The present paper reviews the state of cultivated barley,Hordeum vulgare, in Old World agriculture and its domestication through its progenitor, wild barley,Hordeum spontaneum. It focuses on the adaptation, incipient sympatric speciation, and domestication ofH. spontaneumin the “Evolution Canyon” model. The “Evolution Canyon,” at lower Nahal Oren, Mount Carmel, Israel, revealsevolution in actionat a microsite caused by interslope microclimatic divergence across life from viruses and bacteria through fungi, plants, and animals including mammals. The interslope adaptive complexes ofH. spontaneumat “Evolution Canyon” include genetic diversity, drought resistance bydehydrin I, rhizosphere bacteria, andEibi Igene promoter.Isadefense locus and vitamin E components also diverge between the opposite tropical and temperate abutting slopes. A highly likely pre-agricultural collection site ofH. spontaneumis described on the Natufian cemetery of the Oren and Um Usba caves in “Evolution Canyon”. Finally, the paper briefly reviews the remarkable interslope incipient sympatric speciation ofH. spontaneumat “Evolution Canyon”, as is true for other organisms such as bacteria,Drosophila, and spiny mice,Acomys. Sympatric ecological speciation is still controversial and “Evolution Canyon” provides an appropriate site to explore it inH. spontaneumand other organisms across life.