(CN) — Scientists announced Friday they have used genome sequencing to uncover the earliest known evidence of humans breeding hybrid animals.
According to research published in the journal Science Advances, researchers determined that 4,500-year-old skeletons from the horse family found buried in modern-day northern Syria are most likely domesticated hybrid animals called kungas that can be traced to the Bronze Age of Mesopotamia.
The research indicates the people were breeding kungas more than 500 years before the first domestic horses were introduced to the area. Crosses between domesticated female donkeys and male Syrian wild asses, kungas have long been at the center of debate among specialists.
“We have a pretty good answer to a debate that lasted for decades,” said Eva-Maria Geigl, one of the paper’s authors from the Institut Jacques Monod in France. “These are the most ancient human-made hybrids that we know.”
Geigl said kungas are documented as a distinct animal on ancient tablets and seals dating back to 2500 BC, often with four of them pulling warriors to war in wagons. Researchers knew the animals depicted were not horses because the domestic horses were not yet in the area and the drawings showed tails like that of a donkey.
According to Geigl, the tablets show the kungas were “very valuable and expensive animals.” They were given as gifts to royalty and cost up to six times the price of a donkey. The skeletons used in the research come from an ancient burial site in modern-day northern Syria, where the elite were buried with their valuables. In the same cemetery, there were 44 whole skeletons of the animals.
“This is really surprising, because normally you eat animals and throw them in the waste. You do not find entire skeletons,” Geigl said. “This means that people at the time buried entire animals, so these animals must have been very special and precious.”
Geigl said she and her colleagues approached archaeologists with research on Asiatic wild asses, a distant relative of the donkey. The Asiatic wild asses are difficult to domesticate, highly aggressive and extremely fast.
“We studied these animals that are very poorly known,” Geigl said, noting that their scientific name Equus hemionus is often confused for a character from Harry Potter. She added there are “very few of them left,” with only modest wild populations remaining in Iran, Turkmenistan, Mongolia and Tibet.
She said the Syrian subspecies is extinct, with some of the last individuals put into zoos at the beginning of the 20th century, where they were described by the zoo director.
“He was fascinated by these animals because they were extremely aggressive, extremely hot-tempered,” Geigl said. “They were furious, they would destroy anything — including themselves — because they did not accept this captivity.”
Using measurements, researchers knew that the ancient bones found at the site in Syria were neither donkeys nor a subspecies of Asiatic wild ass and could be the kungas described on the ancient tablets. Geigl said the teeth of the skeletons provided crucial clues to their identity.
The teeth displayed no signs of feeding on shrubs, leaves or fruits, suggesting the animals were fed. Further, their cheek teeth indicated that the animals wore a bit in their mouths like what horses today wear while riding.
The researchers then turned to DNA. Targeting the mitochondrial DNA, they verified that the mother of the skeletons was a domesticated donkey. The Y chromosome DNA suggested the father was related to the Asiatic wild asses, but the limited knowledge of the Asiatic wild asses and the Syrian skeletons’ poor quality of preservation made it difficult to conclude whether the animals came directly from the mating of a domesticated donkey and a subspecies of the Asiatic wild ass.
“The bones were like chalk and the DNA was poorly preserved because it’s too hot there,” Geigl said.
With the genomic revolution of the 2010s, Geigl said they worked hard to do genome sequencing on the ancient skeletons from Syria and the last specimens of the Syrian wild asses that died in captivity in the early 1900s and were then preserved in the Natural History Museum of Vienna. With this, researchers determined the paternity of the skeletons was indeed directly from a Syrian wild ass.
“This means that this was a first-generation hybrid,” Geigl said, noting that the kungas are the earliest known example of hybrid animals bred by humans.
She said the people of ancient Mesopotamia had to capture Syrian wild asses in the desert each time they wanted to make a kunga, since ancient tablets indicate the kunga offspring themselves were sterile – not unusual for hybrids in the horse family. Geigl said in the 1930s, the Russians bred donkeys with the surviving Asiatic wild asses in Mongolia. The offspring were “healthy and robust, but sterile.”
The effort and strategy required to catch the fast and aggressive Syrian wild asses suggests why the kunga were such a treasured commodity at the time.
“There was one city in the north of Syria that was famous for producing mass kungas and exporting them to the other cities,” Geigl said. She added thar records show the wild asses were still being captured in 600 BC, by then using domesticated horses and lassos.
Going forward, Geigl said she and other researchers want to further explore how widespread and diverse the practices of breeding were in the ancient civilization.
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