[5]: 37 A painting in the Tomb of Nebamun at Thebes, dating from approximately 1350 BC, shows a chariot drawn by a pair of animals which have been variously identified as onagers,[6] as mules[5]: 37  or as hinnies.

[12] Mules were used by armies to transport supplies, occasionally as mobile firing platforms for smaller cannons, and to pull heavier field guns with wheels over mountainous trails such as in Afghanistan during the Second Anglo-Afghan War.

The use of mules for farming and for transportation of agricultural products largely gave way to steam-, then diesel-powered, tractors and lorries.

[14]: 2924 [15] In general terms, in both the mule and the hinny, the foreparts and head of the animal are similar to those of the father sire, while the hindparts and tail tend to resemble those of the dam.

[5]: 36  A mule is generally larger than a hinny, with longer ears and a heavier head; the tail is usually covered with long hair like that of its mare mother.

[5]: 37  A mule has the thin limbs, small narrow hooves and short mane of the donkey, while its height, the shape of the neck and body, and the uniformity of its coat and teeth are more similar to those of the horse.

Mules usually display the light points commonly seen in donkeys: pale or mealy areas on the belly and the insides of the thighs, on the muzzle, and around the eyes.

That a hybrid should possess more reason, memory, obstinacy, social affection, powers of muscular endurance, and length of life, than either of its parents, seems to indicate that art has here outdone nature".

[20] The mule inherits from the donkey the traits of intelligence, sure-footedness, toughness, endurance, disposition, and natural cautiousness.

[21]: 5–6, 8  Mules are reputed to exhibit a higher cognitive intelligence than their parent species, but robust scientific evidence to back up these claims is lacking.

Preliminary data exist from at least two evidence-based studies, but they rely on a limited set of specialized cognitive tests and a small number of subjects.

[29] A 1939 article in the Journal of Heredity describes two offspring of a fertile mare mule named "Old Bec," which was owned at the time by Texas A&M University in the late 1920s.

[32] Although it depends on the individual animal, mules trained by the Army of Pakistan are reported to be able to carry up to 72 kg (159 lb) and walk 26 km (16.2 mi) without resting.