It has been considered that the donkey was domesticated 6,000 years ago, from the African wild ass (Equus asinus), in northeastern Africa, to which it still bears a great resemblance, including the shoulders' "cross" (the wild donkeys of southwestern US and other areas are just feral bewildered animals).

But a new research published in the "Proceedings of the National Academy of Sciences" shows that donkey domestication is a far more complex process. The research team has discovered proofs of the earliest transport use of the donkey and the early stages of donkey domestication, which appear to have been slower and more complex than previously believed.
The team investigated 10 donkey skeletons from three 5,000-year-old tombs dedicated to donkeys in the funerary complex of one of the first Pharaoh at Abydos (Egypt).

The animals appeared to be in the incipient stages of domestication: these donkeys resembled wild asses, but their joint wear clearly indicated they were employed as burden animals.

"Genetic research has suggested African origins for the donkey. But coming up with an exact time and location for domestication is difficult because signs of early domestication can be hard to see. Our findings show that traces of human management can indicate domestication before skeletal or even genetic changes," said lead researched Dr. Fiona Marshall, professor of Anthropology at Washington University in St. Louis.

Today, we associate Northern Africa and Middle East to camels, but the historic role of the donkey was much higher in the centuries before the Christian era, as the camels spread in the area from Arabia only about 2,000 years ago.

Donkeys contributed to the boom of ancient goods transport systems in Africa and western Asia and also to the development of the ancient cities and pastoral societies. The first caravans crossing Sahara included donkeys.

The team compared the Abydos skeletons to 53 modern-day donkey and African wild ass skeletons. The Abydos metacarpal bones (on the lower forelimbs) had the same proportions like in the wild ass, but individuals of domesticated donkeys varied more in their size than the wild animals. Mid-shaft breadths were similar to the wild ass, but mid-shaft depths and distal breadths were intermediate between the wild ass and the domestic donkey.

Still, all the Abydos skeletons displayed wear and other bone pathologies connected to load carrying. Overall, the bone morphology indicates that 5,000-year-old Egyptian donkeys were still experiencing significant phenotypic change towards the modern-day donkeys. These results sustain other researches showing that domestication is a slower and more complex process that we previously believed.