Shumla’s Hearthstone and Alexandria Projects – The Oldest ‘Books’ in North America

Shumla’s Alexandria and Hearthstone projects are transforming the Lower Pecos Canyonlands rock murals from awe-inspiring mysteries into a scientifically dated, digitally preserved, 4,000+-year visual tradition – a hunter-gatherer symbolic worldview.

Walk into a limestone rock shelter in the Lower Pecos Canyonlands and your sense of scale recalibrates. Above the line where daylight can reach, figures as tall or taller than a person spread across ceilings and walls. Red, black, yellow, and white shapes overlap rather than stand alone. Antlered forms, rabbits, felines, birds, serpents, and anthropomorphic beings crowd compositions so dense they feel less like “pictures” than like a system: bodies, colors, and gestures create a mysterious iconography.

Rock art documentation, Shumla Archaeological Research and Education Center.

For decades, archaeologists knew these murals were old. The question was how old, and whether the vast painted panels had accumulated slowly across centuries or arrived in concentrated periods of ritual labor. Rock art is famously hard to anchor in time; pigment sits on geology like with few obvious handles for dating. Without chronology, their interpretation remains unmoored in any evidentiary structure.

In the past few years, that has begun to change. Two interrelated projects led by the Shumla Archaeological Research & Education Center, one aimed at documentation and preservation, the other at chronology, are redefining the Lower Pecos murals as a part of a very lengthy intellectual tradition: a long-lived vision of the world, real and magical, expressed in paint and stone over more than four millennia.

Together, they are making the murals legible in a new way, scientifically dated, digitally recorded, and interpretable as one of the most continuous and significant graphic vocabularies created by hunter-gatherers anywhere in the world.

A painted landscape at a crossroads 

The Lower Pecos Canyonlands sit where ecological regions meet: the Edwards Plateau to the north and east, the Chihuahuan Desert to the west, and thorn scrub to the southeast. Three rivers -the Pecos, the Devils, and the Rio Grande – carve deep canyons through limestone and create hundreds of rock overhangs that shelter the pictographs. The archaeological record from more than 12,500 years of hunter-gatherer occupation is preserved in deposits in the rock shelters, from early big-game hunting to vegetable diets centered on harvested plants such as agave and sotol (desert spoon plant (genus Dasylirion).

The rock shelters and caves were not just places of habitation. In many Indigenous traditions, canyons, springs, caves, and sinkholes are not inert scenery but places of mystery – portals for the emergence of peoples and spirits, and reservoirs of power. The Lower Pecos is crowded with precisely these features, and the murals are often situated where the landscape itself adds weight to their presence. The murals, especially those made in what researchers call the Pecos River style, are technically ambitious. Panels can extend for more than twenty feet and to heights that would have required ladders or scaffolding to paint. The figures are interwoven and layered in ways that suggest planning rather than casual accretion, or a combination of the two.

This usage raises an important question: are we looking at a long, slow, deliberate composition that consciously reiterates a tradition? If so, was it based on seasonal, ceremonial, or another kind of social activity?

Answering that question requires a timeline strong enough to read coherently and bear interpretive weight.

Alexandria Project: preservation as scholarship

Anthropomorph with a power bundle. PRS pictographs from 41VV1230, Steelman KL, Boyd CE, Dering JP. Mapping the chronology of an ancient cosmovision: 4000 years of continuity in Pecos River style mural painting and symbolism. Sci Adv. 2025 Nov 28;11(48):eadx7205. doi: 10.1126/sciadv.adx7205. Epub 2025 Nov 26. PMID: 41296859; PMCID: PMC12652245

Before you can date or interpret a mural, you must know what is there—accurately, systematically, and at scale. This is the logic behind Shumla’s Alexandria Project, named for the ancient library and designed with a similarly archival ambition: to catalog and preserve the Lower Pecos murals with the planning and efficiency one would use to manage a collection of rare books.

The premise is simple and modern: rock art is not immune to time. Mineral accretions grow; pigments fade; surfaces spall; storms and flooding reshape micro-environments. Human impact, from unintentional touching to vandalism, adds its own pressures. Even under “good” conditions, loss is often incremental and therefore easy to underestimate until it becomes irreversible.

Alexandria addresses this by building a baseline digital record: high-resolution imagery, three-dimensional photogrammetry, and standardized metadata that allow murals to be studied, compared, and monitored over long periods. The archive is not a substitute for the original -but it is a form of continuity: if the wall becomes less readable, the record remains.

In practice, this preservation work also functions as foundational research. A region-wide database of motifs, attributes, and site documentation is not only a safeguard; it is a map of iconographic patterns. It lets researchers ask more precise questions: Where do certain motifs cluster? Which combinations recur? How does composition vary across canyons? What is rare, what is ubiquitous, and what styles can be identified?

Alexandria’s gift to scholarship is not merely a hard drive of images. It is a curated, organized corpus that can be interrogated by scholars today and in the future. Its detailed records enabled the second project: Hearthstone.

The Hearthstone Project: chronology through archaeology-based research

The Hearthstone Project is an archaeological research initiative led by Shumla in collaboration with Texas State University, funded by major national granting agencies (National Endowment for the Humanities and National Science Foundation). Field and lab work were completed in 2024, and the project is currently in analysis and write-up.

Its primary goal is deceptively direct: determine when and how ancient paintings in the Lower Pecos and adjacent Mexico were made—and what they were intended to communicate. But the subtext is larger. If Pueblo River Style murals are part of a coherent symbolic system – a possible set of ritual meanings then chronology also may answer questions about continuity or breaks in cultural transmission: how long a complex idea can persist, how faithfully it can be reproduced, and what kinds of social mechanisms may sustain it.

To build that chronology, Hearthstone relies on iconography, microscopic stratigraphy, and radiocarbon dating.

Hearthstone begins by identifying recurring motifs of the Pueblo River Style and mapping their distribution. Motifs include distinctive headdresses (rabbit-eared forms, antlers tipped with dots), ladders, crenellated arches (with “teeth”), stylized dart tips, “speech breath” (red dots or lines emanating from the mouths of figures, possibly representing the soul, ritual speech or song), and a particularly prevalent element researches have called a “power bundle,” a staff-like or dart motif extending from the arm of an anthropomorphic figure, frequently ending in an ovoid form.

This inventory of motifs functions as a sampling strategy. If you want to date a style – not merely a single painting – then your samples should be found across space, composition, and within motif variation.

Microscopic stratigraphy: reading the paint

(A) Zoomorphic, enigmatic, and anthropomorphic figures at 41VV1230.

The researchers also treated paint as if it was sediment. Where figures overlap, the order of layers can be determined through digital microscopy. Does red sit over black? Does yellow cut beneath red? Are two figures mutually interwoven, with one color above in one location, below in another, suggesting they were painted as parts of a single planned sequence rather than as additions made over time?

To organize these over/under relationships, researchers use Harris matrices, a tool originally developed for archaeological stratigraphy. In a dig, a Harris matrix maps which layers are older or younger; on a rock wall, it maps which paint applications occurred first. The result is a relative sequence of construction.

Across multiple Pecos River Style sites, the stratigraphy reveals something remarkable: a largely consistent color application sequence from darker to lighter hues—often black, then red, then yellow, and finally white. Deviations are rare. This appears to establish a rule in how the painters worked. Stratigraphy, however, is still relative. To place the Pueblo River Style in absolute time, Hearthstone needed dates.

Radiocarbon dating paint: the problem and the workaround

Dating pictographs is difficult because mineral pigments themselves – iron and manganese oxides, for example – contain no dateable carbon. The answer has to be found in the organic components of paint: binders, emulsifiers, or substances that the artists mixed with pigment to make it adhere.

Documenting the frangile artwork, Shumla Archaeological Research and Education Center.

But those organics are often present in tiny quantities. Traditional radiocarbon pretreatment and combustion can fail to extract enough carbon for measurement, or risk contaminating the sample. Hearthstone’s approach uses plasma oxidation[1] to extract organic carbon under conditions that reduce interference from carbon-bearing minerals in the substrate rock.

To increase confidence, the project also dates oxalate mineral accretions[2] that formed on the limestone walls, sometimes above and below paint layers. An underlying layer must be older than the paint above; an overlying layer must be younger. When the microstratigraphy shows that the older is below and the younger is above, it strengthens confidence in the order of paint dates, showing they aren’t just artifacts resulting from contamination.

Finally, to translate dozens of radiocarbon measurements into a coherent story, researchers use Bayesian chronological modeling (e.g. combining statistics radiocarbon dates with other clues such as stratigraphy and ceramic styles) to estimate start dates, end dates, and the duration of mural production, revealing continuity and potentially arguing that the Pecos River Style shows long standing traditions in Southwestern art.

From this combined evidence – iconographic selection, microscopic stratigraphy, direct paint dating, oxalate bracketing, and Bayesian modeling – comes Hearthstone’s central result:

Pecos River Style mural painting began between roughly 5,760 and 5,385 calibrated years ago and continued for more than 4,000 years, ended between 1,370 and 1,035 years before today.

This is not merely old. It means the same core style, motifs, and process endured across millennia of climatic change, demographic shifts, and technological transitions in hunting equipment. It implies the existence of social, ritual or pedagogical traditions that were faithfully reproduced over a very long time. This can be interpreted in different ways – as a continuous passing on of ideas across times of otherwise changing cultures, or as a response in each era to what passed before, a re-embracing and recreation of a valued tradition.

There is an added dimension. The data indicates that many large, complex murals were created within a relatively short span, perhaps even in single events, rather than slowly accumulated as a wall was revisited and repainted at random. To make a modern comparison, the walls behave less like a community bulletin board and more like a composed manuscript.

How motifs matter

To even begin to grasp the pictographs’ meaning, – to build a sort of vocabulary – you need to look at the way motifs recur, combine, and occupy positions in compositions.

Pecos River Style murals draw on a palette of earth colors – reds, oranges, yellows, blacks, whites – and generally apply them in a certain order. Anthropomorphic figures often carry paraphernalia (atlatls, darts, staffs), wear headdresses, and display adornments at wrists, elbows, waists, and hips. Deer, felines, birds, and snakes appear both as standalone beings and hybrids fused with human forms.

The repeated presence of motifs such as “speech breath” implies communication. “Power bundles” recur with such frequency that may represent an action or status rather than simply holding an object. What concept is robust enough to survive that long?

The cosmovision hypothesis

The researchers have proposed a possible cosmological framework – a way of ordering the relationships between humans, animals, supernatural beings and the landscape. Parallels between aspects of Pecos River Style imagery and cosmological concepts known from later Mesoamerican traditions have been noted for a long time. Interpretations differ in detail and confidence, but the broad claim is that Pecos River Style murals may represent an early expression of a foundational ideological “core” that later flourished in agricultural societies to the south.

Orthophotograph generated from an SfM (structure from motion) three-dimensional model of 41VV83. Credit Carolyn E. Boyd.

What Hearthstone adds is the argument that if Pecos River Style begins more than 5,000 years ago and persists for over 4,000 years, then parallels with later Mesoamerican cosmologies can no longer be dismissed as superficial resemblance or late diffusion alone. The murals become a serious candidate for an early, durable representation of cosmological principles crafted by mobile hunter-gatherers with sophisticated ritual and intellectual traditions. Yet the world is full of examples of deeply held, geographically centered artistic styles that are repeated across millennia – but in which each iteration of a similar motif holds a different meaning for the succeeding community – and which can embrace both techniques and a vocabulary of design. This periodic reinvention in which similar objects and motifs reappear after centuries is often found in ceramics and in textiles.[3]

Scholarship requires a careful distinction between what is known and what is speculation based on physical evidence. The Pecos River Style now has a far firmer chronology spanning millennia. Its murals show consistent, rule-bound paint sequencing; many large compositions were executed in short, intense episodes; motifs persist across time. The exact correspondence between Pecos River Style motifs and named myths from later historical sources is unknown, but may involve diffusion, deep shared ancestry of ideas, convergent symbolic solutions, or some combination of these factors.

However certain the conclusion, in the Lower Pecos, the past is not silent and with careful stewardship, it may remain readable -an ancient library whose walls still hold their lines.

About The Alexandra Project and The Hearthstone Project

The Alexandria Project (Lower Pecos Canyonlands of southwest Texas and northern Coahuila, Mexico) was conducted by Shumla researchers Charles W. Koenig, Amanda M. Castañeda, Victoria L. Roberts, Jerod L. Roberts, and Dr. Karen L. Steelman (all affiliated with Shumla Archaeological Research & Education Center, Comstock, Texas), working with Dr. Carolyn E. Boyd (affiliated with Shumla and the Department of Anthropology, Texas State University).

Its core published project write-up is “Around the Lower Pecos in 1,095 Days: The Alexandria Project,” published in American Indian Rock Art, Volume 45 (2019). The Hearthstone Project is a Texas State University–Shumla collaboration led by Dr. Carolyn E. Boyd and Dr. J. Phil Dering (both Department of Anthropology, Texas State University) with Dr. Karen L. Steelman (Science Director at Shumla; formerly a Full Professor of Chemistry at the University of Central Arkansas).

Published results include Boyd, Dering & Steelman (2023), “The Hearthstone Project: Applying Archaeological Science, Formal Art Analysis, and Indigenous Knowledge to Rock Art Research” (American Indian Rock Art, Volume 49), and Steelman, Boyd & Dering (Science Advances, Epub Nov 26, 2025), “Mapping the chronology of an ancient cosmovision…”, which reports direct radiocarbon dating and chronological modeling for Pecos River style murals across southwest Texas and northern Mexico.

Contact the Shumla Archaeological Research & Education Center

• Mailing Address: 102 Wonder World Dr., Unit 304-583, San Marcos, TX 78666
• Comstock Address: 28 Langtry – Unit 627, Comstock, TX 78837
• San Marcos Physical Address: 605 N Edward Gary St, Brazos Hall – First Floor, San Marcos, TX 78666
• Phone: 432-292-4848
• Email: info@shumla.org
• Tax ID/EIN: 74-2869788

[1] Plasma oxidation dates Pueblo River Style pictographs by using a low-pressure, energized oxygen plasma to convert organic components (like fats or plant matter used as binders) within the paint into carbon dioxide, which is then radiocarbon dated using Accelerator Mass Spectrometry to determine the age of the artwork.

[2] Oxalate mineral accretions (like calcium oxalate, whewellite) are crucial for dating Pueblo River Style pictographs.  They form layers over time, encapsulating the paint, allowing scientists to use radiocarbon dating (C¹⁴ dating) on the trapped organic carbon to determine the paint’s minimum age, providing a reliable timeline by dating layers above and below the paint.

[3] One striking example may be found in the recurrence of dominant motifs of the bronze, silver and gold ornaments of the sedentary agriculturalists of the Central Asian Bronze Age of 4000 years ago (roundels representing birds of prey, scorpions, rams etc.in abstracted, often reticulated forms), their reappearance in the textiles and ceramics of the urban silks and ceramics of the pre-Islamic cosmopolitan Sogdian trading cities of the 6^th-8^th centuries, and again dominating the motifs the embroideries of Muslim nomadic peoples of Turkic heritage in the 18^th-19^th C AD, who did not arrive on the steppe until thousands of years after the Bronze Age.