They are sometimes identified as a subspecies with the scientific name Bos taurus africanus. Dairy cows generally are of the species "Bos taurus". The first domestication event occurred around 10,500 years ago with the evolution of "Bos taurus". A bull is an intact (i.e., not castrated) adult male of the species "Bos taurus". They identified eight proteins from the genus "Bos taurus" indicative of calf tissue. The complete sequence and modular organization of SCO-spondin was first characterized in Bos taurus. It has been crossbred extensively with "Bos taurus taurus" (European) beef breeds of cattle.