THEY may not have known about genes and Darwinism, but our ancestors knew how to drive the evolution of once-wild beasts to serve their own needs. A spate of studies published last week show how domestication suddenly gave horses coats of many colours, cows the extra genes to produce milk and fight infection 鈥� and even shrank sheep鈥檚 horns.
The studies also support what archaeologists have long argued about the domestication of wild beasts: that sheep were probably the first farmed animals, about 11,000 years ago, followed by cattle. Then, around 5500 years ago humans tamed horses, giving riders hitherto unmatched military might, speed and mobility. 鈥淚t was a huge innovation,鈥� says Arne Ludwig of the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany.
Ludwig led a team which analysed six genes linked with coat colour in 89 horse fossils, originating from 40,000 years ago to the Middle Ages, which were collected from sites ranging from Spain to China.
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The genetic analysis revealed that before about 5500 years ago, almost all horses had reddish-brown or black coats (Science, ). Then, in what is now Ukraine, Romania and Russia, there was an explosion in colour when humans tamed horses and bred animals with a new range of coat colours, from chestnut to cream, white and dappled.
Our impact on the ancestors of sheep was no less dramatic, show several studies, including one led by of the University of Glasgow in the UK. By analysing harmless 鈥渟towaway viruses鈥� in the genetic material of sheep, Palmarini鈥檚 team was able to distinguish ancient from modern breeds (Science, ).
They found that sheep were domesticated in two waves. Examples of the first wave still survive as semi-wild breeds, such as the shaggy Soay and Orkney breeds on Scottish islands. The second wave started about 6000 years ago, when farmers in what is now Iraq and Iran began selecting for characteristics such as reduced moulting and smaller horns. Their more ancient, shaggier counterparts were exiled to the fringes of Europe, where they became semi-wild again.
Also, the first analyses of the entire cow genome show that with domestication came a big spurt in the diversity of genes linked with milk production, musculature and immunity to bacterial infection (Science, and ). 鈥淭here are several areas of the genome you can see that clearly differentiate between beef breeds and dairy breeds,鈥� says of the University of Illinois at Urbana-Champaign, who leads the international cow-genome sequencing project.
鈥淎reas of the cow genome clearly differentiate between beef breeds and dairy breeds鈥�
