Credit: Stine Rossel/PNAS
One of the markers of domestication is a reduction in size, but archeological evidence indicates size decreases were slow and inconsistent. Donkeys buried 5,000 years ago in an early pharaonic mortuary complex (above) have proportions similar to those of the African wild ass, but the bones of domesticated donkeys found at another, much older site are significantly smaller than those of wild asses.