The ancient Egyptian state was built on the backs of tamed wild asses. Ten skeletons excavated from burial sites of the first Egyptian kings are the best evidence yet that modern-day donkeys emerged through domestication of African wild asses. The 5000-year-old bones also provide the earliest indications that asses were used for transport.
The skeletons suggest that the smaller frames of today's donkeys hadn't yet evolved. Instead, the bones resemble those of modern-day Nubian and Somali wild asses, which are much larger than today's donkeys.
Extensive wear on the joints of the excavated skeletons shows that the animals lived their lives transporting heavy loads. Cargoes may have included stone for a nearby temple at the excavation site in Abydos, 500 kilometres south of Cairo, as well as wine, grain and precious stones.
"This is the very dawn of the Egyptian state, the engine of which was the donkey," says Fiona Marshall of Washington University in St Louis, Missouri, US, a member of the research team.
The only anatomical signs of the transition from ass to donkey are changes in the metatarsal bone of the lower leg, which made the leg more compact – presumably an adaptation to cope with carrying loads.