Little Foot is one of the world’s most complete ancient human-like fossils. It was found in South Africa’s Sterkfontein cave. The fossil’s name comes from the foot bones first discovered in 1994. It took over 20 years to carefully dig out the full skeleton. For years, scientists thought Little Foot belonged to the species Australopithecus prometheus or Australopithecus africanus. But a new study by Australian scientists in the American Journal of Biological Anthropology finds differences in Little Foot’s bones. Dr Jesse Martin from La Trobe University, who led the study, said, "We think it is a formerly unknown, unsampled species of human ancestor." He added, "It doesn’t look like Australopithecus prometheus … but it also doesn’t look like all of the africanus to come out of Sterkfontein." Martin believes this fossil might be part of a whole new branch of the human family tree. The study found key differences in the back of Little Foot’s skull, especially in the nuchal plane, a part that usually changes very little over evolution. Martin said, "If you find differences between things in the base of the cranium … those differences are more likely to represent different species." The authors did not officially rename Little Foot. They suggested the original excavation team, led by Prof Ronald Clarke, who has long believed in multiple species at Sterkfontein, should do that. There is also debate on Little Foot’s age. Some date it at 3.67 million years, others say no older than 2.8 million. Prof Clarke has been contacted for his comments.