New research has revealed that a wooden tablet from Rapa Nui—also known as Easter Island—inscribed with mysterious glyphs was likely created before the Europeans’ arrival, meaning the script may be one of history’s rare independently invented writing systems.

Rapa Nui is best known for its moai, the large-scale stone statues that mystified the Europeans who arrived in the 18th century. But it wasn’t until the 19th century that Europeans took note of another significant invention: a system of writing known as “rongorongo” script. In 1864, the missionary Eugene Eyraud described the island’s many “wooden tablets or staffs covered with sorts of hieroglyphic characters.”

The rongorongo script is shrouded in mystery. Only some two dozen artifacts featuring it survive today, and they’re held by institutions all over the world (including the Smithsonian’s National Museum of Natural History).