First precondition, is lots of population density in a particular area, which ideally means very fertile land surrounded by a sharp dropoff in density beyond that, hence river valleys.
Second precondition, is that you need a reason for people to cooperate (or be forced to cooperate) in large groups, and there needs to be enough coercion to maintain this.
One idea about why this might happen is that once the population density gets high, and humans tending some degree of warfare, then people will tend to band together in larger groups to form larger "war bands". These also tend to have lower size relative to the group (as more people pool together the "army" that they need include relatively fewer of the adult males).
This is then what results in cities, as centres of coordination for larger military groups, and as the result of war bands who form relatively rich elites with enough residual wealth for trade, etc. (as they're drawing a marginal part of the income of a large population).
The other idea about why this may happen is for irrigation, and for control of river flooding and such, agricultural works that benefit a large amount of people, but need large groups to coordinate them.
So ideal for civilization is probably high population density, lots of local competition, and also irrigation or river fed agriculture that requires a lot of coordination.
(Hence one idea about why Europe was not a place to which civilization emerged early, despite being a place where early farmers actually moved to quite early. Much of the continent probably did not maintain very high population densities from the slightly ill adapted Near Eastern agricultural toolkit suited to a warmer climate, and agriculture tended to be rain fed. Then it tended to adopt pastoralist elements that pushed further towards lower population densities and to increased mobility which again pushed further against large scale cooperative agricultural works.)
Second precondition, is that you need a reason for people to cooperate (or be forced to cooperate) in large groups, and there needs to be enough coercion to maintain this.
One idea about why this might happen is that once the population density gets high, and humans tending some degree of warfare, then people will tend to band together in larger groups to form larger "war bands". These also tend to have lower size relative to the group (as more people pool together the "army" that they need include relatively fewer of the adult males).
This is then what results in cities, as centres of coordination for larger military groups, and as the result of war bands who form relatively rich elites with enough residual wealth for trade, etc. (as they're drawing a marginal part of the income of a large population).
The other idea about why this may happen is for irrigation, and for control of river flooding and such, agricultural works that benefit a large amount of people, but need large groups to coordinate them.
So ideal for civilization is probably high population density, lots of local competition, and also irrigation or river fed agriculture that requires a lot of coordination.
(Hence one idea about why Europe was not a place to which civilization emerged early, despite being a place where early farmers actually moved to quite early. Much of the continent probably did not maintain very high population densities from the slightly ill adapted Near Eastern agricultural toolkit suited to a warmer climate, and agriculture tended to be rain fed. Then it tended to adopt pastoralist elements that pushed further towards lower population densities and to increased mobility which again pushed further against large scale cooperative agricultural works.)