Solution: There are mainly eight types of food grains consumed by modern human society, namely, wheat, maize, millet, sorghum, mustard, oat and rice. These plants were present in the form of weed in different areas, which were later grown as seed by a human being at different places, in different times. Although, barley was the first grain to be cultivated by human beings during 8000 B.C. in western Asian countries located between the northeast Mediterranean Sea and Iran. Later, in the same area, wheat was also cultivated around 8000 B.C.