It is theorized that wheat's ancestors (Triticum monococcum, Aegilops speltoides, and Aegilops tauschii, all diploid grasses) hybridized naturally over millennia somewhere in West Asia, to create natural polyploid hybrids, the best known of which are common wheat and durum wheat.
Hexaploid wheats (e.g. T. aestivum and T. spelta) are the result of a hybridisation between a domesticated tetraploid wheat, probably T. dicoccum or T. durum, and another goatgrass, Ae. tauschii (also known as Ae. squarrosa).