Skip to main content
sdzglibrarybanner San Diego Zoo Global Library

African Wild Ass (Equus africanus) & Domesticated Donkey (Equus asinus) Fact Sheet: Taxonomy & History

Taxonomic History & Nomenclature

African wild ass

  • Equus africanus
    • Two (sometimes three) subspecies suggested (Moehlman 2002)
      • Somali
      • Nubian
      • (Saharan)

"Domestic donkey"

  • Equus asinus

How many kinds?

All African wild asses may actually be a single population with variation by geographic area.

  • Somali wild asses may actually be the only surviving African wild ass; they may be a sister group to domestic donkeys. (Groves and Ryder 2000)

Common Names

  • Domestic donkey, burro, or ass

Evolutionary History

Horses diverged from rhinos between 54 and 58 million years ago (Early Eocene) (Ryder 2009)

  • Horse lineages are called the hippomorphs; tapirs and rhinos are the ceratomorphs.

Most likely horses first dispersed from Europe to North America at the beginning of the Eocene. (Hooker 2008)

  • Pliolophus is now considered the earliest horse; it is closely related Hyracotherium from North America (Froehlich 2002) (Hooker 2008)
  • Pliolophus had four hooves on front limbs, three on rear, with short legs and was half the size of a fox terrier (Hooker 2008) (Agusti & Anton 2005)

The horse family, Equidae, has three main divisions based on anatomy and DNA studies. (Oakenfull et al 2000)

  • Caballines - include domestic horse and Equus przewalskii, a wild ancestor (Forstén 1988)
  • Asses - include domestic donkey, African wild asses, and the hemionines (Asiatic onager and kiang)
  • Zebras

The genus Equus appears around between 4 and 2 million years ago (Pliocene) (Oakenfull et al 2000) (Steiner & Ryder 2011)

A pony-sized horse, Hippidion, appeared in South America after the Isthmus of Panama formed about 3.2 million years ago (Orlando et al. 2009) (Weinstock et al. 2005)

  • Previous studies had suggeted these Hippidion lineages had more ancient orgins, around 10 million years ago
  • At least two South American species are recognized; one in high altitude Peru, another in Patagonia and Argentina
  • Equus dispersed from North America to Eurasia around 2.6 million years ago (Steiner & Ryder 2011)

The earliest known true African wild ass (E. africanus ) dates to 1.5 to 1.7 million years ago in Olduvai Gorge, Kenya. (Churcher 1982)

  • Domestic donkeys are descended from African wild asses (Clutton-Brock 1999)
  • Donkeys and closely related Asiatic asses have a long separate evolutionary history. (Forstén 1988,1989)

Recent genetic study of horse fossil DNA suggests that in North America there may be only two lineages of horses between 500,000 and 13,000 years ago (Weinstock et al 2005)

  • The "stilt-legged" lineage were small horses with slender legs built like modern onagers and kiang of Asia (but the African wild asses, not Asian asses, are considered the ancestors of modern donkey) (Beja-Pereira 2004)
  • The caballine lineage horses resembled modern horses and the nearly extinct Przewalskii horses; these horses diverged from each other around 250,000 years ago (Steiner & Ryder 2011)
  • Both lineages disappeared from North America by 13,000 years ago (but continued elsewhere)

Cultural History

According to archaeological finds, donkeys (burros) were domesticated about 5,000 years ago.(Rossel et al 2008)

  • Ten nearly complete donkey (E. asinus) skeletons carefully buried in tombs in Abydos, Egypt showed evidence of load-bearing and thus suggested that they had been domesticated. (Rossel et al 2008)

DNA analysis reveals that more than one distinct wild population of asses contributed genes to today's domestic donkey. (Beja-Pereira et al 2004)

  • Donkeys may be the only hoofed animal domesticated exclusively in Africa
    • African domestication happened during time when humans struggled to cope with development of the Sahara Desert some 5,000 to 7,000 years ago
  • Groves (1986), however, suggests original donkey domestication might be in the Middle East

Classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Perissodactyla (horses, tapirs, rhinos)

Suborder: Hippomorpha (horse-like mammals)

Family: Equidae (wild and domestic horses, donkeys, kiang, onager, zebras, extinct quagga)

Genus: Equus

Species: Equus asinus - domestic donkey (or burro, or ass)
Species: Equus africanus - African Wild Ass

Subspecies: Equus africanus africanus - Nubian Wild Ass
Subspecies: Equus africanus somaliensis - Somali Wild Ass

Describer (Date): Equus asinus: Linneaus 1758. Syst. Nat., 10th edition, 1:73. Equus africanus: Heuglin & Fitzinger 1866.

Page Citations

Agusti & Anton (2005)
Beja-Pereira et al (2004)
Bulletin of Zoological Nomenclature (2003)
Churcher (1982)
Clutton-Brock (1999)
Forstén (1988, 1989)
Froehlich (2002)
Groves (1986, 1995, 2002)
Groves & Ryder (2000)
Grubb (2005)
Hooker (2008)
Moehlman (2002)
Rossel et al (2008)
Steiner & Ryder (2011)
Weinstock et al (2005)

SDZG Library Links