It's estimated that there are at least 196 "uncontacted" Indigenous groups worldwide , living mainly in 10 countries in South America, Asia and the Pacific, including Brazil, Indonesia and India. There aren't strict definitions of what makes a group "uncontacted." The United Nations even notes that the description of such groups can vary from "free, uncontacted, hidden or invisible peoples, peoples in voluntary isolation, etc." "Certainly there is a spectrum between permanent contact, initial contact, sporadic contact and none at all," he told Live Science. It's not uncommon for there to be "little recognition or documentation of an uncontacted group, in fact there are likely many uncontacted groups with no documentation at all," Russell said.