The advantages of herding are obvious. First, you get to be a cowboy. Also, animals provide meat and milk, but they also help out with shelter because they can provide wool and leather. The downside is that you have to move around a lot because your herd always needs new grass, which makes it hard to build cities, unless you are the Mongols. By the way, over the next 40 weeks you will frequently hear generalizations followed by unless you are the Mongols. But anyway, one of the main reasons herding only caught on in certain parts of the world is that there aren't that many animals that lend themselves to domestication. Like, you have sheep, goats, cattle, pigs, horses, camels, donkeys, reindeer, water buffalo, yaks, all of which have something in common.