Humans have directly influenced the genetic makeup of plants to increase their value as a crop through domestication. The first evidence of plant domestication comes from emmer and einkorn wheat found in pre-Pottery Neolithic A villages in Southwest Asia dated about 10,500 to 10,100 BC. The Fertile Crescent of Western Asia, Egypt, and India were sites of the earliest planned sowing and harvesting of plants that had previously been gathered in the wild. Independent development of agriculture occurred in northern and southern China, Africa's Sahel, New Guinea and several regions of the Americas. The eight Neolithic founder crops (emmer wheat, einkorn wheat, barley, peas, lentils, bitter vetch, chick peas and flax) had all appeared by about 7,000 BC. Traditional crop breeders have long introduced foreign germplasm into crops by creating novel crosses. A hybrid cereal grain was created in 1875, by crossing wheat and rye. Since then traits including dwarfing genes and rust resistance have been introduced in that manner. Plant tissue culture and deliberate mutations have enabled humans to alter the makeup of plant genomes.