The Evolutionary Relationship Between Horses & Donkeys

Horses and donkeys belong to the same genus--Equus--but are two different species: Equus caballus and Equus assinus. The two are considered cousins, having many similar features. Donkeys are set apart by their long ears, straighter necks, and coarser manes and tails. Donkeys and horses share common ancestors.

  1. Ancestry

    • Dnkeys and horses evolved from Eohippus, the dawn horse, which is thought to have originated in North America. Due to extensive fossil records, scientists have tracked the evolution from Eohippus to Mesohippus to Merychippus to Pliohippus. At Pliohippus, the evolution of the two species, along with zebras, finally separates, approximately 4 million years ago.

    Genetics

    • Donkeys and horses have basically the same genetic information but ordered differently in each species. Horses have 32 pairs of chromosomes while donkeys have just 31. Though still unproven, this is believed to be the reason why resulting offspring of crossing donkeys and horses, known as mules and hinnies, are sterile.

    Domestication

    • Donkeys are believed to have been domesticated prior to horses. Horses are believed to have been domesticated in Persia around 3,000 B.C. Wild donkeys were used by Sumerians in 2,000 B.C. in their conquest of Babylon.