In ancient Mesopotamia 4,500 years ago, long before horses arrived in the region, another spirited member of the equine family, the kunga, played a prominent role pulling four-wheeled carts in fight.
Archaeologists had suspected that these animals – depicted in art, their sales recorded in cuneiform script, their bodies sometimes interred in rich burial grounds – were the result of some kind of interbreeding. But the evidence was lacking.
A team of researchers reported on more than a decade of research in the journal Science Advances on Friday, concluding that ancient DNA studies have shown the kunga to be a cross between a female donkey (Equus Africanus asinus) and a Male Syrian wild ass (Equus hemionus hemippus).
The kunga is the earliest known example of a man-made hybrid of two species, a production well beyond traditional animal domestication processes, the researchers found.
Eva-Maria Geigl, a specialist in ancient genomes at the University of Paris and one of the scientists who carried out the study, said kungas breeding was really “early bio-engineering” that developed into a kind of old biotechnology industry.
Like mules, which are hybrids between horses and donkeys, and which were created much later, kungas were sterile. Each new kunga was unique, a mating between a wild donkey stallion and a donkey.
Stallions had to be captured and kept in captivity, even though they were very aggressive, as modern records indicate. Dr Geigl said the director of a zoo in Austria, where the last captive Syrian wild donkeys died, described them as “furious”. Archaeological records show that a breeding center in Nagar (now Tell Brak, Syria) shipped young kungas to other cities. They were expensive animals, status symbols and were used in war and military ceremonies.
The Kungas have maintained their high status for at least 500 years, Dr Geigl said. Horses only appeared about 4,000 years ago to take their place in battles and ceremonies and to help create other hybrids. Prior to current research, the oldest known hybrid was a mule from a site in Turkey dating to 3,000 years ago. Members of the same team reported on this finding in 2020.
The research team had to contend with the very poor preservation of fossils from desert areas, but used a variety of techniques to examine ancient DNA. Laurent Frantz, a paleogenomics expert at the Ludwig Maximilian University of Munich, who was not involved in the study, said that despite these difficulties, the “results were very convincing”, showing that people were “experimenting with hybrid equines long before the arrival of the horse.”
Fiona Marshall, an archaeologist at Washington University in St. Louis who has researched the prehistory of donkeys and their domestication, said the study was “hugely significant” in part because it showed herders had clear intentions. The early process of domestication has always been murky — probably partly accidental, partly human intervention — but this research has shown what the ancient Syrians were looking for.
“People wanted the qualities of a wild animal,” she said. Donkeys may have been more docile than their ancestors, the African wild ass, but herders in Mesopotamia wanted to breed with other wild asses for strength and speed – and perhaps size. Although the last known living examples of the Syrian wild ass were very small, just over a meter at the shoulder, older animals of the same species were larger.
Dr Geigl – who collaborated on research with Thierry Grange at the University of Paris, E. Andrew Bennett, now with the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, Jill Weber at the Museum of Archeology and Anthropology from the University of Pennsylvania and others – said the team sequenced DNA from many sources, including modern donkeys, horses and several species of wild ass, as well as museum samples.
The bones of 44 kungas buried in a rich burial site in Syria called Umm el-Marra were of particular significance. These skeletons had previously led Dr. Weber and others to speculate that they were hybrids and that they were the kungas described in the tablets and depicted in art.
Their teeth showed bite marks and indicated that they had been on a special diet. The new research used the DNA of these kungas to compare them to other species and determine that these animals were, as suspected, the result of breeding female donkeys and male Syrian wild ass.
The research team also sequenced the DNA of a Syrian wild ass found at Gobekli Tepe in Turkey, an 11,000-year-old site where humans gathered for purposes still being studied, and two of the last animals of the species, kept in a zoo in Vienna.
It is a species that no longer exists. Kunga cannot be recreated, Dr. Bennett said. Donkeys are plentiful, of course, but the last known Syrian wild donkeys died in the late 1920s. One was shot in the wild and the other died in a Vienna zoo.
“The recipe for making kunga was unknown for thousands of years,” Dr. Bennett said. “And we finally decode it not even 100 years after one element disappeared.”