A pig is any of the animals in the genus Sus, within the even-toed ungulate family Suidae. Pigs include domestic pigs (Sus domesticus) and their ancestor, the common Eurasian wild boar (Sus scrofa), along with other species. Pigs, like all suids, are native to the Eurasian and African continents, ranging from Europe to the Pacific islands. Suids other than the pig are the babirusa of Indonesia, the pygmy hog of South Asia, the warthog of Africa, and other pig genera from Africa. The suids are a sister clade to peccaries.
With around 1 billion individuals alive at any time, the domestic pig is among the most populous large mammals in the world. Pigs are omnivores and can consume a wide range of food. Pigs are biologically similar to humans and are thus frequently used for human medical research.
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. Originally "young pig" (the word for adults was swine). Apparently related to Low German bigge, Dutch big ("but the phonology is difficult" -- OED). ... Another Old English word for "pig" was fearh, related to furh "furrow," from PIE *perk- "dig, furrow" (source also of Latin porc-us "pig," see pork). "This reflects a widespread IE tendency to name animals from typical attributes or activities" [Roger Lass]. 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.
The Online Etymology Dictionary also traces the evolution of sow, the term for a female pig, through various historical languages:
Old English sugu, su "female of the swine," from Proto-Germanic *su- (cognates: Old Saxon, Old High German su, German Sau, Dutch zeug, Old Norse syr), from PIE root *su- (cognates: Sanskrit sukarah "wild boar, swine;" Avestan hu "wild boar;" Greek hys "swine;" Latin sus "swine", suinus "pertaining to swine"; Old Church Slavonic svinija "swine;" Lettish sivens "young pig;" Welsh hucc, Irish suig "swine; Old Irish socc "snout, plowshare"), possibly imitative of pig noise; note that Sanskrit sukharah means "maker of (the sound) su".
An adjectival form is porcine. Another adjectival form (technically for the subfamily rather than genus name) is suine (comparable to bovine, canine, etc.); for the family, it is suid (as with bovid, canid).
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. The snout is used to dig into the soil to find food and is a very acute sense organ. Each foot has four hoofed toes, with the two larger central toes bearing most of the weight, and the outer two also being used in soft ground.
The dental formula of adult pigs is 126.96.36.199, giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male, the canine teeth form tusks, which grow continuously and are sharpened by constantly being ground against each other.
Occasionally, captive mother pigs may savage their own piglets, often if they become severely stressed. Some attacks on newborn piglets are non-fatal. Others may kill the piglets and sometimes, the mother may eat them. An estimated 50% of piglet fatalities are due to the mother attacking, or unintentionally crushing, the newborn pre-weaned animals.
The ancestor of the domestic pig is the wild boar, which is one of the most numerous and widespread large mammals. 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.
Long isolated from other pigs on the many islands of Indonesia, Malaysia, and the Philippines, pigs have evolved into many different species, including wild boar, bearded pigs, and warty pigs. Humans have introduced pigs into Australia, North and South America, and numerous islands, either accidentally as escaped domestic pigs which have gone feral, or as wild boar.
The wild boar (Sus scrofa) can take advantage of any forage resources. Therefore, they can live in virtually any productive habitat that can provide enough water to sustain large mammals such as pigs. If there is increased foraging of wild boars in certain areas, they can cause a nutritional shortage which can cause the pig population to decrease. If the nutritional state returns to normal, the pig population will most likely rise due to the pigs' naturally increased reproduction rate.
Pigs are omnivores, which means that they consume both plants and animals. In the wild, they are foraging animals, primarily eating leaves, roots, fruits, and flowers, in addition to some insects and fish. As livestock, pigs are fed mostly corn and soybean meal with a mixture of vitamins and minerals added. Traditionally, they were raised on dairy farms and called "mortgage lifters", due to their ability to use the excess milk and whey from cheese and butter making combined with pasture. Older pigs will consume three to five gallons of water per day. When kept as pets, the optimal healthy diet consists mainly of a balanced diet of raw vegetables, although some may give their pigs conventional mini pig pellet feed.
Most pigs today are domesticated pigs raised for meat (known as pork). Miniature breeds are commonly kept as pets. Because of their foraging abilities and excellent sense of smell, people in many European countries use them to find truffles. Both wild and feral pigs are commonly hunted.
Apart from meat, pig skin is turned into leather, and their hairs are used to make brushes. The relatively short, stiff, coarse pig hairs are called bristles, and were once so commonly used in paintbrushes that in 1946 the Australian Government launched Operation Pig Bristle. 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.
Use in human healthcare
Human skin is very similar to pig skin, therefore many preclinical studies employ pig skin. In addition to providing use in biomedical research and for drug testing, genetic advances in human healthcare have provided a pathway for domestic pigs to become xenotransplantation candidates for humans.
- Sus ahoenobarbus Huet, 1888 – Palawan bearded pig
- Sus barbatus Müller, 1838 - Bornean bearded pig
- Sus cebifrons Heude, 1888 – Visayan warty pig
- Sus celebensis Müller & Schlegel, 1843 – Celebes warty pig or Sulawesi warty pig
- Sus domesticus Erxleben, 1777 – Domestic pig (sometimes considered subspecies of S. scrofa)
- Sus oliveri Groves, 1997 – Oliver's warty pig or Mindoro warty pig
- Sus philippensis Nehring, 1886 – Philippine warty pig
- Sus scrofa Linnaeus, 1758 – Wild boar
- Sus verrucosus Boie, 1832 – Javan warty pig
- † Han, 1987 – Early Pleistocene of China
- † Han et al., 1975 – Early Pleistocene of China
- † – Pleistocene of the Siwalik region, India
- † Qi et al., 1999 – Pleistocene of China
- † Falconer and Cautley 1847 – Pliocene of India
- † Zhao, 1980 – Early Pleistocene of China
- † Han, 1987 – Early Pleistocene of China
- † Zdansky, 1928 – Pleistocene of China
- † Koenigswald, 1933 – Middle Pleistocene of China
- † Han, 1987 – Early Pleistocene of China
- † Xue, 1981
- †Sus strozzi Forsyth Major, 1881 - Pliocene and Early Pleistocene of Europe
- † Han et al., 1975 – Early Pleistocene of China
Pigs have been domesticated since ancient times in the Old World. Pigs were domesticated on each end of Eurasia, and possibly several times. 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. Archaeological evidence suggests that pigs were being managed in the wild in a way similar to the way they are managed by some modern New Guineans from wild boar as early as 13,000–12,700 BP in the Near East in the Tigris Basin, Çayönü, Cafer Höyük, Nevalı Çori. Remains of pigs have been dated to earlier than 11,400 BP in Cyprus that must have been introduced from the mainland which suggests domestication in the adjacent mainland by then.
Pigs were also domesticated in China, potentially more than once. 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. Early Modern Europeans brought these breeds back home and crossed them with their own pigs, which was the origins of most modern pig breeds.
In India, pigs have been domesticated for a long time mostly in Goa and some rural areas for pig toilets. This practice also occurred in China. 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).
The domestic pig (Sus domesticus) is usually given the scientific name Sus scrofa domesticus, although some taxonomists, including the American Society of Mammalogists, call it S. domesticus, reserving S. scrofa for the wild boar. It was domesticated approximately 5,000 to 7,000 years ago. The upper canines form sharp distinctive tusks that curve outward and upward. Compared to other artiodactyles, their head is relatively long, pointed, and free of warts. Their head and body length ranges from 0.9 to 1.8 m (35 to 71 in) and they can weigh between 50 and 350 kg (110 and 770 lb).
In November 2012, scientists managed to sequence the genome of the domestic pig. The similarities between the pig and human genomes mean that the new data may have wide applications in the study and treatment of human genetic diseases.
In August 2015, a study looked at over 100 pig genome sequences to ascertain their process of domestication. The process of domestication was assumed to have been initiated by humans, involved few individuals and relied on reproductive isolation between wild and domestic forms. The study found that the assumption of reproductive isolation with population bottlenecks was not supported. The study indicated that pigs were domesticated separately in Western Asia and China, with Western Asian pigs introduced into Europe where they crossed with wild boar. A model that fitted the data included admixture with a now extinct ghost population of wild pigs during the Pleistocene. The study also found that despite back-crossing with wild pigs, the genomes of domestic pigs have strong signatures of selection at DNA loci that affect behavior and morphology. The study concluded that human selection for domestic traits likely counteracted the homogenizing effect of gene flow from wild boars and created domestication islands in the genome. The same process may also apply to other domesticated animals. 
Pigs have been important in culture across the world since neolithic times. They appear in art, literature, and religion. In Asia the wild boar is one of 12 animal images comprising the Chinese zodiac, while in Europe the boar represents a standard charge in heraldry. In Islam and Judaism pigs and those who handle them are viewed negatively, and the consumption of pork is forbidden. Pigs are alluded to in animal epithets and proverbs. 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.
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.
Domestic pigs that have escaped from urban areas or were allowed to forage in the wild, and in some cases wild boars which were introduced as prey for hunting, have given rise to large populations of feral pigs in North and South America, Australia, New Zealand, Hawaii, and other areas where pigs are not native. 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. Pigs will even eat small animals and destroy nests of ground nesting birds. The Invasive Species Specialist Group lists feral pigs on the list of the world's 100 worst invasive species and says:
Feral pigs like other introduced mammals are major drivers of extinction and ecosystem change. They have been introduced into many parts of the world, and will damage crops and home gardens as well as potentially spreading disease. They uproot large areas of land, eliminating native vegetation and spreading weeds. 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. Examples of such zoonoses include trichinosis, Taenia solium, cysticercosis, and brucellosis. Pigs also host large concentrations of parasitic ascarid worms in their digestive tracts.
Some strains of influenza are endemic in pigs, the most significant of which are H1N1, H1N2, and H3N2, the former of which has caused several outbreaks among humans, including the Spanish flu, 1977 Russian flu pandemic, and the 2009 swine flu pandemic. Pigs also can acquire human influenza.
- "Piglet". Merriam-Webster. 31 August 2012. Retrieved 15 September 2013.
- Angier, Natalie (9 November 2009). "Pigs Prove to Be Smart, if Not Vain". The New York Times. ISSN 0362-4331.
- "PSD Online". United States Department of Agriculture. Archived from the original on 2010-10-18. Retrieved 2008-08-17.
- "Swine Summary Selected Countries". United States Department of Agriculture Foreign Agricultural Service. 14 October 2011. Archived from the original on 29 March 2012 – via Wayback Machine.
- Kantharidis, Billy (27 June 2014). "Pig And Human Digestive System". Prezi. Retrieved 15 April 2016.
- Grush, Loren (9 May 2014). "Why pigs are so valuable for medical research". Fox News. Retrieved 15 April 2016.
- "Sow". Online Etymology Dictionary. Retrieved 4 December 2015.
- Wickline, Kristin (2014). "Sus scrofa". Animal Diversity Web.
- Kim Lockhart. "American Wild Game / Feral Pigs / Hogs / Pigs / Wild Boar". Gunners Den. Archived from the original on 23 August 2018. Retrieved 3 December 2018.
- Harris, M., Bergeron, R., Li1, Y. and Gonyou, H. (2001). "Savaging of piglets: A puzzle of maternal behaviour" (PDF). Retrieved July 31, 2013.CS1 maint: multiple names: authors list (link)[permanent dead link]
- Lay, Dr. Donald C., Jr. "MANAGEMENT TIPS TO REDUCE PRE-WEANING MORTALITY". North Carolina Pork Conference. Archived from the original on 20 August 2007 – via Wayback Machine.
- Mayer, John J.; Brisbin, I. Lehr, Jr. (2009). "Wild Pigs Biology, Damage, Control Techniques and Management" (PDF). Savannah River National Laboratory, Aiken, South Carolina: Auburn University. Archived from the original (PDF) on 28 March 2014.
- "Diet and Nutrition on Modern Pig Farms". Pork Cares. Archived from the original on 2 October 2017. Retrieved 17 October 2017.
- Hurt, Chris (29 November 2004). "WILL HOGS RECLAIM "MORTGAGE LIFTER" STATUS?". Farmdoc. University of Illinois at Urbana–Champaign. Archived from the original on 12 August 2013. Retrieved 17 June 2013.
- Almond, Glen W. "How Much Water Do Pigs Need?". Raleigh, North Carolina: North Carolina State University.
- "Mini Pig Nutrition". American Mini Pig Association.
- "PIG BRISTLES FOR PAINT BRUSHES". Townsville Daily Bulletin. Queensland: Trove. 29 May 1946. p. 4. Retrieved 15 April 2016.
- Herron, Alan J. (5 December 2009). "Pigs as Dermatologic Models of Human Skin Disease" (PDF). Ivis. American College of Veterinary Pathologists. DVM Center for Comparative Medicine and Department of Pathology Baylor College of Medicine Houston, Texas. Retrieved 27 January 2018.
pig skin has been shown to be the most similar to human skin. Pig skin is structurally similar to human epidermal thickness and dermal-epidermal thickness ratios. Pigs and humans have similar hair follicle and blood vessel patterns in the skin. Biochemically pigs contain dermal collagen and elastic content that is more similar to humans than other laboratory animals. Finally pigs have similar physical and molecular responses to various growth factors.
- Liu, J.; Kim, D.; Brown, L.; Madsen, T.; Bouchard, G.F. "Comparison of Human, Porcine and Rodent Wound Healing With New Miniature Swine Study Data" (PDF). Sinclair Research. Retrieved 27 January 2018.
Pig skin is anatomically, physiologically, biochemically and immunologically similar to human skin, and the skin is ‘fixed skin’ like humans and unlike rodents or rabbits.
- Swindle, M. M.; Makin, A.; Herron, A. J.; Clubb, F. J.; Frazier, K. S. (2012). "Swine as Models in Biomedical Research and Toxicology Testing". Veterinary Pathology. 49 (2): 344–356. doi:10.1177/0300985811402846. PMID 21441112.
- Jeffery, Simon (3 January 2002). "Pig to Human transplants". The Guardian.
- Funk, Stephan M.; Kumar Verma, Sunil; Larson, Greger; Prasad, Kasturi; Singh, Lalji; Narayan, Goutam; Fa, John E. (November 2007). "The pygmy hog is a unique genus: 19th century taxonomists got it right first time round". Molecular Phylogenetics and Evolution. 45 (2): 427–436. doi:10.1016/j.ympev.2007.08.007. PMID 17905601 – via Elsevier ScienceDirect.
- Price, Max; Hongo, Hitomi (2020). "The archaeology of pig domestication in Eurasia". Journal of Archaeological Research. 28 (4): 557–615. doi:10.1007/s10814-019-09142-9. hdl:1721.1/128524. S2CID 214309500.
- Zeder, Melinda (2021). "The Domestication of Animals". Journal of Anthropological Research. 68 (2): 161–190. doi:10.3998/jar.0521004.0068.201. S2CID 85348232.
- Rosenberg, M; Nesbitt, R; Redding, RW; Peasnall, BL (1998). "Hallan Cemi, pig husbandry, and post-Pleistocene adaptations along the Taurus-Zagros Arc (Turkey)"". Paléorient. 24 (1): 25–41. doi:10.3406/paleo.1998.4667 – via Persée.
- Ottoni, C.; Girdland Flink, L.; Evin, A.; Geörg, C.; De Cupere, B.; Van Neer, W.; Bartosiewicz, L.; Linderholm, A.; Barnett, R.; Peters, J.; Decorte, R.; Waelkens, M.; Vanderheyden, N.; Ricaut, F. X.; Çakırlar, C.; Cevik, O.; Hoelzel, A. R.; Mashkour, M.; Mohaseb Karimlu, A. F.; SheikhiSeno, S.; Daujat, J.; Brock, F.; Pinhasi, R.; Hongo, H.; Perez-Enciso, M.; Rasmussen, M.; Frantz, L.; Megens, H. J.; Crooijmans, R.; et al. (22 November 2012). "Pig domestication and human-mediated dispersal in western Eurasia revealed through ancient DNA and geometric morphometrics". Molecular Biology and Evolution (published April 2013). 30 (4): 824–832. doi:10.1093/molbev/mss261. PMC 3603306. PMID 23180578.
- Vigne, JD; Zazzo, A; Saliège, JF; Poplin, F; Guilaine, J; Simmons, A (18 August 2009). "Pre-Neolithic wild boar management and introduction to Cyprus more than 11,400 years ago". Proceedings of the National Academy of Sciences of the United States of America. 106 (38): 16135–16138. Bibcode:2009PNAS..10616135V. doi:10.1073/pnas.0905015106. PMC 2752532. PMID 19706455.CS1 maint: date and year (link)
- Giuffra, E; Kijas, J. M.; Amarger, V; Carlborg, O; Jeon, J. T.; Andersson, L (April 2000). "The origin of the domestic pig: independent domestication and subsequent introgression". Genetics. 154 (4): 1785–91. doi:10.1093/genetics/154.4.1785. PMC 1461048. PMID 10747069 – via National Center for Biotechnology Information.
- Lander, Brian; Schneider, Mindi; Brunson, Katherine (2020). "A history of pigs in China: From curious omnivores to industrial pork". The Journal of Asian Studies. 79 (4): 865 - 889. doi:10.1017/S0021911820000054. S2CID 225700922.
- White, Sam (2011). "From Globalized Pig Breeds to Capitalist Pigs: A Study in Animal Cultures and Evolutionary History". Environmental History. 16 (1): 94-120. doi:10.1093/envhis/emq143.
- Hsu, Christine (14 November 2012). "Scientists Sequence Entire Pig Genome in Breakthrough That Could Combat Human Disease". Medical Daily. IBT Media.
- "Scientists decode the pig genome". Business Standard. Press Trust of India. London. 15 November 2012.CS1 maint: others (link)
- Groenen, Martien A. M.; Archibald, Alan L.; Uenishi, Hirohide; Tuggle, Christopher K.; Takeuchi, Yasuhiro; Rothschild, Max F.; Rogel-Gaillard, Claire; Park, Chankyu; Milan, Denis; Megens, Hendrik-Jan; Li, Shengting; Larkin, Denis M.; Kim, Heebal; Frantz, Laurent A. F.; Caccamo, Mario; Ahn, Hyeonju; Aken, Bronwen L.; Anselmo, Anna; Anthon, Christian; Auvil, Loretta; Badaoui, Bouabid; Beattie, Craig W.; Bendixen, Christian; Berman, Daniel; Blecha, Frank; Blomberg, Jonas; Bolund, Lars; Bosse, Mirte; Botti, Sara; et al. (2012). "Analyses of pig genomes provide insight into porcine demography and evolution". Nature. 491 (7424): 393–8. Bibcode:2012Natur.491..393G. doi:10.1038/nature11622. PMC 3566564. PMID 23151582.
- Frantz, Lauren A F; Schraiber, Joshua G; Madsen, Ole; Megens, Hendrik-Jan; Cagan, Alex; Bosse, Mirte; Paudel, Yogesh; Crooijmans, Richard P M A; Larson, Greger; Groenen, Martien A M (31 August 2015). "Evidence of long-term gene flow and selection during domestication from analyses of Eurasian wild and domestic pig genomes". Nature Genetics. 47 (10): 1141–8. doi:10.1038/ng.3394. PMID 26323058. S2CID 205350534.CS1 maint: date and year (link)
- Pennisi, Elizabeth (31 August 2015). "The taming of the pig took some wild turns". Science Magazine. doi:10.1126/science.aad1692. Archived from the original on 1 September 2015.
- Qur'an 2:173, 5:3, 6:145, and 16:115.
- Leviticus 11:3–8
- Horwitz, Richard P. (2002). Hog Ties: Pigs, Manure, and Mortality in American Culture. University of Minnesota Press. p. 23. ISBN 0816641838.
- "Fine Swine". The Daily Telegraph. 2 February 2001.
- Komins, Benton Jay (2001). "Western Culture and the Ambiguous Legacies of the Pig". Comparative Literature and Culture. Purdue University. 3 (4). doi:10.7771/1481-4374.1137. ISSN 1481-4374.
- Mullan, John (21 August 2010). "Ten of the best pigs in literature". The Guardian.
- Bragg, Melvyn. "Topics - Pigs in literature". BBC Radio 4. Retrieved 1 January 2020.
Animal Farm ... Sir Gawain and the Green Knight ... The Mabinogion ... The Odyssey ... (In Our Time)
- Sillar, Frederick Cameron (1961). The symbolic pig: An anthology of pigs in literature and art. Oliver & Boyd.
- "Species profile: Sus scrofa". Invasive Species Specialist Group. International Union for Conservation of Nature. 2016. Archived from the original on 24 March 2016.
- "Managing disease and welfare in swine". The Pig Site. Archived from the original on 2018-09-03. Retrieved 2009-03-12.
- "What People Who Raise Pigs Need To Know About Influenza (Flu)". Centers for Disease Control and Prevention. 19 August 2014. Retrieved 4 March 2021.