For thousands of years, donkeys have been critical for propelling human civilizations forward. They’ve helped pull wheeled vehicles, carry travelers and move goods across the world.
But where and when these animals first became intertwined with humans has been a mystery. Now, researchers have used the genomes of over 200 donkeys to trace their domestication back to a single event around 7,000 years ago in East Africa—about 3,000 years before humans tamed horses. The team published their findings, which detail the donkey’s history, in the journal Science this month.
“Through their DNA, the animals are telling their history themselves,” co-author Samantha Brooks, an equine researcher at the University of Florida, says in a statement. “We usually only get the human’s side of history through written accounts, but of course written history does not always record exactly how something happened. Looking at these DNA sequences, we get a biological testimony to the environment these animals lived in and the experiences they survived.”
The researchers examined 207 genomes from modern donkeys living in 31 countries across the globe. They also looked at genomes from 15 wild equids and 31 earlier donkeys that lived between about 4,000 and 100 years ago. The team reconstructed the animals’ evolutionary tree and used computer models to pinpoint the domestication event, when herders in Kenya and the Horn of Africa tamed wild asses. They then traced how the animals spread across the rest of the continent and into Europe and Asia about 2,500 years later.
“This is the story of the donkeys… and the detail is amazing,” Greger Larson, an evolutionary biologist at the University of Oxford in England who was not involved with the study, tells Science’s Elizabeth Pennisi. “I’m pleased to see the donkey finally getting his day.”
The findings revealed other bits of the animal's history: For example, at what appears to have been a donkey breeding center in an ancient Roman villa located in northeastern France, humans bred African and European donkeys together to create “giant donkeys,” Science writes. These animals were nearly 10 inches taller than a standard donkey.
Though it’s still unclear why the original domestication happened, Science News’ Freda Kreier reports that the event coincided with the Sahara growing larger and more arid.
“Donkeys are champions when it comes to carrying stuff and are good at going through deserts,” co-author Ludovic Orlando, an evolutionary biologist at Paul Sabatier University in France, tells the publication. Prehistoric humans may have enlisted donkeys’ help in navigating the expanding Sahara.
Researchers say these findings could help put donkeys in the spotlight, per Science News. The animals could benefit from more research: Currently, there are no published genomes from donkeys located south of the equator in Africa. But understanding where the animals were first domesticated could guide archaeologists to a narrower region to search for insights about the original tamed donkeys, per the publication.
Not only does understanding the equines’ genetic makeup help reveal their contributions to human history, but it also might improve their management in the future, as climate change alters the planet’s environment, write the authors. Currently, about 50 million donkeys live on Earth, and they remain important for agriculture and transportation.
“Donkeys are extraordinary working animals that are essential to the livelihoods of millions of people around the globe,” Emily Clark, a livestock geneticist at the University of Edinburgh in Scotland who was not involved in the study, tells Science News. “As humans, we owe a debt of gratitude to the domestic donkey for the role they play and have played in shaping society.”