Why did flatbread dominate the Middle East but Europe adopted raised breads?

I'm going to agree with Szczerzo about this being an anthropologic question, but I'm going to disagree about the cause. While nomadic lifestyles was an influence, it's not causative.

I'm also going to ignore the distinction made about raising agents in the OP, because it's factually incorrect; most Arab/Levantine/Turkish/Kurdish breads use yeast. Instead, I'm going to answer the distinction between loaf bread and flatbread.

Specifically: loaf bread is an aberration, not flatbread. You find flatbreads around the world in every society that has access to any kind of grain anywhere. Europe, Asia, Africa, Americas, Malaysia, everywhere. Some are raised (yeasted) and some are not. Some are filled and some are not. All grains are used: wheat, barley, millet, rice, lentils, corn, etc.

Whereas: loaf bread pretty much only shows up in Egypt (and nearby) and in Europe, and there's good reason to believe that the latter two regions learned it from Egypt. Thing is, loaf bread requires several different things to be easily and cheaply available in the same place:

• Wheat or barley (high-gluten flours)
• Ability to build brick, stone, or earthen ovens (this is where nomadism isn't compatible)
• Ability to cultivate starters (both the right grains and the right weather)
• Inexpensive, but hot, fuel for ovens (e.g. wood)

This combination simply didn't happen in too many places; either people lacked suitable grains, lacked cheap fuel, didn't build ovens, or simply never got started (the Babylonians appear to only have made flatbread, for example, despite having all the right ingredients and tools).

So it's really not so much a question of "why did X culture only make flatbread" as "why did these three places make loaf bread?"

If you're interested in this, I highly recommend the book Six Thousand Years Of Bread.

It's actually an anthropologic question.

It's more due to Europe being settled down while Middle Eastern peoples were still nomadic. Raising bread, even with agents, is very hard when you move or don't have much time. For a raised bread you need a starter and few hours; for a flat bread you need a few minutes.

Not to mention flat bread can be baked ON an oven or grill while you cook other food alongside within minutes (it takes me around 10 minutes to prepare 20 flats) while European bread needs its own oven and around 1 hour to make.

It's also worth mentioning that many flatbreads have a rather long storage life. For instance, the Sardinian pane carasau is split and cooked a second time so that it could be used on months long trips.

It's quite possible that the different climates and jobs led to differences in bread making.

Perhaps the difference is not so much between leavened and unleavened as between flat and loaf. In colder climates, there is an existing need for a persistent fire, which has been lit for heating, as well as cooking. In those cultures, ovens and baking are more likely to arise. Even the leavened breads of the Middle East and South Asia tend to be flat, and more quickly cooked.

Given a persistent fire and an oven, loaf breads have the advantage of economy of scale. More weight of them can be produced, without the need for constant attendance, in larger simultaneous batches, than of flat breads.

As @Marcin stated in the comments above, there are no sources for the answers given, and many of the answers have issues:

• Materials, it may not be the prairie, but wheat, spelt, barley, and rye were all available and used for breads even in the ancient Middle East
• Resources, sure, there's less wood for ovens and flatbread cooks more quickly, but desert temperatures are higher, ovens hold heat more efficiently, and the Middle East had plenty of ovens and kilns. Not only that, but plenty of things other than wood burn, having fire in the freezing night temperatures of the desert is essential, and nomadic desert folk still keep campfires going and cook food.
• Lifestyle, yeah, lots of nomads, herders and the like, but like @Marcin stated, cities existed. Not only that, but cities tend to be cultural centers as well. We tend to define a people's cuisine and culture by what large centers of life do, not by their more sparse and scattered population.
• Shelf Life, c'mon, if anything, the dry Middle East is going to have a longer shelf life for goods than all the moisture up north.

But, all that is unsourced speculative rebuttal. If I had to pick a reason, it's yeast. Even in Europe, when you look at the fairly well-documented history of beer and wine (http://www.thecomicbookstoryofbeer.com), people relied on wild yeasts. The microscopic world wasn't a concept and yeast was obtained by luck mixed with trial-and-error. Wild yeasts may be more abundant in the moist, plant-rich environment in Europe; they are spread in the air and in the foliage. While some Middle Eastern beer was made from fermented bread, it is possible that much of the yeast for beer and wine may have come from imports. While beers and wines were made in the Middle East, yeast from one batch is used to make the next (even today, wherever they are made). Unlike in spirits, in breads much of the yeast dies in the baking.

How much more convenient it must be to mix together some flour and water, maybe some oil and salt, throw it on a sheet of metal that's been sitting in the sun or over your campfire, and watch it turn into a pita.

Tandoor style ovens commonly used in the Middle East and Central Asia where you cook the dough sticking it to the walls only work with flatbreads.

The process of leavening Uzbek non, for example, is similar to most Western loafs but it is flattened with a bread stamp right before going into the oven.

I don't think the lack of fuel is the reason since there places with thick woods but still baking flatbreads (The Caucasus or the Southern shore of the Caspian Sea.)

Passover has potentially played a large role in the development of a culture that uses unleavened breads more often, starting (as mentioned in Exodus in the Old Testament of the Bible) when Moses led the children of Israel out of Egyptian bondage.

Passover is a religious observance among the Jews commemorating the departure of their ancestors from Egypt. They were to eat unleavened bread for seven days each time they had the Passover. The observance was also for the other eleven tribes of the House of Israel (not just the tribe of Judah, known as the Jews).

Deuteronomy 16:3 tells us this about the Passover:

"Thou shalt eat no leavened bread with it; seven days shalt thou eat unleavened bread therewith, even the bread of affliction; for thou camest forth out of the land of Egypt in haste: that thou mayest remember the day when thou camest forth out of the land of Egypt all the days of thy life."

Of course, there are a lot more people in the Middle East than the Jews, and unleavened bread may have plenty of other reasons for being popular—but I'm sure Passover contributes to that (including in cultures that don't celebrate Passover, since they may have been influenced by the food habits of their neighbors, much as those in the USA have been with Mexican food).