Razorbacks, also referre to as an Old World swine, Eurasian wild boar, or Russian wild boar, are feral pigs that were brought to North America by the explorer Hernando de Soto during the mid-1550s. The animal evolved due to a system of farming known as free roam or free range farming, where domesticated animals were allowed to roam freely and are identified by a brand, or burned marking, on their hides. Though pigs were successfully farmed this way, many were lost. These lost pigs eventually made up the first razorback populations. This type of farming eventually declined because of space limitations and because of the desire to obtain hard fat, which can only be harvested from pigs on strict diets.