The Grolier Codex, a 13th-century Mayan document, regarded among the rarest books in the world, is genuine and likely the most ancient of all surviving manuscripts from America, scientists have found. The document was reportedly unearthed by looters from a cave in Mexico in the 1960s. Researchers reviewed all known research on the manuscript, analysing it without regard to the politics, academic and otherwise, that have enveloped the Grolier. The study is a confirmation that the manuscript, counter to some claims, is quite real, said Stephen Houston, Professor at Brown University in the US. The manuscript was sitting unremarked in a basement of the National Museum in Mexico City, and its history is cloaked in great drama. It was found in a cave in Mexico, and a wealthy Mexican collector, Josue Saenz, had sent it abroad before its eventual return to the Mexican authorities. For years, researchers have argued about the legitimacy of the Grolier Codex. Some asserted that it must have been a forgery, speculating that modern forgers had enough knowledge of Maya writing and materials to create a fake codex at the time the Grolier came to light. The codex was reportedly found in the cave with a cache of six other items, including a small wooden mask and a sacrificial knife with a handle shaped like a clenched fist, researchers said. They add that although all the objects found with the codex have been proven authentic, the fact that looters, rather than archeologists, found the artifacts made specialists in the field reluctant to accept that the document was genuine. "We decided to return and look at it very carefully, to check criticisms one at a time. Now we are issuing a definitive facsimile of the book. There can't be the slightest doubt that the Grolier is genuine," said Houston. Researchers analysed the origins of the manuscript, the nature of its style and iconography, the nature and meaning of its Venus tables, scientific data - including carbon dating - of the manuscript, and the craftsmanship of the codex, from the way the paper was made to the known practices of Maya painters. The Grolier's composition, from its 13th-century amatl paper, to the thin red sketch lines underlying the paintings and the Maya blue pigments used in them, are fully persuasive, researchers said. The Grolier Codex is a fragment, consisting of 10 painted pages decorated with ritual Maya iconography and a calendar that charts the movement of the planet Venus. Mesoamerican peoples, Houston said, linked the perceived cycles of Venus to particular gods and believed that time was associated with deities. The research appears in the journal Maya Archaeology.