"Historic documents confirm that wheat is the earliest field crop used for human food processing ... It also became the leading grain used for human consumption due to its nutritive profile and relatively easy harvesting, storing, transportation, and processing, as compared to other grains. The earliest varieties, grown 12,000–17,000 years ago in the Near East, were and . Continued breeding resulted in the development of new varieties around the world that often became adapted to areas previously unsuited for the cultivation of wheat. The main wheat varieties grown today are , which is a hexaploid with six groups of seven s in each group. This species includes hard red winter, hard red spring, soft red winter, and white wheats. Another wheat durum is a tetraploid, containing four groups of seven chromosomes totaling 28 chromosomes. The botanical name of is Triticum durum. A limited area is planted with the soft white wheat variety of Triticum aestivum, subspecies compactum, commonly known as . Currently about 4000 different wheat varieties are grown around the world."