There are nine living species of pig and hogs. The domesticated pig is believed to be descended from the European wild boar. From its Euarsian origins, the pig has been introduced all over the world by humans. Christopher Columbus introduced the first pigs to the New World. Pigs are not found in regions such as the Middle East, where Judaism and Islam are the predominant religions, because they are considered to be unclean animals in these religions.
Pigs have a keen sense of smell and excellent hearing, but poor vision.
Their highly mobile snouts enable them to root in the ground for food. Their reputation for being dirty presumably comes from the fact that they wallow in mud. They do so in order to protect themselves from the sun and heat and from parasitic insects. Despite this reputations, pigs are very clean animals. That, combined with their intelligence, adaptability, and trainability, have led to their increasing popularity as household pets.