This is quite an interesting story about yogurt’s various uses by nomadic pastoralists:

It is more generally accepted by food historians that sometime around 5000 BC, nomadic pastoralists living in Central Asia discovered goat’s-milk yogurt and the technique of making it on purpose from a starter culture. This was an extremely important nutritional event, because in hot climates, long before the development of modern refrigeration or the invention of pasteurization, milk went bad within hours or days. Freshly made cultured yogurt contains up to a billion live cells per milliliter of L. bulgaricus and S. thermophilus, and this huge concentration discourages the growth of other, possibly disease-causing, bacteria at the same time that fermentation helps preserve the milk and improves its digestibility by breaking down the lactose. For millennia, making yogurt was the only known method of safely preserving milk without drying it.

The Yörük, an Oğuz Turkic people, are the earliest Turkic inhabitants of Anatolia, thought to have originated when Turkmen tribes migrated into Anatolia from the north and mixed with indigenous Anatolian peoples. Their name comes from the Turkish verb yürümek, “to walk,” and they still migrate within well-defined areas, respecting the grazing and water rights of other Yörük families and settled villagers alike.

http://www.saudiaramcoworld.com/issue/200804/of.yogurt.and.yoruks.htm

For a good book about the Yörük people of Turkey, read "The Caravan Moves On" by Irfan Orga!