When archaeologists on a dig in southern Portugal last year flipped over a heavy chunk of slate and saw writing not used for more than 2,500 years, they were elated.
The enigmatic pattern of inscribed symbols curled symmetrically around the upper part of the rough-edged, yellowish stone tablet and coiled into the middle in a decorative style typical of an extinct Iberian language called Southwest Script.
"We didn't break into applause, but almost," says Amilcar Guerra, a University of Lisbon lecturer overseeing the excavation. "It's an extraordinary thing."
For more than two centuries, scientists have tried to decipher Southwest Script, believed to be the peninsula's oldest written tongue and, along with Etruscan from modern-day Italy, one of Europe's first.
The stone tablet features 86 characters and provides the longest-running text of the Iron Age language ever found.
About 90 slate tablets bearing the ancient inscriptions have been recovered, most of them incomplete. Almost all were scattered across southern Portugal, though a handful turned up in the neighboring Spanish region of Andalucia.
Some of the letters look like squiggles. Others are like crossed sticks. One resembles the number four and another recalls a bow-tie. They were carefully scored into the slate. The text is always a running script, with unseparated words which usually read from right to left.
The first attempts to interpret this writing date from the 18th century. It aroused the curiosity of a bishop whose diocese encompassed this region where the earth keeps coughing up new fragments.
Almodovar, a rural town of some 3,500 people amid a gentle landscape of meadows punctuated by whitewashed towns, sits at the heart of the Southwest Script region. It created a museum two years ago where 20 of the engraved tablets are on show.
Though the evidence is gradually building as new tablets are found, researchers are handicapped because they are peering deep into a period of history about which they know little, says professor Pierre Swiggers, a Southwest Script specialist at the University of Leuven, Belgium.
Scientists have few original documents and hardly any parallel texts from the same time and place in readable languages.
"We hardly know anything about (the people's) daily habits or religious beliefs," he says.
Southwest Script is one of just a handful of ancient languages about which little is known, according to Swiggers. The obscurity has provided fertile ground for competing theories about who wrote these words.
It is generally agreed the texts date from between 2,500 and 2,800 years ago. Most experts have concluded they were authored by a people called Tartessians, a tribe of Mediterranean traders who mined for metal in these parts — one of Europe's largest copper mines is nearby — but disappeared after a few centuries.
Some scientists have proposed that the composers were other pre-Roman tribes, such as the Conii or Cynetes, or maybe even Celts who roamed this far south.
Another translation difficulty is that the writing is not standardized. It seems certain that it was adapted from the Phoenician and Greek alphabets because it copied some of their written conventions. However, it also tweaked some of those rules and invented new ones.
Experts have identified characters that represent 15 syllables, seven consonants and five vowels. But eight characters, including a kind of vertical three-pronged fork, have confounded attempts at comprehension.
There's also the problem of figuring out what messages the slate tablets are intended to convey. Even when they can read portions of text, scientists don't really understand what it is saying — like a child mouthing the words of a Shakespeare play.
"We have a lot of doubts," says Guerra, who has written scholarly articles about Southwest Script. "We can read characters and see the phonetics in action ... but when we try to understand what they actually mean we have a lot of problems."
There are clues, however.
The symmetrical, twisting text gives the impression of a decorative flourish. Some stones also feature crudely rendered figures, such as a warrior carrying what appear to be spears. The lower part of the rectangular stones is left blank as if intended to be stuck in the ground.
That has led experts to a supposition: The tablets were gravestones for elite members of local Iron Age society. Repeated sequences of words perhaps mean "Here lies..." or "Son of...," Guerra explains. Since most people probably couldn't read, the ornamental elements lent distinction.
These are educated guesses, says Guerra, as he surveys the hilltop dig by a small river where the big stone was found last year. His team here has excavated through centuries of occupation: Islamic (Almodovar is a corruption of the Arabic word al-mudura, meaning encirclement or enclosure), Roman and pre-Roman. Nowadays, it is within view of a wind farm's turbines.
Last year's find has helped, but it wasn't the breakthrough scientists had hoped for, Guerra says. If all the Southwest Script found so far were transcribed onto paper, it would still barely fill a single sheet.
Without an equivalent of the Rosetta stone, which helped unlock the secrets of hieroglyphic writing, efforts to reconstruct the ancient language are doomed to slow progress.
"We have to be patient — and hopeful," Guerra says.