is therefore constrained to a more or less narrow zone around the Mediterranean Sea, except in the Maghreb and in the Iberian Peninsula, where it is distributed more widely, and on the islands of the Mediterranean, where it is widespread. The Tunisian historian Mohamed Yassine Essid similarly defines the region by the olive's presence, along with bread, wheat, and the grape as the "basic products of Mediterranean folk cuisine": Other authors question that there is any such common core: Some writers include the cuisines of the eastern Adriatic coast of Dalmatia – Albanian, Montenegrin, and Croatian, while most do not mention them. Some writers also include areas not touching the Mediterranean Sea or supporting olive cultivation, including Serbian, Macedonian, and Portuguese cuisine. Key ingredients Essid identifies the "trinity" of basic ingredients of traditional Mediterranean cuisine as the olive, wheat, and the grape, yielding oil, bread, and wine respectively. The archaeologist Colin Renfrew calls this the "Mediterranean triad". Olive The olive appears to come from the region of Persia and Mesopotamia, at least 6,000 years ago. It spread from there to nearby areas, and has been cultivated since the early Bronze Age (up to 3,150 BC) in southern Turkey, the Levant, and Crete. The ten countries with the largest harvests (in 2011) are all near the Mediterranean (Portugal being the tenth largest): together, they produce 95% of the world's olives. The olive yields bitter fruits, made edible by curing and fermentation, and olive oil. Some 90% of the fruit production (1996) goes into olive oil. The Mediterranean region accounts for the world's highest consumption of olive oil: in 2014, the highest-consuming country, Greece, used 17 kg per head; Italy, 12 kg, Spain, 13 kg; the United States for comparison used only 1 kg per head. Wheat Wheat was domesticated in the Fertile Crescent, in and near the Levant some 10,000 years ago. Its ancestors include wild emmer wheat; this was hybridised, harvested and sown to create domestic strains with larger grains, in ears that shatter less readily than wild forms. It was spread across the Mediterranean region as far as Spain by 5,000 BC. Wheat is a staple food in the Mediterranean region. Wheat bread was already critically important in the empire of Ancient Rome, which included the entire region; at that time, around 2,000 years ago, North Africa was the "breadbasket" of the empire. Other staple wheat-based Mediterranean foods include