Maize,also known as corn, is a cereal grain that was domesticated in Mesoamerica. The domestication of maize is of particular interest to researchers - especially archaeologists, geneticists, ethnobotanists and geographers. Recent genetic evidence suggests that maize domestication occurred 9000 years ago in central Mexico. Perhaps as early as 1500 BC, maize began to spread widely and rapidly. It is unknown what precipitated its domestication, because the edible portion of the wild variety is too small and hard to be eaten directly, as each kernel is enclosed in a very hard bi-valve shell. However, it has been demonstrated that the kernels of teosinte can be readily "popped" for human consumption, like modern popcorn. Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain.