Verily unmolested by the unknown

Some years ago, in The End of Science , John Horgan announced that scholars would soon encounter the limits of knowledge. Certain questions, such as those relating to the first life on earth, would find no definitive answers. The inquisitive, lacking any certainty in our ironic age, would need to live with incomplete truths, in the company of fellow latecomers who had missed the age of Darwin and Einstein. What Horgan failed to address was the nature of these limits. Did they exist simply because we were all in mop-up mode, filling in minor details of knowledge within the framework of Big Established Truths? Or were there limits on evidence that, if remedied by future discoveries, would allow unexpected breakthroughs? Horgan, a journalist with sharp axes to grind, favoured the first perspective. But some of us remain less certain that the world is so dully predictable or our horizons so finite.

A good place to evaluate Horgan's cramped world view is in the matter of decipherment, the reading of ancient writing systems that have yet to meet their Jean-Francois Champollion or Michael Ventris. Decipherment is not for the faint of heart. It attracts those who believe in progress and the possibility of future knowledge. Such explorers are not "Horgan's Heroes", the scholars Horgan interviewed to support his theory of epistemological decrepitude. But decipherment can also attract those with little self-restraint. The stakes are high, and intellectual glory accrues to those who claim the prize of being the first to read the texts left by long-vanished civilisations.

The key is at once to think small and big: small, by crafting method and achieving incremental gains; big, by aiming for a comprehensive vision of how ancient script recorded sound and meaning. Unfortunately, for every Ventris, there are people such as, say, Steven Roger Fischer. His autobiographical Glyphbreaker makes the reader wince. In what is presumably a self-authored book jacket, Fischer modestly claims "a unique place in the pantheon of glyphbreakers" for having deciphered two scripts: those of the Phaistos disc, unearthed in Crete, and the wholly distinct Rongorongo tablets, from Easter Island. Unpersuasive readings have a high risibility factor, thus Fischer on the Phaistos disc: "My night, my great: Ye loose me now. These afflictions so terrible and so great, verily so molestful."

Zapotec writing is among the last undeciphered scripts from the ancient world. It was developed and used by people in what is now the Mexican state of Oaxaca from c. 500BC - the beginning dates are controversial - to about AD1000. Thus it was apparently the first writing system of the New World. The great Mexican city of Teotihuac n, one of the largest urban zones on earth at the time, attests to its use at an ethnic enclave occupied by Zapotec. Zapotec Hieroglyphic Writing by Javier Urcid Serrano brings the problem of Zapotec decipherment back to our attention in a work of staggering energy and ambition. Almost two decades of research have gone into this book, which builds on Urcid's doctoral thesis at Yale University. The title self-consciously evokes Sir Eric Thompson's Maya Hieroglyphic Writing (1950) but omits Thompson's subtitle, "An introduction". This is appropriate. Urcid does not so much introduce the script as include virtually all that is known about this writing system. His work is the basic, perhaps definitive, source on this poorly understood system. Nonetheless, it is for specialists, not the casually interested.

The question is, to what extent is Urcid a Ventris or a Fischer? And does Zapotec decipherment prompt optimism or dejection? The evidence strongly suggests that Urcid fits squarely in an intermediate category of sober and clear-eyed tenacity in the face of what may be a nearly impenetrable writing system. Previous scholars, such as Joyce Marcus of the University of Michigan, have treated Zapotec writing as though it consisted of loosely linked icons, to be read willy-nilly, as filtered through a banal historicism that reduces Zapotec inscriptions to propagandistic manoeuvres by kings. Urcid devotes more than half his book to resolving remaining controversies about Zapotec calendrical dates in the texts, a point of some urgency because it assists with chronology and represents a real opening to something that can be explained.

For this reason, the indeterminate nature of the results is disheartening, as is Urcid's attempt to establish the original provenance - the "programs" - of carved monoliths depending on whether carvings pertain to wide ("Program A") or narrow surfaces ("Program B"). The operative word is Urcid's own descriptive, "hypothetical", to the extent that the exercise may not have been worthwhile. A chain of assumptions is only as strong as its weakest link.

Urcid's conclusions are telling. A decipherment relates writing to language and makes the opaque transparent. A connection between the Zapotec language and this script is likely, given the concurrence of hieroglyphic distribution and the region where this tonal language is used. But absolute proof is lacking, and only tentative parallels are established between grammatical elements of the Zapotec language and configurations of hieroglyphs. The problem appears to be that most of the signs may well be word signs, without syllabic or phonetic clues to clarify sound and meaning. A considerable number of hieroglyphs appear only once, as on the brilliantly finished Lápida de Bazan, or they exist in insufficient quantity to evaluate their behaviour. Unlike Maya glyphs, which have a "biscript" in the form of Bishop Diego de Landa's tabulation of Spanish-glyphic equivalents, no such evidence occurs for the non-calendrical word-signs in Zapotec.

Urcid suggests a future for Zapotec decipherment, but not necessarily a bright one. By gathering more texts and understanding greater details of the Zapotec language, "the phonetic aspects of the script might be deciphered" (my emphasis). In Zapotec Hieroglyphic Writing , Urcid has presented a work of dignity and resolve, some reserve and, indirectly, a riposte to Horgan. A distant horizon of discovery awaits us, but our present tools cannot take us there. Urcid is the one person to make that journey and prepare another edition of this book 20 years from now.

Stephen Houston is professor of anthropology, Brigham Young University, Utah, US. He specialises in Maya art, writing and archaeology.