In standard SETI scenarios, where humans and extraterrestrials are separated

by trillions of miles, even a signal traveling at the speed of light may take centuries or millennia to reach its recipients. Thus, interstellar communication

may be a one-way transmission of information, rather than a back-and-forth exchange. As we search for analogies to contact at interstellar

distances, archaeology provides some intriguing parallels, given that its practitioners—like successful SETI scientists—are charged with reconstructing

long-lost civilizations from potentially fragmentary evidence. In “A Tale of Two Analogues: Learning at a Distance from the Ancient Greeks and Maya and the Problem of Deciphering Extraterrestrial Radio Transmissions,” anthropologist Ben Finney and historian Jerry Bentley suggest that we might gain clues to decoding extraterrestrial messages by examining past attempts to decode dead languages right here on Earth. As their chapter shows, however, we need to be cautious about which examples to use for our case studies. Given the importance this analogy has played in SETI circles over the years, and the fact that the lessons highlighted in Finney and Bentley’s chapter are also applicable to other translation and decryption challenges addressed elsewhere in this volume, an extended preview of their argument is in order.

Finney and Bentley begin by noting an oft-cited analogy for detecting a message-laden signal from space: the transmission of knowledge from ancient Greece to medieval Europe. During the Dark Ages, European scholars had lost vast numbers of Greek works on philosophy, literature, and science. Fortunately, however, copies of these treatises were preserved by Islamic scholars, particularly in Spain and Sicily. Thus, as Europe entered the Renaissance, Western scholars were able to recover these Greek classics from Islamic centers of learning, either directly from the original manu-scripts or through Arabic translations. And over the succeeding decades and centuries, the “young” European civilization was able to learn from the older Greek civilization, even though the two were separated by long expanses of time.The analogy is an apt one for contact between Earth and the extraterrestrial civilizations being sought by SETI, because if we do detect information-rich signals, they may come from civilizations long since dead. The impact may be even more edifying for us than the influx of classical scholarship was for early modern Europe. This reclaiming of ancient knowledge provided Renaissance Europeans with alternative ways of viewing the world, which led, in turn, to new syntheses of early modern and ancient insights. If someday we detect and decode messages from civilizations beyond Earth, we will have similar opportunities to juxtapose terrestrial and otherworldly views.But, Finney and Bentley warn us, it may not be quite that easy. While the Greek comparison is informative, as with any analogy, it does not tell the whole story. For a more nuanced understanding, they turn to other examples of decoding ancient scripts: Egyptian and Mayan hieroglyphics. Considering here only the first case, the key to decoding ancient Egyptian hieroglyphics was found in a slab now known as the Rosetta Stone, discovered in 1799 by Napoleon’s army during a French military campaign in Egypt. This stone contains the same text written in three languages. Because 19th-century European linguists could read one of these languages, they were eventu-ally able to compare the three inscriptions and thereby decipher the writing system they had previously been unable to crack: Egyptian hieroglyphics.To state what may be obvious, if we receive a message from extrater-restrials, we cannot count on their providing direct translations from one of their native languages to any terrestrial language. And that, say Finney and Bentley, could limit how much we can learn from extraterrestrials. We may be able to understand basic mathematics and astronomy, but once extraterrestrials begin to describe their cultures, interstellar comprehension may suffer considerably. Finney and Bentley point out that those initial successes in decoding scientific parts of an extraterrestrial message might actually stand in the way of understanding more culturally specific parts of the message. As an analogy, they note that when European scholars began decoding ancient Mayan hieroglyphs, their earliest successes were in recognizing the basic numbering system used by the Maya, as well as their calendar systems, which were based on the visible motions of the Moon and Sun. In short, math and science provided the foundation for commu-nication, just as many SETI scientists have predicted will be the case for interstellar communication.

This apparent breakthrough in reading the Mayan glyphs reinforced a Neoplatonic idea that had circulated among European scholars for centuries and which was usually attributed to Plotinus. This Egyptian-born Roman philosopher of the 3rd century followed the Platonic tradition, in which the bedrock of reality is not in the things we can see with our eyes and feel with our hands; instead, ultimate reality consists of underlying Ideas or Forms that serve as blueprints for the material world. Plotinus applied this philosophical concept to Egyptian hieroglyphics, seeing them not as abstract representations of objects but as direct expressions of the ideal essence or divine nature of those objects. They could thus symbolize ideas without the intermediary of merely human languages. Maurice Pope summarizes Plotinus’s view this way: “Each separate sign is in itself a piece of knowledge, a piece of wisdom, a piece of reality, immediately present.”4 Renaissance humanists likewise believed that Egyptian hieroglyphics offered a way to escape the messiness of spoken language by directly representing ideas.As it turns out, Plotinus was wrong, but he was in good company. Right up to the early 19th century, most eminent Egyptologists agreed with him. They dismissed the possibility that hieroglyphs could represent something as mundane as spoken language. But in the 1820s, French linguist Jean-François Champollion used the Rosetta Stone to draw parallels between the as-yet-undeciphered Egyptian hieroglyphics and both well-understood Greek and a form of Egyptian script used widely in business transactions. As a result, Champollion was able to show that hieroglyphics often do represent sounds, much like other languages. Though Plotinus’s dream was broken, so, too, was the mystery of Egyptian hieroglyphics.SETI scientists can learn an important lesson from the history of decod-ing hieroglyphics. Preliminary assumptions about the nature of the message can lead us astray—especially when those assumptions help us to decode parts of the message. While it is true that some Mayan characters refer directly to numbers and months, the vast majority do not. The key then to decoding ancient hieroglyphics, and perhaps also messages from extraterres-trials, is to remain open to new possibilities, even if they seem to contradict initial successes.Literary theorist Richard Saint-Gelais is less optimistic than Finney and Bentley that the linguistic techniques used to decode ancient texts can be successfully applied to interstellar messages. In “Beyond Linear B: The Meta-semiotic Challenge of Communication with Extraterrestrial Intelligence,” Saint-Gelais notes that the SETI scientists who receive a message from extra-terrestrial intelligence will face a twofold task. They must first recognize the signal as a message and must then determine what it means—all without having any prior arrangement with the sender about the acceptable ranges of formats or contents. As a terrestrial analogy of this project, Saint-Gelais outlines the process by which ancient texts have been deciphered. Initially, the linguist needs to determine the constituent components of a language on the basis of a limited sample—its phonemes (or sounds) and words that bear semantic content. This must be done without knowing, for example, how many letters the unknown language contains and whether the variations between similar-looking characters are due to the differences that occur when writing down the same letter twice or to the fact that they represent two different letters.The breakthrough in decoding unknown languages has usually come by finding a bilingual text in which the same passage appears in both the unknown language and a language known to the decipherer, as in the case of the Rosetta Stone. Even when only fragmentary texts are available, a transla-tor can sometimes identify proper names to use as a starting point. But in interstellar communication, we would have no bilingual texts and no proper names recognizable by both civilizations. In those rare instances when ter-restrial linguists have been able to break the code of a lost language without a bilingual text or known proper names, Saint-Gelais argues, they have used methods that would be difficult to apply to understanding interstellar mes-sages. For example, although Michael Ventris used purely formal methods in the 1950s to decipher Linear B from inscriptions on clay tablets found on the island of Crete, his success ultimately derived from his ability to recognize Linear B as a transcription of an ancient form of Greek—and that recognition required his familiarity with the Greek language.Archaeologist and anthropologist Kathryn Denning raises similar concerns about the view often expressed by those most involved in SETI that decoding messages from extraterrestrials will be an easy task. In “Learning to Read: Interstellar Message Decipherment from Archaeological and Anthropological Perspectives,” she urges caution when choosing the models we use to under-stand interstellar communication. Cryptological and other communications approaches share with SETI certain epistemological commitments, but Denning notes that these approaches also carry implicit assumptions that make them unsuitable for interpreting interstellar messages. As an example, Denning points out that Claude Shannon’s information theory has been accepted in SETI circles as a useful tool for understanding communication between species. However, Denning questions its relevance as an analogy—at least as it is often used. She notes that whereas information theory can provide a quantitative measure of the complexity of a communication system, it does not tackle the challenge of determining what the communication means. Likewise, the SETI community’s reliance on cryptological models fails to recognize the false analogy between, on the one hand, breaking a code con-structed by other humans and, on the other hand, understanding a message from an extraterrestrial. In the first, we already know the language, and the challenge is to find a key that will let us derive the original message from the encoded message. In interstellar communication, however, we cannot assume any shared language.Denning, then, has significant reservations about the assertions of SETI scientists who contend that combining sufficient quantities of redundant information with select explanations, such as pictures of objects, will be enough to give extraterrestrials access to human ways of viewing the world. Instead, she maintains that the best linguistic analogies for comprehending alien minds come from cases in which the meaning of communications from other cultures remains opaque even after much study, as with the Rongorongo script or Linear A.Archaeologist Paul Wason agrees with other contributors to this volume that there may be significant, perhaps insurmountable obstacles to interpret-ing the specific meaning of messages from extraterrestrials. Nevertheless, he argues in “Inferring Intelligence: Prehistoric and Extraterrestrial” that archae-ology can make a significant contribution by helping to clarify when a signal is actually intended as a medium of communication. To do so, however, requires a creative combination of different lines of reasoning.Wason observes that archaeologists sometimes use “ethnographic analo-gies,” drawing upon an understanding of cultures to which modern-day anthropologies have access, so they can make inferences about past cultures to which we do not have as immediate and complete access. Thus, stone tools found at archaeological sites in Europe could be recognized as tools rather than naturally formed rocks only when they were seen as akin to the stone tools used by contemporary Native Americans. Similarly, Wason argues, SETI scientists may misidentify signs of extraterrestrial intelligence. The challenge, then, is to seek a wide enough array of analogies that scientists can come to recognize manifestations of extraterrestrial intelligence, even when they resemble a naturally occurring phenomenon.Once we have those analogies, Wason argues, we will also need to have an “intellectual context” that enables us to identify signs of intelligence. Only when people took seriously the possibility that chipped rocks might be prehis-toric tools were they predisposed to look for them. Until then, this core piece of evidence for reconstructing extinct civilizations was simply overlooked by archaeologists doing fieldwork in Europe. The difficulty of recognizing the unanticipated, Wason suggests, may provide a solution to the Fermi paradox, which asks, “If extraterrestrial intelligence exists, why haven’t we found it?” Wason answers this question by noting that we have been unable to free ourselves sufficiently from our preconceptions of extraterrestrial intelligence to recognize its existence.As we assemble the varieties of data from which we will judge whether we have made contact with extraterrestrial intelligence, Wason reminds us of the utility of the “cabling” method of reasoning, in which any single piece of evidence may in itself come up short, like the strands of a cable that each run only part of the cable’s full length. Nevertheless, by recognizing that a solid argument—like a solid cable—may be made up of elements that are in themselves not sufficient to determine the artificiality of a signal, but that when intertwined may be strong, we may be open to recognizing intelligence where we might otherwise miss it.While Wason recognizes many problems of interpreting symbolic sys-tems—in which “signs” stand in an arbitrary relationship to the ideas they signify—he also maintains that we may be able to get a general sense of the intent of a message, even if we cannot divine its specific meaning. Indeed, he suggests that even our ability to detect purposive agency may be an evolved trait, which may be shared by intelligent beings on other worlds, making it plausible that even if we cannot understand what another civilization is trying to say, intelligent beings may have the capacity to recognize that someone is saying something.

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