The earliest documented reference to rongorongo was made by a French missionary, Eugene Eyraud, who wrote in 1864 that he thought "the primitive script a custom which [the islanders] preserve without searching for the meaning."

The battered rongorongo tablets in the island's only museum, the Sebastian Englert Museum, certainly look ancient. (The museum is named after a Capuchin priest born in 1888, who was, for 35 years before his death in 1969, the parish priest of Rapa Nui, and who made a complete survey of the ahu).

But despite the tablet's prehistoric appearance, modern scholars are now almost unanimous in dating the origins of the script to less than a century before Eyraud's description.

More specifically, they link the birth of rongorongo directly to the visit, in 1770, of a Spanish delegation to formalize the annexation of Easter Island.

On that occasion, the island's chiefs and priests were presented with a document of annexation, and asked to inscribe their sign to show their consent. The marks they made are largely vague, but a few drew vulva, one of the most commonly found symbolic markings made on the island's inscribed stones, and one sketched a bird, resembling those found in petroglyphs.

This first experience of the written word, scholars now believe, spurred the Rapa Nui to create a written language of their own.

Rongorongo's flowering was short lived, however. By the time the first anthropologists -- Bishop Jaussen of Tahiti in the 1870s and '80s, and William Thomson in 1886 -- began to inquire into the script's meaning, there were no reliable readers of rongorongo left.

Indeed, an attempt made in 1874 to have an islander read one text produced three different versions of it on three successive Sundays.

Then in 1995, linguist Steven Fischer, decoder of the Phaistos Disk (a clay, text-inscribed tablet found at a cult site in Crete in 1908, and dating from the 17th century B.C.) announced that he had cracked the structure of rongorongo. Fischer noticed a tripartite pattern: Symbols were grouped in threes, the first symbol possessing a phallus-like appendage, and the third symbol sometimes repeating the first symbol, but never the second.

Fischer drew comparisons with surviving oral texts written down by early visiting scholars, that were essentially chanted genealogical tables of creation, recording the couplings and offspring of animals, birds, demons and elements. He then declared that rongorongo inscriptions on the so-called Santiago Staff, the largest surviving text, constitute a Rapa Nui Genesis.

Not all scholars accept Fischer's interpretation, but with the 25 surviving texts 25 containing little more than 14,000 characters, it is unlikely that rongorongo will ever fully yield up its secrets.

Nonetheleless, John Flenley and Paul Bahn -- authors of 2003's "The Enigmas of Easter Island" -- describe the script as a "crowing glory" of this unique culture, "one of the most highly evolved Neolithic societies in human history."