Researchers in Chile say they discovered a human footprint they believe is the oldest ever found in the Americas.Scientists involved in the fossil discovery saidthe footprint dates back at least 15,600 years. Their results are reported in a study published in the scientific journal PLOS One.The footprint was discovered in 2011 at the Pilauco excavation site in the city of Osorno. A student from Chile's Austral University found the footprint. Scientists worked for years to confirm whether the print could have come from a human species.Mario Pino is a professor and geologist at Austral University's Institute of Earth Sciences. He helped examine the fossil. He said carbon dating methods were used to link the footprintto the same time period as plant material found in the area.Pino said his team used the print to estimate the general size, shape and structure of the human foot. Researchers believe it belonged to a barefoot man who weighed about 70 kilograms.Karen Moreno is also with Austral Universityand a lead researcher on the project. She said the print showed evidence of clearly formed toes and a ball at the back of the foot. This would be "consistent with what would happen to (a human) who tries to walk in the mud," Moreno said.Pino said the man likely belonged to a species called Hominipes modernus, which is related to Homo sapiens. Homo sapiens is the species of human that exists today.Moreno said the latest find provides some of the oldest evidence of humans in the Americas. "Little by little in South America, we're starting to find sites with evidence of human presence," she said. "But this is this oldest in the Americas."The study states that the same area in Chile has also produced fossils providing information on other animals, including early elephants and an ancestor of American horses. The digging teams have also found evidence of invertebrates, as well as different forms of ancient plant life and wood material.Moreno said the researchers also found stone artifacts within the same layers of soil as the footprint. This, she believes, could provide more evidence to support a theorythat human settlements existed in the Americas well before a group known as the "Clovis" hunters.The Clovis group was a prehistoric culture that many scientists believed were the first to arrivein North America -- about 13,000 years ago.But some scientists have suggested that artifacts discovered in recent years suggest other humans might have arrived in the Americas about 1,500 years earlier.