Barley is thought to have been domesticated from its wild progenitor (Hordeum vulgare ssp spontaneum) around 10,000 BC. Archeological remains have found the progenitor associated with human habitation and probably cultivation from around 23,000 years ago so humans have been utilising the domesticated form for a shorter period than the non-domesticated. The principal event facilitating barley domestication was the change from a brittle or shattering rachis to a non-brittle type that retained the grain on the ear and thus made the crop much easier to harvest and store. There are two closely linked dominant complementary genes (Btr1 and Btr2) controlling rachis shattering and independent mutations in each have led to the non-shattering form. The genes have recently been identified and analysed to reveal that European and West-Asian barleys tend to have the mutant non-shattering allele in the first gene (Btr1) and East Asian types in the second gene (Btr2) . Therefore, the F1 hybrid seed of crosses made between the two different types will have a brittle rachis and subsequent generations will be a mixture of shattering and non-shattering types.