Lasers reveal sites used as the Americas’ oldest known star calendars

Olmec and Maya people living along Mexico’s Gulf Coast as early as 3,100 years ago built star-aligned ceremonial centers to track important days of a 260-day calendar, a new study finds.

The oldest written evidence of this calendar, found on painted plaster mural fragments from a Maya site in Guatemala, dates to between 300 and 200 B.C., nearly a millennium later (SN: 4/13/22). But researchers have long suspected that a 260-day calendar developed hundreds of years earlier among Gulf Coast Olmec groups.

Now, an airborne laser-mapping technique called light detection and ranging, or lidar, has revealed astronomical orientations of 415 ceremonial complexes dating to between about 1100 B.C. and A.D. 250, say archaeologist Ivan Šprajc and colleagues.

Most ritual centers were aligned on an east-to-west axis, corresponding to sunrises or other celestial events on specific days of a 260-day year, the scientists report January 6 in Science Advances.

The finding points to the earliest evidence in the Americas of a formal calendar system that combined astronomical knowledge with earthly constructions. This system used celestial events to identify important dates during a 260-day portion of a full year.

“The 260-day cycle materialized in Mesoamerica’s earliest known monumental complexes [and was used] for scheduling seasonal, subsistence-related ceremonies,” says Šprajc, of the Research Center of the Slovenian Academy of Sciences and Arts in Ljubljana. “We cannot be certain exactly when and where it was invented.”

Some of the oldest ceremonial centers identified by lidar clearly belong to the Olmec culture, but others are hard to classify, says archaeologist Stephen Houston of Brown University in Providence, R.I., who did not participate in the new study.

Olmec society dates from around 3,500 to 2,400 years ago. Links between the Olmec and later Maya culture, known best for Classic-era cities and kingdoms that flourished between roughly 1,750 and 1,100 years ago, are unclear. But Classic Maya inscriptions and documents also reference the 260-day calendar.

Mobile groups in Mesoamerica, an ancient cultural region that extended from central Mexico to Central America, may have scheduled large, seasonal gatherings using the 260-day calendar long before it gained favor among Classic Maya kings, Šprajc and colleagues suggest.

The same calendar may also have marked days of important agricultural activities or rituals as maize cultivation spread in Mesoamerica starting around 3,000 years ago, they add. Some Maya communities still use a 260-day calendar to organize maize cultivation and schedule agricultural rituals.

Previous lidar data indicated that ceremonial centers based on a common blueprint appeared at many Olmec and Maya sites along Mexico’s Gulf Coast by about 3,400 years ago (SN: 10/25/21). Only now has the calendrical significance of ceremonial centers’ alignments become apparent.

The most common architectural alignment detected in the new study corresponded to the position of sunrises on February 11 and October 29 when complexes were in use, separated by 260 days. These complexes faced east toward a point on the horizon where the sun rose on those two days.

Another frequent orientation matched sunrises separated by 130 days, or half of the 260-day count.

A minority of ceremonial complexes were aligned with dates of solstices (longest and shortest days of the year), quarter days (the midpoint of each half of the year) or lunar cycles in the 260-day year. Other centers tracked the position of Venus, a star associated with the rainy season and maize farming.

Sunrises or sunsets recorded at ceremonial centers were typically separated by multiples of 13 or 20 days. Aside from representing basic mathematical units of a 260-day year, the numbers 13 and 20 have long been associated with various gods and sacred concepts among Maya people and other Mesoamerican groups, Šprajc says.

Future excavations at lidar-detected ceremonial complexes can investigate whether ancient groups formally dedicated certain structures to specific days in the 260-day year, Houston says.

Ice Age Hunting Camp Identified in Mexico

This story begins anywhere from 4,000 to 17,000 years ago, when woolly mammoths roamed the Earth. It picks up in Mexico in the mid-1950s, when the remains of a couple of those mammoths — and stone tools with traces of human use — were found in the central part of the country.

Now flash forward to the present day, when a recent study of those artifacts, using modern science and technology, is giving new glimpses into what researchers now believe was an Ice Age camp of humans in what is today México state.

“The study indicates that it was a seasonal hunter-gatherer camp,” archaeologist Patricia Pérez Martínez, author and coordinator of the project, said Tuesday during a presentation of the study’s findings.

The animal remains and artifacts, found nearly seven decades ago during a public works project in the small community of Santa Isabel Ixtapan, represent “the first material evidence of the existence of this type of site on the shores of Lake Texcoco, around 9,000 years ago,” Pérez said.

The findings are significant because small villages of humans in that time period usually existed in caves and rock shelters, often in mountainous regions, usually in the northern region of Mexico.

“Finding a seasonal hunter-gatherer camp in the open air is very [rare],” Pérez said. 

Indeed, the Santa Isabel Ixtapan site is the only one in the Valley of México with direct evidence of stone tools and mammoth bones, she added.

The first set of bones was found here in 1954, and then two years later, another mammoth’s remains, along with stone tools, were found about 250 meters away. Then, between 2019 and 2021, more bones and “possible mammoth traps” were discovered.

These days, in tribute to the area’s prehistoric past, there is a sculpture of the long-tusked, giant beast in the middle of a roundabout in Santa Isabel Ixtapan.

The research project, “Interaction of First Settlers and Megafauna in the Basin of México,” is a joint effort between INAH and the National School of Anthropology and History (ENAH), where Pérez heads the Hunter-Gatherer Technology Laboratory.

The effort to reevaluate the site was carried out with advanced technology tools and testing methods that Pérez said can lead to fresh findings about the landscape, megafauna (large animals) and human interactions with the surroundings.

Her hypothesis is that the ancient human inhabitants used and subsisted on the lake’s resources, which she said is supported by the discovery of small fragments of fish bone (seemingly cooked in some sort of charcoal) and obsidian microflakes (indicating residue from a stone that was possibly carved into a tool).

“Since the flakes are very small fragments, we hope that in the next [field research] session, scheduled for this year, we will be able to do extensive excavation that will give us a better context,” said Pérez.

“Likewise, in 2023, the soil samples will be studied in our laboratories, and the traces of use of the three tools found with the second mammoth — which are exhibited in the National Museum of Anthropology — will be analyzed,” she said. 

“Initially, they were thought to be hunting projectile points, but recently, more detailed observations place them as knives, possibly used for butchering.”

Ceremonial cave site from Postclassic Maya period discovered in Yucatán Peninsula

Archaeologists have discovered a ceremonial cave site in Chemuyil on the Yucatán Peninsula, Mexico, that dates from the Postclassic Maya period.

As is known during the pre-Hispanic era diverse cultures existed throughout the territory of Mexican, but it was the Maya one of the most prevalent and the one that left the greatest records of its passage.

The Maya believed that the universe was split into three parts: heaven, earth, and the underworld, with caverns serving as a conduit or gateway to Xibalba, a realm governed by the Maya death gods and their assistants.

The Instituto Nacional de Antropología e Historia (INAH) was notified of the site by personnel from the civil association Círculo Espeleológico del Mayab and the Urban Cenotes Project of Playa del Carmen, who identified archaeological remains whilst mapping cave systems in the region.

A team led by archaeologist Antonio Reyes was despatched to the site, where they discovered two vessels, one entire and the other broken, as well as a tripod bowl dating from the Late Postclassic Maya (1200–1550 AD).

The first is a Navulá-type monochrome vessel that still has one of its two handles, whilst the second is a globular pot, which was found fragmented because of tree roots that crushed the vessel against some rocks.

Both vessels were positioned in natural niches where water dripped down from stalactites, whilst the tripod bowl was placed face down and covered with stones.

The researchers believe that the bowl was a ceremonial offering, whilst the two vessels were used for the ritual collection of water from the stalactites.

Although there are no major Maya centers within Chemuyil, the people living in the area between Playa del Carmen and Tulum often used many of the natural cavities, cenotes, and cave systems for ceremonial purposes.

Did the Aztecs Use Mountains to Track the Sun?

Without clocks or modern tools, ancient Mexicans watched the sun to maintain a farming calendar that precisely tracked seasons and even adjusted for leap years.

Before the Spanish arrival in 1519, the Basin of Mexico’s agricultural system fed a population that was extraordinarily large for the time.  Whereas Seville, the largest urban center in Spain, had a population of fewer than 50,000, the Basin, now known as Mexico City, was home to as many as 3 million people.  

To feed so many people in a region with a dry spring and summer monsoons required advanced understanding of when seasonal variations in weather would arrive.

Planting too early, or too late, could have proved disastrous. The failure of any calendar to adjust for leap-year fluctuations could also have led to crop failure.

Though colonial chroniclers documented the use of a calendar, it was not previously understood how the Mexica, or Aztecs, were able to achieve such accuracy.

New UC Riverside research, published in the Proceedings of the National Academy of Sciences, demonstrates how they did it. They used the mountains of the Basin as a solar observatory, keeping track of the sunrise against the peaks of the Sierra Nevada mountains. 

“We concluded they must have stood at a single spot, looking eastwards from one day to another, to tell the time of year by watching the rising sun,” said Exequiel Ezcurra, distinguished UCR professor of ecology who led the research. 

To find that spot, the researchers studied Mexica manuscripts. These ancient texts referred to Mount Tlaloc, which lies east of the Basin.

The research team explored the high mountains around the Basin and a temple at the mountain’s summit.

Using astronomical computer models, they confirmed that a long causeway structure at the temple aligns with the rising sun on Feb. 24, the first day of the Aztec new year.

“Our hypothesis is that they used the whole Valley of Mexico. Their working instrument was the Basin itself. When the sun rose at a landmark point behind the Sierras, they knew it was time to start planting,” Ezcurra said.

The sun, as viewed from a fixed point on Earth, does not follow the same trajectory every day. In winter, it runs south of the celestial equator and rises toward the southeast. As summer approaches, because of the Earth’s tilt, sunrise moves northeast, a phenomenon called solar declination. 

This study may be the first to demonstrate how the Mexica were able to keep time using this principle, the sun, and the mountains as guiding landmarks.

Though some may be familiar with the “Aztec calendar,” that is an incorrect name given to the Sun Stone, arguably the most famous work of Aztec sculpture used solely for ritual and ceremonial purposes. 

“It did not have any practical use as a celestial observatory. Think of it as a monument, like Nelson’s Column in Trafalgar Square or Lincoln’s Memorial in Washington, D.C.,” Ezcurra said. 

Learning about Aztec tools that did have practical use offers a lesson about the importance of using a variety of methods to solve questions about the natural world. 

“The same goals can be achieved in different ways. It can be difficult to see that sometimes. We don’t always need to rely solely on modern technology,” Ezcurra said. “The Aztecs were just as good or better as the Europeans at keeping time, using their own methods.”

The Aztec observatory could also have a more modern function, according to Ezcurra.

Comparing old images of the Basin of Mexico to current ones shows how the forest is slowly climbing up Mount Tlaloc, likely as a result of an increase in average temperatures at lower elevation. 

“In the 1940s the tree line was way below the summit. Now there are trees growing in the summit itself,” Ezcurra said. “What was an observatory for the ancients could also be an observatory for the 21st century, to understand global climate changes.”

Maya Statue Discovered in the Yucatán

An imposing, life-size sculpture of a headless human found during excavation work for the Maya Train has been temporarily nicknamed “Yum keeb” — the god of the phallus or fertility. 

The finding occurred in the state of Yucatán in the archaeological zone of Oxkintok, about 55 kilometers south of Mérida. The limestone statue without a head, hands, lower legs and feet measures 1.65 meters tall, or about 5 feet 5 inches.

“He was found lying on his back and represents the human figure,” archaeologist Luis Pantoja Díaz said during a media tour of the area on Wednesday. “We see the marked pectorals, the middle part that could be the hanging belly and the part of the member.”

He also said one could see buttocks (which are clearly visible in the photo) and some lines on the back, such as those that delineate shoulder blades (which are not).

While the newspaper La Jornada used the terms falo (phallus) and miembro (member) in describing the figure, another newspaper reported nothing along those lines, or about fertilidad (fertility), explaining instead that the sculpture is that of a warrior.

Its lack of a head “surely represents a warrior who was a prisoner in combat,” said Diego Prieto, general director of the National Institute of Anthropology and History (INAH), as quoted by El Financiero.

Both sources said the sculpture was possibly used as an offering to the gods. It was found near a hieroglyph-laden staircase that was being cleaned and restored.

Pantoja Díaz stressed that the figure is still being analyzed to determine its specific function, thus the “temporary” nickname. Even the statue’s status as the representation of a male is not 100% assured, he added.

Oxkintok was a Maya city that existed in the latter portion of the Mesomerican Classic Period (A.D. 250 to 900) and was the capital of the region before the emergence of Uxmal. Noted for its historical markers, such as pyramids and monuments, it is nestled among mountains that are covered in undergrowth — with lots of potential discoveries still to be made.

The Maya Train has been divided into seven sections and the INAH reportedly has completed its excavation work in sections 1-3 and 5, with No. 4 to be completed soon and sections 6 and 7 in the prospecting stage.

“We have uncovered information that will nourish the knowledge of the Mesoamerican Maya world for at least the next two decades,” said Prieto, the INAH director. “This work will undoubtedly impact the study of Maya cultures … over many, many years.”

Overall, according to INAH data through Dec. 6, findings on the entire Maya Train route include 31,306 structures including foundations, 1,541 ceramics and chiseled stones, 463 sets of bones or skeletons, 1,040 natural features such as caves and cenotes, 708,428 ceramic figures and fragments (from sections 1-4) and 576 pieces in the process of analysis.

The Maya Train, one of President Andrés Manuel Lopéz Obrador’s most ambitious projects, and one that has been challenged by various problems and issues, will pass through Tabasco, Chiapas, Campeche, Yucatán and Quintana Roo.

Originally budgeted for nearly US $8 billion in 2020, it has now ballooned to up to US $20 billion, according to reports.

Last month, AMLO was quoted as saying that “the largest [current] railway project in the world” at 1,550 kilometers (963 miles) will be completed “in December 2023.”