Heaven and Earth in Ancient Mexico: Astronomy and Seasonal Cycles in the Codex Borgia by Susan Milbrath (review)

Pre-Columbian painted manuscripts or codices have fascinated Mesoamerican scholars for more than 100 years. Of the likely thousands that existed at the time of European contact, less than ten prehispanic examples are known to have survived. The interpretive argument presented in Heaven and Earth in Ancient Mexico focuses on only one of the extant manuscripts painted in the Mexican tradition known as the Codex Borgia.¹ In her preface, Milbrath states, “[T]his book proposes a new interpretation that emphasizes natural history, synthesizing data from the fields of ethnohistory, anthropology, art history, and archaeoastronomy to explore these complex images” (xi). The images to which she refers are those contained on pages 29 through 46 of Codex Borgia. Milbrath asserts more often than she argues throughout the book’s five chapters that (1) much of the iconography and calendrical information recorded in this section of the Borgia encodes a specific 365-day cycle of 18 seasonal festivals spanning the years 1495 and 1496, and (2) that these pages record a series of observable planetary bodies and astronomical events, most notable of which was a solar eclipse visible, weather permitting, across the central Mexican highlands.

The methodology that Milbrath employs was forged in similar, groundbreaking research conducted on almanacs in the Maya codices. Mesoamerican codices are comprised of highly condensed calendrical instruments called almanacs that place events of a secular and sacred nature into a 260-day ritual calendar. Maya codices contain explicit information (hieroglyphic texts and mathematical notations) that helps to elucidate an almanac’s function and calendrical structure. Expanded almanacs concern such natural events as the movement of astronomical bodies, the prediction of solar eclipses, and the commemoration of seasonal cycles. These instruments also include information that allows their calendrics reckoned in the ritual calendar to be situated into real time via the Maya Long Count and correlation to our Gregorian calendar. In a seminal article, the Brickers explain their method of triangulation: “[A]t least three different kinds of cycles are necessary in order to determine a unique date for an almanac. The first cycle is always the 260-day tzolkin [ritual calendar], and the second is usually the 365-day haab [solar year]. The third cycle must be astronomical.”² Epigraphical and iconographic references to seasonal stations or astronomical events provide the key to situating the calendrical cycles that are explicitly recorded or implied by imagery into real time.

The challenge of applying the Brickers’ triangulation method to Mexican almanacs requires inferring two of the three key pieces of information: Which of the multiple 365-day calendars used across central Mexico prior to European contact, if any, was used in Borgia almanacs, and which astronomical cycles, if any, is encoded in the imagery and calendrical structures of almanacs? Milbrath attempts to answer these questions for the Codex Borgia in the first half of her volume. Her arguments in Chapters 1 through 3, however, leave far too many possible alternatives, dangling issues, and unsubstantiated assertions.

Milbrath’s analysis depends on descriptions and explanations of Mexican calendar systems and an annual festival (veintena) cycle by Spanish clerics writing in the early colonial period. Scholars like Aveni question the accuracy of this data because of their Eurocentric influences.³ It is not so much the contents of these festivals as their ordering and rigid calendrical scheduling that are suspect. The reader arrives at the model for the Borgia’s “astronomical narrative” (76)—and its summation as presented in Chapters 4 and 5—with weak premises for dating and consequently for many of the iconographic and astronomical interpretations. Additionally, the presentation of results from astronomy software as though it were beyond dispute lends a false sense of precision not only for the interpretation of the Borgia imagery but also for the reconstruction of ancient cultural practices. The one big question left unanswered is why would the scribe of the Codex...