Abstract
Domestication is an evolutionary process with humans in the role of selection agents. The two critical steps initiating a suite of changes that characterize domesticated cereals dealt with altering the dispersal strategies of wild grasses: grain retention on the mother plant for direct harvest and easy release of the grain by threshing. In addition to human manipulation of evolutionary processes, other natural hybridization events increased diversity and adaptability of domesticated cereals and cereal weed race complexes. Each of the major grains has followed a distinctive path from wild to domesticated forms with one or more progenitor species involved and in some cases, an associated development of weed races. Barley, maize, pearl millet, oats, rice, rye, sorghum, and wheat are the dominant grain staples in acreage, market share, and research attention. Yet, a far larger number of cereal species are the mainstay in subsistence farming communities throughout the developing world. Phylogenetic reconstruction of both domestication and the natural speciation processes shaping cereal grains is still underway. Developing more detailed pictures of the underlying relationships and causative evolutionary mechanisms will provide researchers with precise roadmaps for exploiting genetic diversity. Similarly, application of the knowledge gained from genome sequencing of the major grains and development of the Brachypodium and Setaria grass model systems will open a wider range of avenues for improving agronomic traits.