context: In Eurasia, the Sumerians started to live in villages from about 8,000 BC, relying on the Tigris and Euphrates rivers and a canal system for irrigation. Ploughs appear in pictographs around 3,000 BC; seed-ploughs around 2,300 BC. Farmers grew wheat, barley, vegetables such as lentils and onions, and fruits including dates, grapes, and figs. Ancient Egyptian agriculture relied on the  Nile River and its seasonal flooding. Farming started in the predynastic period at the end of the Paleolithic, after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as flax and papyrus. Agriculture in India, wheat, barley, and jujube were domesticated by 9,000 BC, soon followed by sheep and goats. Cattle, sheep and goats were domesticated in Mehrgarh by 8,000–6,000 BC. Cotton was cultivated by the 5th-4th millennium BC. There is archeological evidence of an animal-drawn plough from 2,500 BC in the Indus Valley Civilization. Agriculture in China, from the 5th century BC there was a nationwide granary system and widespread sericulture. Water-powered grain mills were in use by  the 1st century BC, followed by irrigation. By the late 2nd century, heavy ploughs had been developed with iron ploughshares and mouldboards. These slowly spread westwards across Eurasia. Asian rice was domesticated 8,200–13,500 years ago in China, with a single genetic origin from the wild rice Oryza rufipogon. Agriculture in ancient Greece and Roman agriculture, the major cereals were wheat, emmer, and barley, alongside vegetables including peas, beans, and olives. Sheep and goats were kept mainly for dairy products.
question: Which was cultivated first, cotton or wheat?
answer: wheat