LONDON (Reuters) - Horses were first domesticated on the plains of northern Kazakhstan some 5,500 years ago -- 1,000 years earlier than thought -- by people who rode them and drank their milk, researchers said on Thursday.

A mare is milked in a traditional village in northern Kazakhstan. REUTERS/Alan K. Outram/Handout

Taming horses changed human history, influencing everything from transport to agriculture to warfare. But experts have struggled to pinpoint when and where it first happened.

Now archaeologists think they have the answer, after finding the world’s oldest horse farm among the Kazakh people of the ancient Botai culture.

Remains of bones, teeth and shards of pottery, used to store mare’s milk, all indicate horses were selectively bred and exploited for domestic use east of the Ural mountains around 2,000 years before they are known to have been used in Europe.

Alan Outram from Britain’s University of Exeter said the new findings, published in the journal Science, changed understanding of how early societies developed.

“Once you have horse riding you’ve got much greater transport and trade capability, as well as potential advantages in warfare,” he said in a telephone interview.

“If it was happening this early, then you’ve got to think about those forces for social and economic change happening earlier too -- and it is possible that there are yet earlier sites we haven’t found.”

Archaeologists have suspected for some time that the Botai people were the world’s first horsemen but previous sketchy evidence has been disputed, with some arguing that the Botai simply hunted horses.

Now Outram and colleagues believe they have three conclusive pieces of evidence proving domestication.

They found that the leg bones of ancient Botai horses were similar to later Bronze Age domestic horses and very different from wild ones, suggesting breeding by humans.

They also identified clear markings on the horses’ teeth, indicating they wore bits or bridles, and finally an analysis of organic residues in broken pots found traces of horse milk.

Mare’s milk, usually fermented into a slightly alcoholic drink called “koumiss,” is still drunk in Kazakhstan.