Mule in the context of "Male donkey"

The first evidence of horses in warfare dates from Eurasia between 4000 and 3000 BC. A Sumerian illustration of warfare from 2500 BC depicts some type of equine pulling wagons. By 1600 BC, improved harness and chariot designs made chariot warfare common throughout the Ancient Near East, and the earliest written training manual for war horses was a guide for training chariot horses written about 1350 BC. As formal cavalry tactics replaced the chariot, so did new training methods, and by 360 BC, the Greek cavalry officer Xenophon had written an extensive treatise on horsemanship. The effectiveness of horses in battle was also revolutionized by improvements in technology, such as the invention of the saddle, the stirrup, and the horse collar.

Many different types and sizes of horses were used in war, depending on the form of warfare. The type used varied with whether the horse was being ridden or driven, and whether they were being used for reconnaissance, cavalry charges, raiding, communication, or supply. Throughout history, mules and donkeys, as well as horses played a crucial role in providing support to armies in the field.

A yoke is a wooden beam used between a pair of oxen or other animals to enable them to pull together on a load when working in pairs, as oxen usually do; some yokes are fitted to individual animals. There are several types of yoke, used in different cultures, and for different types of oxen. A pair of oxen may be called a yoke of oxen, and yoke is also a verb, as in "to yoke a pair of oxen". Other animals that may be yoked include horses, mules, donkeys, and water buffalo.

In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, subspecies, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera. Hybrids are not always intermediates between their parents such as in blending inheritance (a now discredited theory in modern genetics by particulate inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are.

Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering times, pollen vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and the structure of the chromosomes. A few animal species and many plant species, however, are the result of hybrid speciation, including important crop plants such as wheat, where the number of chromosomes has been doubled.

Mechanised agriculture or agricultural mechanisation is the use of machinery and equipment, ranging from simple and basic hand tools to more sophisticated, motorised equipment and machinery, to perform agricultural operations. In modern times, powered machinery has replaced many farm task formerly carried out by manual labour or by working animals such as oxen, horses and mules.

The entire history of agriculture contains many examples of the use of tools, such as the hoe and the plough. The ongoing integration of machines since the Industrial Revolution has allowed farming to become much less labour-intensive.

A pack animal, also known as a sumpter animal or beast of burden, is a working animal used to transport goods or materials by carrying them, usually on its back.

Domestic animals of many species are used in this way, among them alpacas, Bactrian camels, donkeys, dromedaries, gayal, goats, horses, llamas, mules, reindeer, water buffaloes and yaks.

A wagon (or waggon) is a heavy four-wheeled vehicle pulled by draft animals or on occasion by humans, used for transporting goods, commodities, agricultural materials, supplies and sometimes people.

Wagons are immediately distinguished from carts (which have two wheels) and from lighter four-wheeled vehicles primarily for carrying people, such as carriages. Common animals which pull wagons are horses, mules, and oxen. One animal or several, often in pairs or teams may pull wagons. However, there are examples of human-propelled wagons, such as mining corfs.

A col in geomorphology is the lowest point on a mountain ridge between two peaks. It may also be called a gap or pass. Particularly rugged and forbidding cols in the terrain are usually referred to as notches. They are generally unsuitable as mountain passes, but are occasionally crossed by mule tracks or climbers' routes. Derived from the French col ("collar, neck") from Latin collum, "neck", the term tends to be associated more with mountain than hill ranges. The distinction with other names for breaks in mountain ridges such as saddle, wind gap or notch is not sharply defined and may vary from place to place. Many double summits are separated by prominent cols.

The height of a summit above its highest col (called the key col) is effectively a measure of a mountain's topographic prominence.

A stirrup is a light frame or ring that holds the foot of a rider, attached to the saddle by a strap, often called a stirrup leather. Stirrups are usually paired and are used to aid in mounting and as a support while using a riding animal (usually a horse or other equine, such as a mule). They greatly increase the rider's ability to stay in the saddle and control the mount, increasing the animal's usefulness to humans in areas such as communication, transportation, and warfare.

In antiquity, the earliest foot supports consisted of riders placing their feet under a girth or using a simple toe loop appearing in India by the 2nd century BC. Later, a single foot support was used as a mounting aid, and paired stirrups appeared after the invention of the treed saddle. The stirrup was invented in the Chinese Jin dynasty during the 4th century, was in common use throughout China by the 5th century, and was spread across Eurasia to Europe through the nomadic peoples of Central Eurasia by the 7th or 8th century.