Taming horses

The importance of the domestication of horses to human civilisations is undisputed. But there are conflicting hypotheses about the origins of tamed horses; the 'restricted origin' hypothesis postulates selective breeding of a few founding lineages followed by distribution, while the 'multiple origins hypothesis' suggests independent recruitment of a large number of founders over an extended time period and geographical location. In the January 19 Science, Vila et al. describe genetic analysis that provides support for the latter theory (Science 2001, 291:474-477). They performed phylogenetic analysis of 37 different mitochondrial DNA (mtDNA) control sequences from domesticated horses and calculated a mean divergence of 2.6%, suggesting that these sequences stem from ancient origins. They sequenced mtDNA segments in 191 horses from 10 distinct breeds and compared modern horses with ancient DNA from archaeological sites. Some of the ancient horses are distributed throughout the tree defined by modern horse...