Re civilization -- it's not just about living in cities; that's a side effect of homes becoming permanent. It's about changing a people's way of life from nomadic to agricultural. The source of their subsistence is changing from hunting/gathering -- and moving on when the area they're in is hunted/gathered out -- to making the same piece of land feed them permanently by sowing/pasturage.
If Alexander had known what we know today, he'd have been able to say this when he settled nomads into cities: "Here's the deal. You'll all be shorter, but there will be lots more of you." Seriously, this is true, though I don't recall where I read it. When people change from a nomadic way of life to an agricultural, the food supply becomes more plentiful, ergo more people, but the ratio of protein to carbs in everyone's diet goes down and therefore they don't grow as tall.
Staying in one place has some distinct advantages. You can build things that are permanent, and, since you're going to stay in them rather than folding them up and carrying them away, it's feasible to make them large, solid and truly impressive, the ultimate example being the things the Egyptians built. Agriculture means more surplus value (that which people produce over and above what they consume); and that means more time available for those who have the talent to develop things like science, art and philosophy. It also means greater concentrations of wealth and power; you can't have a standing army like Philip's, for instance, if everyone's full-time labour is required to bring in enough food to feed everyone. It also gives an agricultural culture a military advantage over nomadic ones; the settled life, in general, is safer. All these things were part of the impetus pushing a general change for all humanity from hunting/gathering to agriculture.
So when Alexander was growing up, he lived in a palace that could not have been built but for the corn sown on the great plains of Makedonia, watching plays, reading writings and learning philosophy that could not have existed but for the corn grown elsewhere in the Greek world. Indirectly, agriculture made him. To have a bias towards agriculture over nomadism, to see nomads as backwards and in need of taming and training in the "proper" way of life, would have been natural. Alexander's idea that he was doing them a favour doesn't preclude the standard exploitation of lower classes by upper (including the king); it just means that he thought that even as peasant farmers under the protection of a king and his armies, they were better off than they had been.
In fact according to Arrian he made this argument to his army using themselves as his example -- since the civilization of upper Makedonia was recent enough to be within living memory. Trans. Yardley:
Philip found you a tribe of impoverished vagabonds, most of you dressed in skins, feeding a few sheep on the hills and fighting, feebly enough, to keep them from your neighbours - Thracians and Triballians and Illyrians. He gave you cloaks to wear instead of skins; he brought you down from the hills into the plains; he taught you to fight on equal terms with the enemy on your borders, till you knew that your safety lay not, as once, in your mountain strongholds, but in your own valour. He made you city-dwellers; he brought you law; he civilized you. He rescued you from subjection and slavery, and made you masters of the wild tribes who harried and plundered you; he annexed the greater part of Thrace, and by seizing the best places on the coast opened your country to trade, and enabled you to work your mines without fear of attack. Thessaly, so long your bugbear and your dread, he subjected to your rule, and by humbling the Phocians he made the narrow and difficult path into Greece a broad and easy road.
"He brought you down from the hills into the plains" means, of course, from non-fertile land to fertile. They had been apparently living not an entirely nomadic life -- viz the mountain strongholds -- but one that was a sort of mix, with herding, some permanent settlements and a shift away from hunting towards raiding, which isn't that different, as a source of meat. What Philip would have done was imposed an end to raiding, the endless cycles of sacred revenge that would have made every tribe the mortal enemy of the tribe in the next valley, and the resulting death toll. Some would argue that wasn't a bad deal.
Now nomads tend to have their own opinions about that, which is why Philip and Alexander both had to force it on them, of course. (It's incorrect, incidentally, both on the part of Alexander and whoever wrote it upthread, to say nomadic cultures are lawless. They aren't amenable to living according to laws imposed on them from outside, but like all cultures, they have their own, no less strict, or wise, for not being written down.)
More anon.
Warmly,
Karen