After the middle of the fourth millennium the increase of permanently settled population in central Babylonia was minor and can be explained as the result of natural growth. In the south around the city of Uruk, however, there was an enormous escalation in the area occupied by permanent settlement.
(from A History of the Ancient Near East by Marc Van De Mieroop)
While I have no difficulties in understanding of this excerpt general meaning, I wonder why the bolded (by me) phrase is not prepended with an article here.
According to dictionaries (for example, Merriam-Webster), the word settlement may refer to either a place or the process of settling (of course, we do not consider other, irrelevant, meanings).
As far as I can see, the author relates about the specific inhabited place - that around the city of Uruk. And it is hard to say that permanent settlement conveys the meaning of the generalized idea of all settled places here, so the phrase needs the definite article, doesn't it?