long one because so much has come out in the last few months on the specific topic, as well as the broader framing issues (e.g., the discovery of a new human species on Luzon).
One of the major points Spencer and I discussed is how important it is to understand general trends in the hominin lineage, that is, humans, before the great expansion ~60,000 years ago. For example, Neanderthals and Denisovans were very different in their paleoecology and biogeography. Neanderthals seem relatively homogeneous (probably due to repeated mass die-offs). In contrast, the “Denisovans” look to have been very deeply diverged within their clade. If the latest work is correct, and some Denisovan lineages split more than 400,000 years ago and persisted down to >100,000 years ago, then the differences between Denisovans may have been considerably greater than between any modern human lineages. For example, the Khoisan diverged from all other humans ~200,000 years ago, and there are possible deeper lineages, but not that much deeper.
Right now what you know about the Denisovans are from genomes in the Altai region. Imagine if we extrapolated to all modern humans from Altaians? It seems entirely likely that the Denisovan lineage was very diverse because it occupied very diverse territory geographically.
But diversity aside, one of the things I like to point out to people, is that there was an overall trend of encephalization among hominins. Neanderthal brains were growing larger too. We need to understand the natural history of all human lineages to understand what happened 60,000 years ago. I am coming to the conclusion that it wasn’t some incredible miracle of a behavioral big bang, but the inevitable outcome of systemic forces in hairless ape evolution that started ~2 million years ago.