In a new study, genetics and archaeology combine to reveal the ancient origins of humanity’s first beast of burden.
By Franz Lidz – Photographs by Samuel Aranda – Science – 14 March
“The donkey is a key, if increasingly marginalized, character in human history. Once venerated, the animal has been an object of ridicule for so long that the word “asinine” — derived from the Latin asinus, meaning “like an ass or a donkey” — means “stupid.” Donkeys and donkey work are essential to the livelihoods of people in developing countries, but elsewhere donkeys have all but disappeared.
“I guess that we simply forgot the importance of this animal, probably being blown away by the impact of its close cousin, the horse,” said Ludovic Orlando, director of the Center for Anthropobiology and Genomics of Toulouse in France. “In Europe, the horse provided fast mobility and helped grow crops and make war. I am not sure we can claim that the impact of the donkey was as large.” Compared to horses and dogs, donkeys have received relatively little attention from archaeologists, much less geneticists.
Nonetheless, despite this being the Year of the Rabbit according to the Chinese zodiac, it might just be the Year of the Donkey. The Oscar-nominated film “EO” features as its hero a soulful, barbarously misused donkey. And donkeys star in a major new genetic study published in the journal Science; Peter Mitchell, an archaeologist at Oxford who was not involved in the project, called it “the most comprehensive study of donkey genomics yet.”
Dr. Orlando, who has spent years mapping the domestication history of horses, is an author of the paper, which he hopes will jump-start research on the humble donkey and restore some of its dignity. He and researchers from 37 laboratories around the world analyzed the genomes of 207 modern donkeys, living in 31 countries. They also sequenced DNA from the skeletons of 31 early donkeys, some of which date as far back as 4,500 years.
Scholars had previously identified three potential centers of domestication, in the Near East, northeast Africa (including Egypt) and the Arabian Peninsula. But Dr. Orlando’s team concluded that donkeys — humanity’s first land-based transport — were domesticated only once, around 5,000 B.C., when herders in the Horn of Africa and present-day Kenya began to tame wild asses. That date is about 400 years before the earliest archaeological evidence of tamed donkeys from El Omari, near Cairo, and nearly three millenniums before horses were first harnessed.
The period coincided with one where the Sahara grew larger and more arid. Donkeys are especially resistant to drought and tolerant to water deprivation, which has led Dr. Orlando to speculate that they became an indispensable conveyance for herders and their wares. “Finding an auxiliary for transportation in those increasingly difficult conditions probably triggered the domestication process,” he said.
From that point of origin in northeastern Africa, the team then reconstructed the evolutionary tree of donkeys and traced their dispersal routes across the rest of the continent. Donkeys were traded northwest into today’s Sudan and onward into Egypt, trotting out of Africa around 5,000 years ago, and splitting off to Asia and Europe some 500 years later. The various donkey populations became progressively isolated by their geographic distance, even though trade resulted in systematic shifts back to Africa. Interbreeding between bloodlines was limited.
A 2004 study, examining a small sample of modern DNA from hundreds of donkeys, had suggested that humans domesticated wild asses twice, in Africa and Asia. The lead researcher, Albano Beja-Pereira, a geneticist at the University of Porto in Portugal, collaborated with Dr. Orlando and his colleague Evelyn Todd to revisit the conclusions using a larger data set, and now agrees with the single domestication hypothesis.
To our ancestors, the donkey assumed an extremely varied mythical and religious dimension. In ancient Egypt, the ass was one of the sacred animals of Seth, the Lord of Chaos. In Greek folklore, a donkey — an equid involved in the harvest and production of wine — was the mount that carried the god Dionysus into battle against the Giants, and flutes fashioned from donkey tibiae (which produced a braying-like sound) were used in his worship.
Donkeys are central to Judaic, Christian and Muslim iconography: In the Old Testament, Balaam’s ass saw an angel and uttered prophecies. In the New Testament, Jesus entered Jerusalem on a donkey on the day that Christians celebrate as Palm Sunday. Ya’fur was the name of the donkey that the Prophet Muhammad is said to have ridden and conversed with.
During the Bronze Age, from 3300 B.C. to 1200 B.C., donkeys were sometimes buried with humans, indicating a bestowal of honor on both parties. “In other cases, we find them as ritual deposits below floors, as recently discovered at Tell es-Safi, or seemingly as buried in their own right,” said Laerke Recht, an archaeologist at the University of Graz in Austria who also worked on the new paper. She quoted a term that dates back to at least the second millennium B.C.: “to kill a donkey,” which means to sign a treaty, an act that apparently involved a sacrifice.
The new findings revealed a previously unknown lineage of donkeys present in the Levant from around 200 B.C. At an archaeological site on the grounds of a Roman villa in the French village of Boinville-en-Woëvre, 175 miles east of Paris, investigators found what seems to have been a donkey breeding center, where donkeys from western Africa were mated with their European counterparts. The resulting pack animals measured 61 inches, or 15 hands, from the ground to the withers. The current standard is 51 inches or 12 hands. The only comparable modern donkeys are the American Mammoth Jacks — large, robust males bred to produce draft mules or for agricultural work.
Dr. Orlando said that the production of giant-donkey bloodlines occurred at a time when mules — the sterile offspring of male donkeys, or jacks, and horse mares — were vital to the Roman economy and its military. “It wouldn’t take that many generations to selectively breed larger and larger donkeys,” said Dean Richardson, a professor of equine surgery at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center. “Giant jacks have always been in demand to make more valuable mules.”
It is likely that the Romans preferred mules for their stamina, their speed and their capacity to bear massive loads of goods, especially for the army, which was stretched over thousands of miles. “When the Roman Empire collapsed, there was no incentive left for transportation across those long roads, and societies turned to more local economies,” Dr. Orlando said. “The donkey then became more dominant and mules were hardly ever produced.”
How can you tell that an ancient donkey was broken-in? “Domestication is a process,” said Dr. Mitchell, the Oxford archaeologist and author of “The Donkey In Human History.” Two decades ago at Abydos, in southern Egypt, the skeletons of 10 donkeys, dating from 3100 B.C., were excavated outside the funerary enclosure of the first pharaohs. “The bones showed a clear mosaic of wild and domestic characteristics,” Dr. Mitchell said. “What gave away their domestic status was damage to vertebrae and joints consistent with hauling.”
He said that the paucity of donkey scholarship reflects the out-of-sight, out-of-mind view of Western scientists, since over the last century donkeys and mules have largely vanished from Europe and North America. “Even in the developing world, they are very much an animal associated with the poor and with women more than men — so there’s a double bias against them,” Dr. Mitchell said.
In his 2008 travelogue “The Wisdom of Donkeys,” the British academic Andy Merrifield notes that Benjamin, the skeptical donkey in George Orwell’s “Animal Farm,” desires only to retire to a pasture with his pal, a horse named Boxer. Dr. Merrifield finds in a donkey’s eyes “a touching sadness, a grace,” and a purity that “has no right to exist in the human world.”
Still, the lucrative trade in donkey skins, an often illegal, largely unregulated and expanding global industry, encourages intensive farming to harvest hides, which are boiled down to make ejiao, a gelatin used primarily in traditional Chinese medicines. “This goes so obviously against animal welfare and causes a threat to local donkey populations and to those who depend on this animal for their subsistence,” Dr. Orlando said. “If anything, our work reveals that our relationship with the animal goes really far back in time. This should help us realize the innumerable services they provided to humankind, and hopefully make us grateful.”