Humans likely established permanent settlements on the high-altitude Tibetan plateau at least 7,400 years ago, much before the advent of agriculture 5,200 years ago, says a study.The findings are based on an extensive analysis of human handprints and footprints found in 1998 in fossilised hot spring mud near the village of Chusang on Tibet's central plateau, at an elevation of 14,000 feet above sea level. Analysis of the archaeological site indicated that the prints were made by people at least 7,400 years ago, and possibly as early as 13,000 years ago. The findings, published in the journal Science, challenge the previously held view that permanent human occupation of the Tibetan Plateau began no earlier than development of an agricultural economy between 5,200-3,600 years ago."Although an agropastoral lifeway may have enabled substantial population growth after 5,000 years, it by no means was required for the early, likely permanent, occupation of the high central valleys of the Tibetan Plateau," the researchers wrote.The research sheds new light on human colonisation of high-elevation environments, said one of the researchers, Randy Haas from University of Wyoming in the US.For example, researchers have been puzzled by the striking differences in how Tibetans and Andean highlanders adapted physiologically to the rigors of life at high elevations."High-elevation environments were some of the last places in the world that humans colonised, and so they offer something of a natural laboratory for studying human adaptation," Haas said.