Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Evidence for two independent domestications of cattle.

Abstract

The origin and taxonomic status of domesticated cattle are controversial. Zebu and taurine breeds are differentiated primarily by the presence or absence of a hump and have been recognized as separate species (Bos indicus and Bos taurus). However, the most widely held the view is that both types of cattle derive from a single domestication event 8000-10 000 years ago. Mitochondrial DNA (mtDNA) sequences from representatives of 6 European (taurine) breeds, 3 Indian (zebu) breeds and 4 African (3 zebu and 1 taurine) breeds were studied. Similar levels of average sequence divergence were observed among animals within each of the major continental groups: European, 0.14%; African, 0.38%; Indian, 0.42%. However, the sequences fell into 2 very distinct geographic lineages that do not correspond with the taurine-zebu dichotomy: all European and African breeds are in one lineage, and all Indian breeds are in the other. There was little indication of breed clustering within either lineage. Application of a molecular clock suggested that the 2 major mtDNA clades diverged at least 200 000 and possibly as much as 1 million years ago. This relatively large divergence is interpreted most simply as evidence for 2 separate domestication events, presumably of different subspecies of the aurochs, Bos primigenius. The clustering of all African zebu mtDNA sequences with the taurine lineage is attributed to ancestral crossbreeding with the earlier B. taurus inhabitants of the continent.