Genetic analysis proves that the African wild ass, which may be down to the last few hundred individuals, is the ancestor of modern donkeys. The same study by an international group of researchers suggests that a subspecies, the Nubian wild ass, thought to have vanished, might have survived after all.
The critically endangered African wild ass–which today exists only in small numbers in eastern Africa, zoos, and wildlife preserves–is the living ancestor of the modern donkey, according to the University of Florida (UF).
NGS stock photo of modern donkey by Jodi Cobb
Donkeys were domesticated by mobile, pastoral people who had to recruit animals to help them survive the harsh Saharan landscape in northern Africa more than 5,000 years ago, say scientists who published their findings this week in Proceedings of the Royal Society B.
The discovery by an international research team paints “a surprising picture of what small, isolated groups of people were able to accomplish when confronted with unpredictable storms and expanding desert,” UF says in a news release about the study.
“It says those early people were quite innovative, more so than many people today give them credit for,” says Connie Mulligan, UF associate professor of anthropology.
“Domestication happened first in northern Africa and happened there more than once.”
“The domestication of a wild animal was quite an intellectual breakthrough, and we have provided solid evidence that donkey domestication happened first in northern Africa and happened there more than once.”
NGS stock photo of donkey in Jordan by James L. Stanfield
NGS stock photo of donkey in Morocco by James L. Stanfield
Researchers sorted through the most comprehensive sampling of mitochondrial DNA ever assembled from ancient, historic, and living specimens to make the ancestral connection, Mulligan says.
“What’s more, researchers found evidence to suggest that a subspecies called the Nubian wild ass, presumed vanished late in the 20th century, is not only a direct ancestor of the donkey–it may still exist,” UF added.
“The ancestors of the domestic donkey were considered vital for collecting water, moving desert households, and creating the first land-based trade routes between the ancient Egyptians and the Sumerians,” according to study co-author Fiona Marshall, a professor of anthropology at Washington University in St. Louis.
NGS stock photo of donkeys by Ira S. Lerner
An Old World prehistorian, Marshall has documented evidence of the donkey’s domestic service by looking at skeletal wear and tear of animal remains found entombed near Egyptian pharaohs.
Scientists traced the family trees of the domestic donkey using samples from living animals, skeletons of African wild ass held in museums worldwide and isolated donkey bones from African archaeological sites.
Steam engines of their day
“These were the first transport animals, the steam engines of their day,” Marshall says. “Today domestic donkeys are often conceived of as animals of poor people, and little is known about their breeding. This is the first study to determine the African wild ass, which includes the Nubian strain, is the ancestor of the domestic donkey. That’s important to know for efforts to preserve the species.”
NGS stock photo of donkeys in Iran by J. Baylor Roberts
There are small numbers of the Somali subspecies of the African wild ass in zoos and wildlife preserves, and about 600 still exist in the wild in Eritrea and Ethiopia, but the Nubian subspecies was last seen in the Red Sea Hills of Sudan late in the 20th century, according to the scientists.
“Hope for its continued existence springs from a sample collected in northern Africa in the mid-1990s by co-author and biologist Albano Beja-Pereira of the University of Porto, Portugal,” UF says.
Reintroducing Nubian ass to the wild
“If any Nubian survivors are found, the possibility remains that the animals could be bred and reintroduced into the wild. The evidence reinforces the need for surveys and wildlife management plans in eastern Sudan and northern Eritrea,” the researchers say.
“The whole idea behind conservation is the need to maintain genetic variation,” Mulligan says. “We don’t know which elements are more or less important, but we think the whole range of diversity is important to the health of the species. Knowing the genetic makeup of the animals is essential to protect that diversity.”
In addition, placing the domestication of the donkey in northern Africa helps scientists better understand the archaeological record and early culture of the area, the researchers add.
“Knowing where a domestication event first occurred is important, because there are always cultural ramifications from being first,” explains Sandra Olsen, curator of anthropology at the Carnegie Museum of Natural History in Pittsburgh, who did not participate in the research.
“With a nucleus of animals that can serve as either a food source, transportation, or some other purpose, particular cultures acquire advantages that make them more successful than their neighbors. Consider that animals like the horse and the donkey were used for military purposes.
“From the point of view of a biologist or someone who studies animal husbandry, it is interesting to find the source for a species because it can even have veterinary ramifications,” she says.
“The work done in this project is extraordinary. They located very hard to find samples not common at all in museums, and the archeological specimens are difficult to obtain positive results from because the heat often destroys the organic material. They’ve made some considerable advances.”
Somali wild ass is not a living ancestor
Besides revealing that the African wild ass is the living ancestor of today’s domestic donkeys, the genetic evidence also reveals that the Somali wild ass is not a living ancestor as once suspected, but closer akin to a more modern cousin, UF said.
“That leaves a question of a remaining, yet unidentified ancestor of modern donkeys believed to have sprung from a different branch of the family. Researchers suspect that ancestors of this animal are extinct, but they may have roamed the Maghreb of northeastern Africa, and possibly the coast of Yemen.”
NGS stock photo of donkey and rider on Zanzibar, Tanzania by W. Robert Moore
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species lists the African wild ass (Equus africanus) as Critically Endangered as the species “numbers at best approximately 200 mature individuals.”
The wild ass may be undergoing a continuing decline due to climate and human/livestock impact, and no subpopulation numbers in excess of 50 mature individuals, IUCN explains on its website. “The total number of observed African wild ass in Eritrea and Ethiopia is 70 individuals; there may be as many as 600 individuals in these two countries, but this figure is a very rough extrapolation from more intensely studied areas.”
In Ethiopia, in the last 35 years there has been a greater that 95 percent population decline and in the last 12 years the African wild ass has been extirpated from roughly 50 percent of its range, added IUCN. In Eritrea, the population is stable and slowly increasing. “However, it is difficult to predict population trends into the future. The desert habitat of the African Wild Ass in both Eritrea and Ethiopia suffers from recurrent and extreme droughts.”
Ironically in the light of this week’s research announcement, a major threat to the survival of the African wild ass, according to IUCN, is possible interbreeding with the domestic donkey.
Other threats include hunting for food and medicinal purposes, (for example, body parts and soup made from bones are used for treating tuberculosis, constipation, rheumatism, backache, and boneache), and limited access to drinking water and forage (largely due to competition with livestock).
Posted by David Braun from media material provided by the University of Florida.
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