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Architecture, Astronomy, and Calendrics in Pre
Columbian Mesoamerica

Vincent H. Malmstrom *

INTRODUCTION

It has long been recognized by archaeologists working in Mesoamerica that
the great pre-Columbian ceremonial centers of this region were the
consciously planned products of societies with highly developed
architectural sensitivities. The design and construction not only of
individual buildings or complexes but also, on occasion, of entire cities
are known to have been carried out with careful attention to such concepts
as harmony, balance, and proportion. On the other hand, only relatively
recently has it begun to be appreciated that many of the architectural
alignments found in Mesoamerica appear to be related to the religious
and/or cosmological beliefs of the early civilizations which built them.
This tardy recognition of the correlation between architecture and
religion is all the more surprising when we pause to consider that most of
the monumental structures which these societies erected, be they pyramids,
temples, or ball courts, were meant to serve a religious function. And
because an almost obsessive preoccupation with the calendar and astronomy
was central to the spiritual lives of all Mesoamerican cultures (Miles
1965:284), it is only reasonable to expect that many structural
orientations within this region should reflect such astronomical events as
the equinoxes, the solstices, or the zenith passages of the sun. In spite
of this, an alignment which has frequently been encountered on the Mexican
plateau but not adequately explained to date is one that is oriented to an
azimuth approximating 285º, or about 15º north of west.

The foremost example of this alignment (which is skewed some 15º clockwise
from the cardinal points) is that provided by Teotihuacán, located
approximately 50 km northeast of the present city of Mexico. In its
heyday, which lasted from approximately the time of Christ until the
mid-seventh century of the Christian era, Teotihuacán was the largest
urban agglomeration anywhere in the New World. Indeed, synchronous with
Rome in Europe and Peking in Asia, it may have ranked as one of the three
most populous cities

*The author is especially indebted to Paul A. Dunn, Dartmouth Class of
1981, for his assistance in conducting measurements in the field, and to
Mark S. Fagan, Dartmouth 1980, for preparing the final maps.

in the world at the time. It owed its greatness to a congenial site on the
shore of a large lake which afforded both ease of transportation and
irrigation water for the rich alluvial soils of its semi-arid mountain
basin. Moreover, it was strategically located on a pass leading across the
mountains which fringe the Mexican plateau so that it could effectively
command the exchange of goods between the cooler, drier uplands to the
west and the warmer, moister lowlands to the east. At its peak,
Teotihuacán was a thriving metropolis of well over 50,000 inhabitants
(some estimates place the city's population as high as 100,000 to
200,000), but a city which--as Millon has emphasized -- was as much a
religious center as it was an economic node (Millon 1973:54-59).

As the configuration of this great city was revealed during the
Teotihuacán Mapping Project in the 1960s and 1970s, it was realized that
its principal thoroughfare--a grandiose avenue called the "Street of the
Dead" by the Aztecs--was oriented 15.5º east of north, and that a grid
system having this same alignment had been superimposed on all of the
surrounding countryside. Even the drainage ditches separating the
productive, alluvial farm-plots or chinampas, that had been reclaimed from
the south end of the lake near present-day Xochimilco, display the same
well-ordered orientation (Coe 1964:96). Here was urban and regional
planning on a massive scale, but what was the principle behind it? Why had
the Teotihuacanos chosen to orient everything 15.5º off of north, rather
than to the cardinal points?

As early as 1945 Macgowan, in a brief note published in American
Antiquity, had commented on the fact that most pre-Columbian ceremonial
centers in Mesoamerica appeared to have been oriented east of north
(Macgowan 1945:118). He observed that orientations seemed to cluster in
three general groups: true north, about 7º east of north, and about 17º
east of north. From field measurements begun in 1971, Aveni was able to
confirm that 50 of 56 sites which he examined were indeed oriented east of
north, and that a 17º "family" of alignments did in fact seem to exist
(Aveni 1975:166).  Aveni also concluded that this particular pattern of
orientation seemed to be most prevalent in the Valley of Mexico and he
specifically mentioned Tenayuca, Tepozteco, and Tula as sites where this
alignment was encountered. (It should be pointed out that Aveni's "17º
family" of alignments includes orientations as far off as 15.5º, for he
includes Teotihuacán in this "group".)

Ever since the 15.5º alignment of the Street of the Dead at
Teotihuacán--and the consequent orientation of the front of the Pyramid of
the Sun toward an azimuth of 285.5º--was first recognized, numerous
explanations have been advanced to explain it. In 1967, Dow suggested the
setting position of the Pleiades as a possible motive for such an
orientation (Dow 1967:326-344), following the same line of thought as
Marquina and Ruíz had presented for the orientation of the Tenayuca
pyramid in 1934 (Marquina and Ruíz 1934:101-106). However, Dow also
considered the rising positions of both Sirius and Dubhe as possible
factors in the orientation of Teotihuacán as well. Heyden and Gendrop
(1975:39) stated that the Pyramid of the Sun is oriented toward the sunset
position on the day that the sun passes vertically overhead at
Teotihuacán, though this

can easily be shown to be 291.0º rather than 285.5º In the same year,
Heyden offered another possibility, suggesting that the Pyramid of the Sun
might be aligned in the same direction as the mouth of a cave which had
recently been discovered beneath the structure (Heyden 1975:131-147).
Summarizing the various hypotheses on orientation which had been advanced
up to 1975, Aveni also mentioned an unpublished idea of Drucker that the
Pyramid of the Sun might be oriented to solar positions which utilize
local topographic features (Aveni 1975:170), but he himself concluded
(Aveni 1977b:5) that "they (the Pleiades) must remain the prime candidate
for an astronomical motivation in the orientation of Teotihuacán." 

Aveni reached this conclusion after admitting in his earlier work that (1)
the Pleiades would have been "invisible well before they reached the
horizon of Teotihuacán" and (2) "the precessional motion of the Pleiades
is so rapid that a mistake of 100 years in the dating of the baseline is
equivalent to a shift of .5º in the azimuth of the setting point" (Aveni
1975:169). Recognizing the latter point as a particularly critical flaw in
the "Pleiades hypotheses," Aveni has had to dismiss all later sites built
on the Mexican plateau having similar orientations to Teotihuacán (such as
Tenayuca, Tepozteco, and Tula) as being simply "non-functional imitations"
of the great Mesoamerican metropolis (Aveni 1975:170).

More recently (1978), Aveni and his associates have investigated the
distribution of "pecked cross symbols" in Mesoamerica, most of which are
located on the Mexican plateau near Teotihuacán, and some of which seem
"to have been modified to fit the overriding architectural plan" (Aveni et
al. 1978: 279). On the basis of these observations, Aveni concludes that
"Teotihuacán North" was more important than "astronomical north" and that,
apart from the "surprising" discovery of similar symbols in the Petén
region of Guatemala, the "data are consistent with an origin in and
diffusion from the classic Teotihuacán empire" (Aveni et al. 1978:279).
The fact that some of the symbols are composed of approximately 260
elements further suggests that they may have been related to the
ritual-count of 260 days that was used throughout preColumbian Mesoamerica
(Aveni et al. 1978:267-269).

As a result of fieldwork completed in early 1979, the present author has
been able to confirm alignments to an azimuth of ~285º not only at several
sites on the Mexican plateau but in the Yucatán, Petén, and Oaxaca regions
as well. These observations were refined and augmented by data kindly
supplied by Professor A. F. Aveni (personal communication 1979) and are
tabulated in Table 22.1. Although no claim can be made for the
completeness of the survey, the principal conclusions which can be drawn
from the distribution which emerges are that (1) virtually all regions of
Mesoamerica are represented and (2) sites ranging in age from 1000 B.C. to
well into the Classic Period (A.D. 300-900) are included. In the
discussion to follow, a brief resumé is given of only the major sites
which have been identified elsewhere than on the Mexican plateau.

Thanks to the work of Matheny (1976:639-640), it is now known that the
ceremonial center of Edzná in the southwestern part of the Yucatán
peninsula was a large and thriving urban agglomeration as early as 150
B.C. It was thus essentially synchronous with Teotihuacán. It is
interesting to note that the major structure at Edzná - a five-story
pyramid known in Spanish as "Cinco Pisos"--is squarely oriented to an

azimuth of 285.5º, and as the map prepared by Andrews reveals (Aveni
1975:257), a similar orientation is shared by many other structures at the
site.

At Chichén Itzá, Toltec reconstruction has altered most of the buildings
on the northern side of the site, but several of those on the southern
side, such as Chicchan Chob and the House of the Deer, show a 285º
orientation. The observatory, or Caracol, is an especially interesting
case, for the older Maya core of the building has the mid-line of its
front window (Window 1) oriented squarely toward 285º whereas the
encircling platform and front stairway added by the Toltecs (Gendrop
1972:151) faces directly toward the summer solstice sunset.

Although individual structures at a number of smaller sites demonstrate
orientations approximating 285º, it is perhaps significant that in many of
the later and more peripheral ceremonial centers of the Maya cultural
realm fewer and less important structures seem to share this alignment, as
though suggesting that the "vogue"  for such orientations gradually tended
to die out both with time and distance. For example, at such recent
centers as Palenque and Comalcalco on the western edge of the Maya area,
no structures at all were found which were aligned to 285º.

THE ASTRONOMICAL MATRIX AT TIKAL

The largest and most impressive ceremonial center constructed by the Maya
is undoubtedly Tikal, located in the rainforest of Petén, the northernmost
department of Guatemala. It is dominated by five great pyramids, all of
which reach or exceed 60 m in height. Although each of these structures is
architecturally interesting in its own right, it is their spatial
relationship to each other that is of paramount importance to any
appreciation of the astronomical significance of the site. Radiocarbon
dating of the lintels found in the pyramid superstructures reveals that
Temples I, II, and V were all completed about A.D. 700, whereas Temple IV,
the highest, was completed about 741 and Temple III was finished about
810. The range in completion dates, although spanning more than a century,
should not obscure the possibility that the entire ensemble may have been
planned as an integrated complex. The reason for thinking this is that
Temples I and II face each other across the 80-m wide Great Plaza on an
axis which runs 9º clockwise of a true east-west alignment (i.e.,
99-279º), but Temple I is offset just enough to the north of Temple II so
as to afford an unobstructed view of Temple IV some 730 m to the west. The
roof comb of Temple II is also the lowest of the five pyramids, suggesting
that although the structure lends symmetry to the Great Plaza, it was not
intended by either its height or its distance from Temple I to serve any
astronomical function. (The fact that the edifices fronting on the Great
Plaza are oriented 9º off of the cardinal points may reflect a magnetic
alignment extant in the eighth century; today the magnetic variation in
the Petén averages 5º E.)

Once the spatial arrangement of the four most widely separated pyramids is
mapped, it becomes apparent that Temple I served as the anchor-point of a
relatively sophisticated astronomical matrix. A sight-line between the
doorways of Temples I and IV marks an azimuth of 285º, whereas one between
the doorways of Temples V and I

TABLE 22.1

STRUCTURES ORIENTED TO ~285º a

General Region Site Time-Frame Structure
Orientation Measurement

Mexican plateau    
Teotihuacán     A.D. 0-650    Pyramid of the Sun    Front  *285.5º   (M)
Tula            A.D. 950-1150       Temple B        Side    287.1º (A)
Tenango         A.D. 650      Principal Structure   Side    283.7º (A)
Xochicalco      A.D. 650   Temple of Plumed Serpent Front   286.8º (A)

Yucatán               
Edzná       150 B.C.-A.D. 850    Cinco Pisos        Front  *285.5º (M-D)
Sayil           A.D. 600 (?)     Main Palace        Side    282.4º (A)
Labná           A.D. 600 Temple of Columns: Mirador Side    282.1º (A)
Kabáh           A.D. 600         Codz Pop           Front   283.6º (A)
Mayapan         A.D. 900-1300    Observatory: (152) Front   282.8º (A)
Temple of Sacrifices (151) Side    282.8º (A)
Izamal          A.D. 600 (?)     Platform, Pyramid
of Kinich-Kakmo    Side    287.2º (A)
Chichén Itzá    A.D. 700-1300    Chicchan Chob      Front   285.0º (M-D)
House of the Deer  Side    285.0º (M-D)
Caracol (mid-line -Window)  Front  *284.9-285.7º(A)
Cobá            A.D. 600         XV, XVI            Side    285.0º (M-D)
Kohunlich       A.D. 600         Ball-court   (Main axis)   285.0º (M-D)
Chicanná        A.D. 450         Groups C and E     Side    283.0º (M-D)
Becán           A.D. 450         East Group (I, IV) Side    283.0º (M-D)
II, III            Front   283.0º (M-D)

Belize-Petén        
Altun Ha        A.D. 600 (?)     Structure A-5      Front   285.0º (M-D)
Tikal           A.D. 200-900     Alignment of Temple
I to Temple IV     Front  *285.0º (M-D)
Alignment of Temple
I to Temple V (RightAngle) 15.0º (M-D)

Oaxaca 
Monte Albán 600 B.C.-1100 A.D.   Mound Y            Front   285.0º (M-D)
Huamelulpan     300 B.C.- ?      Main Pyramid       Front   285.0º (M-D)

Gulf Coast
La Venta       1000-600 B.C.     Stirling "Acropolis" & 
"Plaza"  Side             *285.0º(B)

a -- The present author has chosen to re-define Aveni's "17º family" of
alignments as the "15.5º family" inasmuch as the principal structures in
the major sites of Mesoamerica appear to center on this value; see
asterisked items above.

b -- Sources of measurements: A--Aveni; B--Bernal; M--Millon;
M-D--Malmström and Dunn. Inasmuch as the author and his assistant carried
out their measurements with a surveyor's compass, wherever data obtained
by more precise instrumentation are available, they are cited
instead--rounded to a tenth of a degree.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

marks a right-angle to this, namely 15º (Fig. 22.1). Thus the placement of
both Temples IV and V appears to commemorate the same recurrent alignment
found in the ceremonial centers of the Mexican plateau and of the Yucatán
peninsula. In addition, however, a sight-line between the doorways of
Temples I and III demarcates a true east-west line and therefore the axis
of equinoctial sunrise and sunset. Moreover Temple III is so located (ca.
280 m west of Temple I and 400 m southeast of Temple IV) that the middle
of its roof-comb breaks the horizon precisely at an azimuth of 115º as
seen from the doorway of Temple IV, permitting an accurate calibration of
the sunrise position at the winter solstice. Thus, two of the great
pyramids at Tikal are keyed to alignments related to 285º and a third
apparently is situated so as to serve both as an equinoctial and
solsticial marker. When one is aware that Tikal constitutes not only the
Mayas' crowning achievement in architecture, engineering, and artistry but
also a brilliantly conceived and superbly executed astronomical and
calendrical matrix, one cannot but stand in yet greater awe of their
outstanding abilities and accomplishments.

SITES IN THE OAXACA AND GULF COAST REGIONS

Having confirmed the presence of architectural alignments toward an
azimuth of 285º at both extremities of Mesoamerica (i.e., on the Mexican
plateau in the west and in the Yucatán and Petén regions in the east), the
author was encouraged to investigate the possibility of similar
orientations in intervening geographic areas such as the highlands of
Oaxaca and the coastal lowlands bordering on the Gulf of Mexico. The
former region constitutes the core area of both the Zapotec and Mixtec
peoples, and one key site in each cultural realm was selected for field
study. For the Zapotecs, the site selected was Monte Albán, located on the
top of a mountain overlooking the modern city of Oaxaca;  for the

Mixtecs, the ancient site of Huamelulpan in the district of Mixteca Alta,
some 100 km northwest of Oaxaca city, was chosen for study. In the Gulf
Coast region, the site of La Venta (the "capital" of the Olmecs), was also
examined for structural orientations with the help of a map.

Monte Albán dates back to at least 600 B.C. and has been rebuilt in whole
or in part several times during its long history. Today virtually all of
the mountain-top site conforms to a rigid symmetry oriented to an axis
running about 5º east of north. The only structure that deviates markedly
from the overall layout is an arrowhead-shaped edifice known as Mound J.
Because of its strange configuration and its lack of conformity with the
remaining structures in and around the Great Plaza, Mound J has been
interpreted as an "observatory," and Aveni has argued that its orientation
toward an azimuth of 45º commemorates the heliacal rising of the star
Capella, which heralds the passage of the vertical sun over Monte Albán.
In support of his contention, Aveni observes that there is a zenith-tube
located in Mound P, a structure situated directly to the northeast of
Mound J. Without challenging this explanation, one can only wonder what
Mound J originally looked like, for it is known to have been rebuilt about
the time of Christ and was also probably involved in the total renovation
of the site which occurred about A.D.  600. In any event, neither Mound J
nor any other structure in and around the Great Plaza demonstrates an
alignment toward 285º. Nevertheless, lying half a kilometer to the
northeast of the Great Plaza on a lower ridge of the same mountain is a
structure known as Mound Y; its orientation is visibly at variance from
the general plan of the site even at a distance. Although some restoration
of Mound Y has taken place, the largest stones (comparable to those used
in the construction and reconstruction(s) of Mound J)  which form the
foundation platform for the temple have quite obviously not been moved
since they were first set in place. Thus Mound Y appears to have been one
of the earliest buildings to have been erected at Monte Albán but, unlike
Mound J, it does not seem to have been rebuilt on the two occasions that
the Great Plaza was reconstructed.  It is in all likelihood the oldest
structure on the site that still retains its original alignment.
Significantly, the front of the platform of Mound Y was found to face
squarely toward an azimuth of 285º.

The site of Huamelulpan in the Mixteca Alta district is a far more remote
and modest site than Monte Albán. In fact, it consists today of no more
than one partially excavated and restored temple. Although the upper walls
of the temple have been largely destroyed through centuries of neglect and
agricultural activity, the lower foundation is still solidly in place. The
southeast corner of the temple is especially interesting, because it is
composed of several massive, well-dressed stones measuring up to 2 m in
length, almost 1 m in width, and about 0.5 m in thickness. There one finds
a beautifully preserved carving of a lizard, underlain by calendrical
symbols that pre-date the initiation of the Long Count (i.e., at least
going back before the third century B.C.).  Once again the front of the
temple foundation was found to be oriented precisely toward an azimuth of
285º.

Because accurate field studies of some of the most ancient ceremonial
centers of Mesoamerica (namely those erected by the "Mother Culture" of
the region, that of the Olmecs) were precluded in this survey, it was
decided to utilize the site map of La Venta, an accessible reproduction of
which is found in a publication by Bernal (1969:34). Although it has been
known ever since the site was first excavated by Stirling that its
principal orientation lay 8º west of true north, what has apparently been
overlooked is the fact that the structures that comprise the so-called
Stirling "Acropolis" and Stirling "Plaza" are aligned some 23º to the east
of that axis. In other words, the Stirling "Acropolis" looks 15º east of
north, while its northwestern face is oriented once again toward an
azimuth of 285º (Fig. 22.2). Although the discovery of this alignment at
Monte Albán pushed the origin of this "innovation" back at least as far as
600 B.C., its presence at La Venta means that even the Olmecs were
commemorating this orientation as long ago as 1000 B.C.!

THE MEANING OF THE 285º ALIGNMENT

Because many of the sites listed in Table 22.1 were either synchronous
with Teotihuacán or preceded it, the possibility that the pattern of
orientation toward an azimuth of 285º originated in or diffused from that
great pre-Columbian metropolis is thereby ruled out. Furthermore, the
geographic distribution of 285º orientations occurs through such a broad
zone of latitude (roughly 5-8º depending on which sites are being
included) that a stellar association of any kind must be totally
discounted.  Similarly, they are found through such a wide longitudinal
range that a uniform magnetic alignment is likewise precluded. The
variation within Mesoamerica currently exceeds 5º between the easternmost
reaches of the Yucatán and the westernmost areas of the Mexican plateau. A
lunar association with an azimuth of 285º is also quite unlikely, because
only the most extreme moonset positions are easily definable, and in the
northwest quadrant of the sky these occur at approximately 290º and 300º.
Therefore, unless one is willing to discount all such 285º orientations as
coincidences, one must ascribe a solar origin to them, for no other
explanation can be advanced which is both spatially and temporally
consistent through the whole of Mesoamerica during a time span of well
over 2000 years.

Because the azimuth of 285º demarcates a point on the western horizon some
15º north of west, it is apparent that it must commemorate a sunset
position at a time of the year when the sun is overhead in the northern
hemisphere--i.e. between the vernal equinox (March 21) and the autumnal
equinox (September 21). Obviously, because this is not the summer solstice
sunset position--an azimuth that averages 295º throughout the Mesoamerican
region--it could commemorate a date either before June 22 or after it.
With the assistance of a solar ephemeris or a nautical almanac one can
determine that an average sunset position of 285.5º is recorded throughout
Mesoamerica before the summer solstice on April 30-May 1, and after the
summer solstice on August 12-13.2 Of these two possibilities, the latter
is definitely the more interesting to students of Mesoamerican calendrics.
This is because the Maya--the most highly advanced of all Mesoamerican
peoples in the realm of astronomy--believed that the present era of the
world began on August 13, 3114 B.C., according to the
Goodman-Martinez-Thompson correlation between the Maya and Christian
calendars. Ironically, Thompson himself dismissed the correspondence
between the beginning date of his correlation and an astronomical origin
for the most ancient of Mesoamerican calendars, the 260-day ritual
almanac, as being coincidental (Thompson 1960:98). However, recurrent
building alignments throughout Mesoamerica appear to commemorate a date
which can only have had astronomical (i.e., solar) origins or, at the very
least, could only have been established by astronomical means--i.e., by
counting the number of days from some fixed point in time. (In the latter
regard it should be pointed out that the August 13 sunset position could
easily have been defined simply by counting 52 days from the summer
solstice.) In the light of the evidence at hand, one can conclude that far
from being just one more in a series of "coincidences," the correspondence
of building alignment azimuths throughout Mesoamerica and the beginning
date of the Goodman-Martínez-Thompson correlation should more
realistically be considered as additional proof of the validity of the
latter. (3)

If the 285º architectural alignments indeed lend support to the Goodman
Martínez-Thompson correlation, they also perforce support the argument
that the "beginning of time" as defined by the Maya actually commemorates
an astronomical event--not necessarily a one-time "happening" but some
solar occurrence which is replicable every August 13. It is highly
unlikely, however, that sunset on that day, in and of itself, would be
sufficient cause to initiate a calendar such as the 260-day sacred
almanac. In that case it would be far more likely that the explanation
first put forward by Nuttall in 1928 is the correct one. She argued that
the 260-day count probably could be traced to the interval between
vertical sun positions at the latitude of Copán, the Mayas' principal
astronomical center, located just south of the fifteenth parallel of
latitude in the mountains of western Honduras (Nuttall 1928). This
argument won further support from Merrill who remarked on the
correspondence between the first zenith passage of the sun

at Copán (i.e., August 13) and "the beginning of time" as calculated by
the Goodman Martínez-Thompson correlation (Merrill 1945:307-311). However,
both arguments were dismissed by Thompson, who preferred to believe that
the 260-day almanac was either (1) an approximation of the human gestation
period, or (2) simply a permutation of the numbers 13 and 20, both of
which had magical significance to the Maya (Thompson 1960:98-103).
(Obviously, if one adopts either of the latter explanations, an August 13
beginning for the sacred almanac has to have been a coincidence.) Even so,
one is left wondering whose gestation period was so important as to
commemorate it, and specifically how did one decide when it actually
began? Or similarly, what day was so remarkable that a series of
permutations of 13 numerals with 20 day-names was initiated on that date
and none other?

Although both Nuttall and Merrill were correct in pointing out that the
sacred almanac could be accurately calibrated at Copán, they were wrong in
hypothesizing that the 260-day count had actually begun there. In an
earlier paper, I have demonstrated that both geographical and historical
arguments can be raised against such a contention (Malmström 1973:939). On
the first score, they appear to have overlooked a very cogent observation
made by the German naturalist Gadow in 1908 and cited by Thompson (Gadow
1908:303). Gadow argued that the 260-day count must have begun in a
tropical lowland region because several of its day-names commemorate
animals such as the alligator, monkey, and iguana; none of these is native
to the highland ecological niche of oak and pine forests where Copán is
situated. On the second score, they both seem to have been unaware that
Copán was a relatively recent ceremonial center, whereas the sacred
calendar was a very ancient creation. Morley, for example, points out that
the oldest dated monument at Copán goes back only to A.D. 465 (Morley
1946:59), while also contending that the ritual almanac must have been
devised at least as early as the fourth century B.C. (Morley 1946:47).
Even if one accepts Morley's relatively conservative estimate of the
calendar's age, one is confronted with a hiatus of at least eight
centuries between the time when the count supposedly started and the
ceremonial center of Copán was founded. It was for these reasons,
therefore, that I was prompted to look for a tropical lowland site on the
same parallel of latitude as Copán but of sufficient antiquity to qualify
as the birthplace of the 260-day sacred almanac. This I identified as the
large ceremonial center known as Izapa, located on the Pacific coastal
plain of Mexico adjacent to the Guatemalan border. Here a tropical
rainforest environment surrounds a site whose earliest radiocarbon date
goes back to 1500 B.C. (Ekholm 1969:1).

Therefore, if the alignments of buildings throughout Mesoamerica to an
azimuth of 285º do indeed commemorate the sunset position on August 13,
they not only help to confirm the validity of the
Goodman-Martínez-Thompson calendar correlation, but they also testify to
an astronomical origin for the calendar on which it is based.  Moreover,
they conclusively restrict the geographic origin of that calendar to a
location where the date of August 13 was locally significant--in other
words, just south of the parallel of 15º north latitude. Ironically, the
285º alignments provide precisely the kinds of clues that Thompson argued
the 260-day almanac did not provide. For example, Thompson wrote

that there were "serious drawbacks" to the thesis that the 260-day count
represented the interval between zenith sun positions because this
interval varies across Mesoamerica from 260 days on the south to 311 days
on the north: "One must assume, then, that the cycle of 260 days
originated on the periphery of the area in which it was current, and that,
spreading northward and westward, it was eagerly adopted by peoples for
whom it had no solar significance" (Thompson 1960:98). That, in fact,
seems to be exactly what happened, for orienting one's buildings and
ceremonial centers to an azimuth that had no meaning except at the
latitude of Izapa must have been a learned pattern of behavior which
diffused along with the ritual almanac itself.  Thompson wrote further
that "there is absolutely no evidence that the 260-day cycle originated in
the vicinity of Copán or anywhere along latitude 14º30' which is on the
periphery of the area it covered" (Thompson 1960:98). Yet that evidence
has lain undiscovered and unappreciated all these years in the very
alignments of the great religious edifices and ceremonial centers
themselves. Indeed, there are probably few other regions of the world
where the principles of architecture, astronomy, and calendrics found so
intimate and dramatic a blending as they did in pre-Columbian Mesoamerica.
Today, as we gaze at the grid pattern rigidly superimposed by Teotihuacán
on the valley of Mexico or the majestic pyramids rising out of the
rainforest at Tikal, we must marvel anew at the complementary roles which
science and religion played in the lives of these now-dead civilizations.

Finally, we must recognize in this diffusion of almanac and architectural
alignments a spatial-temporal scenario that is perfectly consistent with
an Izapa-based point of origin. In an earlier publication (Malmström
1978:105-116), I presented a reconstruction of the chronology of the
Mesoamerican calendrical systems that now gains further support from these
architectural findings. For example, if La Venta was commemorating August
13 at 1000 B.C., it is obvious that the calendar must already have been
well established by then. Indeed, my reconstruction postulated an origin
in the fourteenth century B.C. (Malmström 1978:108). This suggests that a
fairly rapid diffusion had taken place through the lowland corridor of the
Tehuantepec Gap into what has been called the "metropolitan area" of the
Olmecs (Bernal 1969: 16), and that thereafter it had spread into the
highlands of Oaxaca, reaching the Mexican plateau sometime before the
birth of Christ. About the same time it was showing up in Edzná, the first
great urban center of the Maya; it then gradually diffused east and
southwards to reach such peripheral areas as Chichén Itzá and Copán. (Fig.
22.3 presents a hypothetical reconstruction of the diffusion pattern of
the 260-day sacred almanac.)

Because no calendrical inscriptions have been found at La Venta, we must
turn instead to Monte Albán, which has the oldest recorded dates of any
site in Mesoamerica (ca. 600 B.C.). It was for this reason that Caso was
led to hypothesize that the calendar had, in fact, first been developed
there (Caso 1971:333-348). But neither at Monte Albán nor at Huamelulpan
(where the dating has been given as 300 B.C.) has any evidence of the Long
Count been found (Broda de Casas 1969:80, 83). The latter represents the
fusion of the 260-day almanac with the 265-day secular calendar in such a
way that it records both

a number and a day-name in each of the counts. (For example, in the Long
Count a day would be known as 4 Ahau 8 Cumku, the first number and name
being its designation in the sacred almanac and the second being its
position in the secular calendar;  prior to the initiation of the Long
Count the same day would have been recorded simply as 4 Ahau.) The
earliest Long Count dates yet discovered record events around the time of
Christ, suggesting that it did not come into use until some time between
300 B.C. and A.D. 0; again, this conclusion is entirely consistent with my
earlier reconstruction, which had

pinpointed a date of 235 B.C. for its inception (Malmström 1978:108).
Unlike the 260 day almanac, however, the Long Count was never adopted in
the highlands of Oaxaca or on the Mexican plateau, and remained confined
almost entirely to the Maya dominated areas of Mesoamerica. Similarly, the
notational system used to record calendrical dates shows a corresponding
variation between the Oaxaca and Mexican plateau regions to the west--both
of which gradually came to employ only dots for numbers--and the Maya
culture realm to the east, where the original notational system employing
both dots and bars (the latter signifying a value of 5) continued in use
throughout pre-Columbian times.

CONCLUSION

It has long been known that the sacred 260-day calendar was utilized by
all of the pre Columbian civilizations of Mesoamerica, from the Maya in
the south and east to the Aztecs and Tarascans in the north and west. Only
recently has it been recognized that recurrent architectural alignments
centered on an azimuth of 285.5º are also spatially distributed over a
similarly extensive geographic area, ranging from the rainforests of the
Yucatán and Petén on the one hand to the semi-arid basins of the Mexican
plateau on the other. Because these alignments involve structures spread
over nearly 10º of latitude and almost 20º of longitude and were
constructed during a span of more than 2000 years, any astronomical
significance they may have would appear to commemorate a recurring event
that remained essentially unchanged throughout this expanse of space and
time. This event seems to have been sunset on the thirteenth of August, a
date which the Maya equated with "the beginning of time" in the
Goodman-Martínez-Thompson correlation. Because August thirteenth also
marks the southward passage of the zenith sun over the fifteenth parallel
of north latitude, initiating a 260-day period which ends on the following
May first when the northward passage of the zenith sun occurs at the same
place, there is the strong likelihood that these alignments not only
testify to the astronomical origins of the 260-day sacred calendar but
also to its specific geographic birthplace at the Early Formative site of
Izapa on the coastal plain of southeastern Mexico. A diffusion of the
sacred calendar from Izapa beginning in the fourteenth century B.C. is
perfectly consistent both spatially and temporally with what is known of
the ages of alignments of key structures at a number of major
archaeological sites distributed throughout the length and breadth of
Mesoamerica.

(2) At 0º horizon altitude, sunset positions on these dates vary from
285.4º at 13º N latitude to 286º at 20ºN latitude.

(3) Although at least nine other correlations have been proposed, none of
them comes within 40 days of the beginning date of the
Goodman-MartínezThompson correlation. In terms of sunset azimuths, the
closest approximation is some 8º away. The Spinden correlation, which is
the best known of the other systems, employs a starting date of October
15, when the sun is vertically overhead at approximately 8º south latitude
and its sunset azimuth is about 262º. (This article was published as
Chapter 22 of Archaeoastronomy in the Americas edited by Ray A.
Williamson, Ballena Press/Center for Archaeoastronomy, 1981, pp.249 261.)
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