Sus species, like all suids, are native to the Eurasian and African continents, ranging from Europe to the Pacific islands.

[2] Pigs live in complex social groups and are considered one of the more intelligent mammals, as reflected in their ability to learn.

[7] The Online Etymology Dictionary provides anecdotal evidence as well as linguistic, saying that the term derives probably from Old English *picg, found in compounds, ultimate origin unknown.

Synonyms grunter, oinker are from sailors' and fishermen's euphemistic avoidance of uttering the word pig at sea, a superstition perhaps based on the fate of the Gadarene swine, who drowned.

[10] A typical pig has a large head with a long snout that is strengthened by a special prenasal bone and by a disk of cartilage at the tip.

An estimated 50% of piglet fatalities are due to the mother attacking, or unintentionally crushing, the newborn pre-weaned animals.

[14] With around 1 billion individuals alive at any time, the domestic pig is one of the most numerous large mammals on the planet.

Its many subspecies are native to all but the harshest climates of continental Eurasia and its islands and Africa as well, from Ireland and India to Japan and north to Siberia.

Traditionally, pigs were raised on dairy farms and fed any excess milk and the whey left over from cheese and butter making.

In May 1946, in response to a shortage of pig bristles for paintbrushes to paint houses in the post-World War II construction boom, the Royal Australian Air Force (RAAF) flew in 28 short tons of pig bristles from China, their only commercially available source at the time.

[26] It is now thought that pigs were attracted to human settlements for the food scraps, and that the process of domestication began as a commensal relationship.

[31] In some parts of China pigs were kept in pens from early times, separating them from wild populations and allowing farmers to create breeds that were fatter and bred more quickly.

Though ecologically logical as well as economical, pig toilets are waning in popularity as use of septic tanks and/or sewerage systems is increasing in rural areas.

Hernando de Soto and other early Spanish explorers brought pigs to southeastern North America from Europe.

As in Medieval Europe, pigs are valued on certain oceanic islands for their self-sufficiency, which allows them to be turned loose, although the practice does have drawbacks (see environmental impact).

A model that fitted the data included admixture with a now extinct ghost population of wild pigs during the Pleistocene.

[41][42] The pig has been celebrated throughout Europe since ancient times in its carnivals, the name coming from the Italian carne levare, the lifting of meat.

[43] Pigs have been brought into literature for varying reasons, ranging from the pleasures of eating, as in Charles Lamb's A Dissertation upon Roast Pig, to William Golding's Lord of the Flies (with the fat character "Piggy"), where the rotting boar's head on a stick represents Beelzebub, "lord of the flies" being the direct translation of the Hebrew בעל זבוב, and George Orwell's allegorical novel Animal Farm, where the central characters, representing Soviet leaders, are all pigs.

Accidental or deliberate releases of pigs into countries or environments where they are an alien species have caused extensive environmental change.

Their omnivorous diet, aggressive behaviour, and their feeding method of rooting in the ground all combine to severely alter ecosystems unused to pigs.

This results in habitat alteration, a change in plant succession and composition and a decrease in native fauna dependent on the original habitat.Because of their biological similarities, pigs can harbour a range of parasites and diseases that can be transmitted to humans.