The book is Wengrow and Graeber. Your references post date their work - Graeber has been dead for years. Much of the material under discussion is in this 2015 essay.[^1] In fact of course settled hunter gatherers, so to call them, have been known for decades, e.g. Jomon Japan; this isn't the issue anywhere.

Some of the spectacular phenomena and constructions they attempt to explain depend on non-settlement for much of the year. But in temperate regions even in the eurasian ice age we find seasonal congregation of huge populations in conditions of temporary abundance e.g. salmon runs, seasonal migration of game through narrow alpine chasms, etc. A leading motif is that in these congregations surprising phenomena can emerge e.g. insane stone works, temporary political structure, etc. Thus also the discussion of ice-age burials like that in Sunghir Russia 30,000 years ago a couple boys buried with "10,000 hand-carved mammoth ivory beads, fox teeth pendants, and finely crafted mammoth ivory spears"

[^1]: https://eprints.lse.ac.uk/62756/1/__lse.ac.uk_storage_LIBRAR...