They were an established population with adapted lifeways that had been in development for long enough to produce the material sophistication visible in the archaeological record.

The 2004 paper could not answer the most fundamental question about who these people were.

That would require biology, not just archaeology.

It would require DNA.

And extracting readable DNA from 31,000-year-old teeth recovered from the Siberian permafrost was, until very recently, not possible.

The science that would eventually reveal the Ancient North Siberians had not yet been developed.

How You Read A Genome From A 31,000-Year-Old Tooth