On the sacred walls and inside the dark passageways of ancient ruins in Guatemala, archaeologists are making discoveries that open expanded vistas of the vibrant Maya civilization in its formative period, a time reaching back more than 1,000 years before its celebrated Classic epoch.

The intriguing finds, including art masterpieces and the earliest known Maya writing, are overturning old ideas of the Preclassic period. It was not a kind of dark age, as once thought, of a culture that emerged and bloomed in Classic times, at places like the spectacular royal ruin at Palenque beginning about A.D. 250 and extending to its mysterious collapse around 900.

At the derelict ceremonial center of pyramids and wide plazas, a site in remote northeastern Guatemala known as San Bartolo, archaeologists have uncovered the unexpected remains of murals in vivid colors depicting the Maya mythology of creation and kingship. The murals date to 100 B.C., and nearby, a column of hieroglyphs, a century or two older, attests to an already well-developed writing system.

News of the discoveries, announced in the last six months by an American-Guatemalan team led by William A. Saturno of the University of New Hampshire, is reverberating through the small community of Mayanists.

They see these and other recent finds as strong evidence for the early origin and remarkable continuity of the culture』s concepts of cosmology and possibly governance over more than a Preclassic millennium.

Coming away from a visit to San Bartolo, Michael D. Coe, a retired Yale Mayanist who was not involved in the work, called the murals 「one of the greatest Maya discoveries of all time.」

Stephen Houston, of Brown University, said,」 We are entering a golden age of Pre classic study,」 adding that the discipline of Maya research 「will be marked by a time before the discovery of these paintings in the jungle of Guatemala, and a time thereafter.」 Other experts have already focused new research on Preclassic ruins, some dating at least to 900 B.C., and are reinterpreting finds in light of the San Bartolo evidence.

In her book 「Ritual and Power in Stone,」 to be published in December, Julia Guernsey, a specialist in art history and Maya iconography at the University of Texas, reviews many examples of stucco facades, painted murals and carved monuments that illustrate Preclassic development of the imagery of enduring Maya concepts of creation, the spirit world and the metaphorical expression of power and authority of rulers.

New attention, Dr. Guernsey said, is centered on the common monumental motif in the Classic period that has now been increasingly recognized as early as the middle Preclassic era, 900 to 300 B.C. It is known as the quatrefoil. The design is something like a four-leaf clover and is found in the arrangement of stones or carved in stone or crated with packed earth and painted clay at a ceremonial site, as at La Blanca on the Pacific coastal plain in Guatemala. La Blanca, occupied from 900 B.C. to 600 B.C., is being excavated by Michael W. Love of California State University-Northridge, with Dr. Guernsey as the project iconographer.

Other Preclassic examples are being examined at Izapa, across the Mexican border from La Blanca, where quatrefoils and monuments date to between 300 B.C. and 50 B.C. An Izapa throne is framed in a quatrefoil. Similar imagery has been uncovered in Mexico at Chalcatzingo, dating from as early as 700 B.C.

Archaeologists think the quatrefoil, often in association with water channels and basins, may have been part of the iconography in ceremonies to the rain god and fertility. In other cases, it is formed around a cave entrance, perhaps symbolic of creation and the supernatural.

One new puzzle yet to be solved is the Preclassic Maya script found at San Bartolo. The column of 10 glyphs, painted in black on white plaster, is definitely Maya writing from 300 B.C. to 200 B.C., experts say, but so far it is unreadable.

Dr. Saturno and colleagues reported that the writing sample 「implies that a developed Maya writing system was in use centuries earlier than previously thought, approximating a time when we see the earliest scripts elsewhere in Mesoa