In the third millennium B.C.E., a strange group of donkeylike creatures was buried alongside royals in an ancient city east of what is now Aleppo, Syria. Archaeologists reckoned the animals were “kungas,” a rare type of ass highly prized by Bronze Age Mesopotamian elites. Yet their true biological identity has remained a mystery. Now, a genetic study of the bones reveals the enigmatic beast was the offspring of a female donkey with a male wild ass, making it the first humanmade hybrid documented in the archaeological record.
“This is the answer to a long-held question” of the kunga’s identity, says Benjamin Arbuckle, a zooarchaeologist at the University of North Carolina, Chapel Hill, who was not part of the study. “Finally having this confirmation from the bones is incredible,” adds Laerke Recht, a zooarchaeologist at the University of Graz who also was not involved.
By 3000 B.C.E., several types of donkeys and related animals roamed the Near and Middle East, including the Syrian wild ass and the domesticated donkey. Horses weren’t widely adopted in the region until the following millennium, so their stockier cousins played essential roles in agriculture, transportation, and warfare in the ancient kingdoms of Syria.
Cuneiform clay tablets from the era recount one uncommon donkey type, the strong and stocky kunga, as the favorite of the region’s rich and powerful. The texts describe complex animal husbandry programs devoted to breeding kungas from two separate species of equid, but they don’t detail what those species were and whether the resulting offspring was sterile. There’s some indication that kungas were faster than the average ass, but the texts don’t reveal why the animals were so valuable, Arbuckle says.
When archaeologists excavated the 4500-year-old royal burial compound at the Aleppo site, known as Umm el-Marra, in 2006, a group of donkey bones stood out. They didn’t look like they came from a known species, but it’s tricky to identify equids from just the remains, Recht explains. “Even bones of horses and donkeys can be hard to distinguish.”
From the placement and positioning of the burials, archaeologists thought the creatures might be the mythic kungas. They were interred as individuals, a rarity in the archaeological record as animal remains are usually simply thrown away. Many of the beasts also appear to have been sacrificed, presumably to join their humans in the afterlife.
“These animals must have been very special,” says Eva-Maria Geigl, a geneticist at the Jacques Monod Institute in Paris. Archaeologists brought the remains to Geigl and her collaborators in hopes of identifying them.
The genetic material in the skeletons was poorly preserved after thousands of years baking in the Syrian desert. “The bones were like chalk,” Geigl says. So the team used highly sensitive sequencing methods to analyze nuclear DNA from the remains, while also looking at regions from the animal’s maternal and paternal lineages. They compared the possible kunga DNA to the genomes of other equids, including modern horses, domestic donkeys, and the extinct Syrian wild ass.
The bones weren’t from a single species of equid, the researchers report today in Science Advances. Rather, the animal was the first generation offspring of two species, a female domestic donkey and a male Syrian wild ass.
Although the human breeders of the first domesticated animals must have repeatedly crossed them with their wild cousins, this is the first documented example of a half-wild, half-domesticated animal. The mule (a hybrid of horse and donkey) is possibly the next-earliest such beast, but it didn’t come onto the scene until later. Geigl and her colleagues previously documented horse-donkey hybrids from an ancient settlement in modern-day Turkey dating to about 1000 B.C.E., more than 1000 years after the Umm el-Marra kungas were buried.
The new results underscore the technical capabilities of Bronze Age Mesopotamian societies, the researchers say. Capturing wild animals to breed with donkeys was likely complicated (Syrian asses are notoriously ornery), especially at the widespread scale described in the cuneiform texts.
What’s more, the breeders’ choice of the mother as the domestic animal reveals the sophistication of their mating scheme. Domesticated donkeys are easier to keep in captivity as they raise offspring, says Thierry Grange, a geneticist who led the research with Geigl and is also at the Jacques Monod Institute.
Arbuckle agrees. “This is a great example that shows the level of organization and management techniques needed to keep these animals alive,” he says. “It’s very much like modern zoo management.”
Geigl thinks it’s likely that humans were crossing donkeys and related animals earlier in the Near East for farming and battle. And Recht says kunga bones have likely been misidentified as donkeys or asses at other previously excavated sites and are worth testing genetically now that researchers know what to look for. “I think we’ve missed a lot in the archaeological record.”