Pigs (or hogs, or swine, or Sus – the Latin name for the species) are omnivorous mammals of Eurasian origin, closely related to hippopotami and generally more known for being tasty than clever – although they are pretty intelligent, often considered on a par with dogs.
The pig is nevertheless considered an unclean animal unfit for human consumption by the dietary laws of judaism and islam – possibly because it’s willing to eat its own excrement if no other ‘food’ is available.
Escaped pigs have escalated into large feral populations in places they didn’t naturally occur, such as America, Australia and New Zealand. Being quite agressive, these feral pigs can cause quite a lot of environmental damage.
Most pigs however are bred for human consumption in large industrial farms. This fascinating map, from the US Department of Agriculture Yearbook 1922, shows exactly where that industrial-scale pig-breeding took place in the early 20th century: large concentrations in Europe, the US and China as opposed to almost none beyond those regions.
To quote from said yearbook: “The centers of densest hog production are the Corn Belts of the US and Hungary, the potato and dairying belt of northern Europe, and China, where hogs are fed largely on waste products and barley (…) In the corn-growing regions of Argentina and southern Brazil the number of hogs is increasing. Hogs are not numerous in tropical countries, because such countries, as a rule, are not densely populated and have available the vegetable oils to supply the needed fats (…) Religion practically excludes hogs from India, Turkey and certain other parts of Asia;also from parts of Africa.”
This map was taken from this page labelled Maps Etc., a repository of many nice maps, even if they’re not all as strange as this one…