That's the traditional answer, but it's wrong. Göbekli Tepe[1] decisively pre-dates agriculture. Although it wasn't inhabited, it displays a level of technology and social organisation on par with city-building. But agriculture definitely had nothing to do with it.
Not saying that I've got a good answer for what did happen -- just that agriculture wasn't it.
If it wasn't permanently inhabited, then it's not a city. There are the remains of massive camps in Russia built out of Mammoth bones and tusks that held many thousands of people, made possible by massive culls of migrating herds, but these are not permanent settlements either.
Living permanently in the same place on a large scale is a completely different way of life compared to living a mainly nomadic life and gathering at special sites from time to time, even if you make a permanent mark on those sites.
Permanent populations are not a sign of civilization. Many religious sites today are sparsely populated except for once/twice a year, but we still have civilization. The Mongols were civilized even when they were raiding the entire old-world and establishing many dynasties. They had writing, religion, generals and well-organized armies, a bureaucracy, laws and customs, tariffs, etc, just not a single plot of land they went to sleep on every single night. Heck, even NYC doubles in population daily [0], those people may be daily commuter nomads, but they are 'civilized' people.
One area in the world where society may have evolved differently doesnt seem to be enough evidence to debunk the idea that the agricultural revolution gave rise to cities. Isn't this just an outlier... if it even does predate agriculture.
It's an outlier. That's not deniable. It doesn't disprove the fact that agriculture lead to cities in so many other places... technically agriculture may not have been a prerequisite to cities, because of this one exception... cool. To say that this exception disproves the idea entirely, is to assume that all places evolved identically, which is just dumb.
Agriculture allows higher population density - a nice alternative to starvation, war, infanticide. But agriculture is less pleasant than hunter-gathering, so you avoid it til you have serious population problems.
Alternatively, fishing also allows for high population density's. But, those city's are now under a lot of water.
Further, civilizations based on wood instead of stone may have vastly fewer remnants. Which creates bias as we assume civilizations started in areas without much wood.
Or, it's actually not food that's the limitation but rather something else like culture with farming going back much further.
So what? No one is claiming that prehistoric people couldn't build anything. But without agriculture you can't have dense cities or anything like civilization. The population that can be supported by hunting and gathering alone is tiny.
*Citation needed. Every source I've seen says that it is.
> But without agriculture you can't have dense cities or anything like civilization. The population that can be supported by hunting and gathering alone is tiny.
Göbekli Tepe says otherwise. It was a truly large-scale undertaking, requiring the highly-organised planning, engineering, and construction efforts of many hundreds, possibly thousands of people. And all the evidence points to these people being hunter-gatherers, not agrarians.
If true, it might not be agriculture that lead to all cities, but the abundance of food that did (which is more common in agriculture-backed societies). Maybe this was just a particularly good spot for hunting and gathering over a long period of time.
Seems to me that it could still be correct. It seems likely that humans were smart and well-equipped enough to build sites like Göbekli Tepe before the agricultural revolution, but the vast majority of them simply didn't have enough time to do so.
Your citation does not support the "decisively predates agriculture" claim, and in fact refers to early agriculture at the site as one of the competing interpretations.
Göbekli Tepe was built ~11,500 years ago, and it probably isn't a coincidence that early agriculture was developed in the same area -- about 1,000 years later. The early agriculture reference that you mention concerns the fact that the was abandoned as early agriculture started to take hold:
> Around the beginning of the 8th millennium BCE Göbekli Tepe ("Potbelly Hill") lost its importance. The advent of agriculture and animal husbandry brought new realities to human life in the area, and the "Stone-age zoo" (Schmidt's phrase applied particularly to Layer III, Enclosure D) apparently lost whatever significance it had had for the region's older, foraging communities.
I haven't seen any sources citing evidence for Göbekli Tepe post-dating agriculture, but there are many lines of evidence that it pre-dates it -- such as an absence of cultivated grains, granary structures, or other evidence that one sees as agriculture actually gets going. All the plant remains that have been found are wild varieties. Thus the mainstream assumption is that Göbekli Tepe was built by hunter-gatherers.
Perhaps I am going too far with my speculation, but GT strikes me on two aspects as being highly unusual, with regard to what I "know"[1] about hunter-gatherer societies.
1. The site seems to be built with a plan. Maybe they did not use paper and pencil, maybe they were using some kind of sand table[2]. And there was a number of people involved, who were quite good at stone cutting, and on a large scale. Just have a look at central obelisk and pedestal [3] - those sharp edges, those smooth surfaces. Now, getting good at something requires daily practice, for a long period of time during which one would rather not go around for hunting. So not only there was a population of proto-carpenters but also societal structure to support them, at least for times of learning and construction work.
2. Even more unusual, the site seems to have been abandoned (evacuated?) in planned manner. Great effort has been made to cover it up with huge mass of soil mixed up with broken stones, as if to make it tougher against elements. This, for me, really stands out. AFAIK the norm is, when supporting culture "loses interest" in site maintainance (like, when all its members are dead), the site is being taken over and/or decaying and/or reused by next wave of humans. But not this time.
Quite fascinating.
[1] what I know is subject to change as time goes by and I get updates
Not saying that I've got a good answer for what did happen -- just that agriculture wasn't it.
1: https://en.wikipedia.org/wiki/G%C3%B6bekli_Tepe