The beginnings of human civili zation can be traced back to the time , ne- ly 12 ,000 years ago , when th e early humans gradually ch anged from a life of hunting and gathering food , to producing food. This beginning of pri- tive agriculture ensured a dependable supply of food , and fostered the living together of people in groups and the development of s o c i e ty. During th is time, plant s e e ds were recognized a s a valuable s o ur c e of food and nutrition , and began to be used for growing plants for food. Ever s i n c e , plant seeds have played an important role in the development of the human civilization . Even today, s e e ds of a few crop s p e c i e s , s uc h as the cereals and legume s, are the primary s o u r c e of most human food , and the predominant commodity in international agriculture. Owing to their great importance as food for human s and in international trade , seeds have been a favorite object of s t u d y by developmental biologists and physiologi sts , nutritionist s and chem i sts . A wealth of useful information i s available on th e biology of seed s .