<Li> Leonid Grinin argues that whatever plants were cultivated, the independent invention of agriculture always took place in special natural environments (e.g., South - East Asia). It is supposed that the cultivation of cereals started somewhere in the Near East: in the hills of Palestine or Egypt . So Grinin dates the beginning of the agricultural revolution within the interval 12,000 to 9,000 BP, though in some cases the first cultivated plants or domesticated animals' bones are even of a more ancient age of 14--15 thousand years ago . </Li> <Li> Andrew Moore suggested that the Neolithic Revolution originated over long periods of development in the Levant, possibly beginning during the Epipaleolithic . In "A Reassessment of the Neolithic Revolution", Frank Hole further expanded the relationship between plant and animal domestication . He suggested the events could have occurred independently over different periods of time, in as yet unexplored locations . He noted that no transition site had been found documenting the shift from what he termed immediate and delayed return social systems . He noted that the full range of domesticated animals (goats, sheep, cattle and pigs) were not found until the sixth millennium at Tell Ramad . Hole concluded that "close attention should be paid in future investigations to the western margins of the Euphrates basin, perhaps as far south as the Arabian Peninsula, especially where wadis carrying Pleistocene rainfall runoff flowed ." </Li> <P> Once agriculture started gaining momentum, around 9000 BC, human activity resulted in the selective breeding of cereal grasses (beginning with emmer, einkorn and barley), and not simply of those that would favour greater caloric returns through larger seeds . Plants with traits such as small seeds or bitter taste would have been seen as undesirable . Plants that rapidly shed their seeds on maturity tended not to be gathered at harvest, therefore not stored and not seeded the following season; years of harvesting selected for strains that retained their edible seeds longer . </P> <P> Several plant species, the "pioneer crops" or Neolithic founder crops, were identified by Daniel Zohary, who highlighted the importance of the three cereals, and suggested that domestication of flax, peas, chickpeas, bitter vetch and lentils came a little later . Based on analysis of the genes of domesticated plants, he preferred theories of a single, or at most a very small number of domestication events for each taxon that spread in an arc from the Levantine corridor around the Fertile Crescent and later into Europe . Gordon Hillman and Stuart Davies carried out experiments with wild wheat varieties to show that the process of domestication would have occurred over a relatively short period of between 20 and 200 years . Some of these pioneering attempts failed at first and crops were abandoned, sometimes to be taken up again and successfully domesticated thousands of years later: rye, tried and abandoned in Neolithic Anatolia, made its way to Europe as weed seeds and was successfully domesticated in Europe, thousands of years after the earliest agriculture . Wild lentils presented a different problem: most of the wild seeds do not germinate in the first year; the first evidence of lentil domestication, breaking dormancy in their first year, was found in the early Neolithic at Jerf el Ahmar (in modern Syria), and quickly spread south to the Netiv HaGdud site in the Jordan Valley . This process of domestication allowed the founder crops to adapt and eventually become larger, more easily harvested, more dependable in storage and more useful to the human population . </P>

Where is the knowledge of crop cultivation in the americas believed to have originated