From pulling Mesopotamian war chariots to grinding grain in the Middle Ages, donkeys have carried civilization on their backs for centuries. DNA has now revealed how old the relationship between humans and donkeys really is.
Genetic instruction books for more than 200 donkeys from countries around the world show that these beasts of burden they were domesticated about 7,000 years ago in East Africaresearchers report in the Sept. 9 issue Sciences.
“The donkey story has baffled scientists for years,” says Ludovic Orlando, a molecular archaeologist at the Toulouse Center for Anthropobiology and Genomics in France. This discovery shows that donkeys were domesticated at one time, approximately 3,000 years before horses.
DNA has great potential to unravel humanity’s shared history with our fellow animals. In 2021, Orlando and his colleagues DNA used from horse bones to trace its domestication in the Eurasian steppes, in what is now southwestern Russia, to more than 4,200 years ago (Serial number: 10/20/21).
But the story of the donkeys (Equus asinus) had remained cloudy. Today, domesticated donkeys are found throughout the world. A declining number of wild asses in Asia and Africa, the donkey’s closest wild relatives, pointed to one of those continents as the donkey’s likely homeland.
Archaeological evidence, including a 5,000-year-old Egyptian tablet showing marching donkeys, sheep and cattle, focused on Africa as the most likely contender. But genetic studies trying to pin down when and where donkeys were domesticated have been largely inconclusive.
This was likely because scientists were missing donkey DNA from many regions of the world, says Orlando. For example, to date, no genomes of donkeys living south of the equator in Africa have been published. To get a broader diversity of DNA, Orlando and his colleagues pooled 207 donkey genomes that lived in 31 countries, from Brazil to China, along with DNA from 31 donkeys that lived between 4,000 and 100 years ago.
By comparing these genomes to those of wild asses, the researchers found that all donkeys could trace their lineage back to a single domestication event in East Africa, perhaps the Horn of Africa, around 5,000 BCE. C. From there, domesticated donkeys spread to the rest of the continent and in Europe and Asia, where they formed genetically distinct groups depending on the region. Humans have now brought donkeys to nearly every continent on Earth, carrying their genetic legacy with them.
These results add new clarity to the story of donkey domestication, says Emily Clark, a livestock geneticist at the University of Edinburgh’s Roslin Institute. “Donkeys are extraordinary working animals that are essential to the livelihoods of millions of people around the world,” she says. “As humans, we owe a debt of gratitude to domestic donkeys for the role they play and have played in shaping society.”
Exactly why people chose to domesticate wild asses in Africa thousands of years ago is unclear. But the timing of their first expansion into East Africa coincides with a period when Sahara began to become more arid and enlarged (Serial number: 8/5/08).
“Donkeys are champions when it comes to carrying things and are good at traversing deserts,” says Orlando. As the desert grew, the donkeys may have provided much-needed help moving goods through the increasingly dry terrain, he says.
The archaeological record of donkeys in Africa outside of Egypt is scant. The new result could help archaeologists narrow their search to new areas to learn more about the first donkeys and the people who domesticated them, says Orlando.
Meanwhile, delving into the genetic diversity that has enabled donkeys to support human endeavors in a variety of environmental conditions could put donkeys in the spotlight as climate change exacerbates droughts and threatens to expand the deserts around the world (Serial number: 03/10/22).
“Donkeys still provide a lot of support to people living in low- and middle-income countries,” says Orlando. Understanding humanity’s shared history with donkeys “isn’t just about the past, it could actually be useful in the future.”