Rosa Rubicondior: Refuting Creationism - The Grand Canyon Is a Treasure Trove Of Cambrian Fossils - From 500 Million Years Before 'Creation Week'

Friday, 15 August 2025

Refuting Creationism - The Grand Canyon Is a Treasure Trove Of Cambrian Fossils - From 500 Million Years Before 'Creation Week'

View of the Grand Canyon from the Colorado River.

Jason Muhlbauer

Grand Canyon was a ‘Goldilocks zone’ for the evolution of early animals

One of the things about American creationism that many people in the rest of the world find endearing—if not more than a little irritating—is the ignorant parochialism that underpins so much of it. For example, it is part of the creationist narrative that the Grand Canyon is “proof” of the biblical flood because, so they assert, the layers were laid down during the flood and the canyon was then gouged out by the floodwaters running away. This also plays neatly into the biblical flat Earth idea, because they assume the floodwaters went somewhere—presumably over the edge—having been magically piled up for the best part of a year until the magic was removed.

And of course, it all happened in America, where the important things always happen and where anything that happens is important—when Jesus returns, it will be to America; America is the place God is preparing for Jesus’s return, and so on.

So the recent open-access paper in Science Advances by an international team of palaeontologists led by scientists from Cambridge University, UK, reporting that the Grand Canyon is a rich source of fossils from the Cambrian biota, will no doubt come as a shock to American creationists.

Grand Canyon Geology.

The Grand Canyon is essentially a 1.6-km-deep cross-section through nearly two billion years of Earth’s geological history, carved by erosion into the Colorado Plateau in northern Arizona. It’s both a geologist’s dream and a creationist’s nightmare. Here’s the overview:

The Setting

The Grand Canyon sits within the Colorado Plateau, a high, relatively flat region that was uplifted during the Laramide Orogeny (around 70–40 million years ago) when the Rocky Mountains were forming. That uplift was crucial—it raised the land high enough for rivers to gain the erosive power needed to cut deep canyons.

Rock Layers

The canyon walls expose a remarkably complete geological record. From bottom to top, the main sequences are:

Vishnu Basement Rocks (1.7–2.0 billion years old)
Dark, metamorphic schists and granites, formed from ancient volcanic island arcs and sediments, later buried and altered under intense heat and pressure.
Grand Canyon Supergroup (~1.2–0.8 billion years old)
Tilted sedimentary rocks—sandstones, shales, and limestones—deposited in ancient rift basins and later faulted and uplifted.
Paleozoic Strata (~541–250 million years old)
Flat-lying layers of marine and terrestrial sediments, recording changes from shallow seas to coastal deserts. Notable layers include:

Tapeats Sandstone (Cambrian) – beach and shallow marine deposits
Bright Angel Shale – muds from a continental shelf environment
Muav Limestone – deeper marine setting
Higher layers like the Redwall Limestone (Mississippian), Coconino Sandstone (Permian desert dunes), and Kaibab Limestone (Permian shallow sea).

These layers match sequences across much of North America, showing they were part of broad, regional environments—not a single catastrophic flood.

Canyon Formation

The Colorado River and its tributaries carved the Grand Canyon primarily in the last 5–6 million years, though there’s evidence that older river systems in the region may date back 17–70 million years. Key factors in its formation:

Uplift of the Colorado Plateau increased river gradients, accelerating erosion.
River capture events redirected ancient drainage systems into the modern Colorado River.
Base level drop as the river cut toward the Gulf of California (which formed as the Baja Peninsula separated from mainland Mexico) sped up downcutting.
Weathering and mass wasting widened the canyon via rockfalls, landslides, and debris flows.

Why It’s Not a Flood Deposit

If the Grand Canyon had formed from a single catastrophic flood, the rock layers would be chaotic, jumbled, and cross-cut—yet they’re neatly ordered, undisturbed except for ancient faults and folds that pre-date canyon formation. Fossils are arranged in evolutionary sequence from bottom to top, not mixed together. The erosional surfaces and soil horizons between layers show long intervals of time between deposits.

Geological Significance

Time capsule: Nearly two billion years of history exposed in one place.
Stratigraphic key: Correlates with rock sequences worldwide.
Erosional showcase: A textbook example of fluvial incision in an uplifted plateau.

The discovery not only dates the formation of that particular stratum to about 500 million years ago, but also adds another source of Cambrian fossils showing that the Cambrian biota was not the result of a single act of creation without ancestry, as creationists assert.

They deliberately misuse the term “Cambrian Explosion,” which in scientific usage refers to a period of accelerated diversification of life—lasting tens of millions of years—not to an instantaneous burst of creation. It’s rather like describing the Renaissance as if it had happened in a single afternoon. In reality, the Cambrian fauna emerged through a gradual evolutionary progression from the Ediacaran biota, during which the modern body plans of most major taxa were established in response to environmental pressures, particularly predation.

The research and its significance are explained in a University of Cambridge news release by Sarah Collins.

Grand Canyon was a ‘Goldilocks zone’ for the evolution of early animals
A treasure trove of exceptionally preserved early animals from more than half a billion years ago has been discovered in the Grand Canyon, one of the natural world’s most iconic sites.
The rich fossil discovery – the first such find in the Grand Canyon – includes tiny rock-scraping molluscs, filter-feeding crustaceans, spiky-toothed worms, and even fragments of the food they likely ate.

By dissolving the rocks these animals were fossilised in and examining them under high-powered microscopes, researchers led by the University of Cambridge were able to get a highly detailed picture of a unique period in the evolution of life on Earth.

The fossilised animals date from between 507 and 502 million years ago, during a period of rapid evolutionary development known as the Cambrian explosion, when most major animal groups first appear in the fossil record.

In some areas during this period, nutrient-rich waters powered an evolutionary arms race, with animals evolving a wide variety of exotic adaptations for food, movement or reproduction.

Sternal elements of crustaceans from the Cambrian period.

Most animal fossils from the Cambrian are of hard-shelled creatures, but, in a handful of locations around the world, such as Canada’s Burgess Shale formation and China’s Maotianshan Shales, conditions are such that softer body parts could be preserved before they decayed.

So far, however, fossils of non-skeletonised Cambrian animals had been known mostly from oxygen and resource-poor environments, unlikely to kickstart the most complex innovations that shaped early animal evolution.

Now, the Grand Canyon has revealed the first soft-bodied, or non-mineralised, Cambrian fossils from an evolutionary ‘Goldilocks zone’ that would have provided rich resources for the evolution of early animals to accelerate. The results are reported in the journal Science Advances.

These rare fossils give us a fuller picture of what life was like during the Cambrian period. By combining these fossils with traces of their burrowing, walking, and feeding – which are found all over the Grand Canyon – we’re able to piece together an entire ancient ecosystem.

Giovanni Mussini, first author
Department of Earth Sciences
University of Cambridge
Cambridge, UK.

Mussini and colleagues from the US located the fossils during a 2023 expedition along the Colorado River, which began carving the Grand Canyon in what is now Arizona between five and six million years ago.

Surprisingly, we haven’t had much of a Cambrian fossil record of this kind from the Grand Canyon before – there have been finds of things like trilobites and biomineralised fragments, but not much in the way of soft-bodied creatures. But the geology of the Grand Canyon, which contains lots of fine-grained and easily split mud rocks, suggested to us that it might be just the sort of place where we might be able to find some of these fossils.

Giovanni Mussini.

The researchers collected several samples and returned them to Cambridge. The fist-sized rocks were first dissolved in a solution of hydrofluoric acid, and the sediment was passed through multiple sieves, releasing thousands of tiny fossils within. None of the animals were preserved in their entirety, but many recognisable structures helped the researchers identify which groups the animals belonged to.

Further examination of the fossils revealed some of the most complex ways animals evolved during the Cambrian to capture and eat their food.

Credit: Joe Clevenger

These were cutting-edge ‘technologies’ for their time, integrating multiple anatomical parts into high-powered feeding systems.

Giovanni Mussini.

Many of these fossils are of crustaceans, likely belonging to the group that includes brine shrimp, recognisable by their molar teeth. These tiny creatures had hair-like extensions on triangular grooves around their mouths, and used their hairy limbs to sweep up passing food particles like a conveyer belt. Tiny grooves on their teeth could then grind up their food. The detail on the fossils is such that several plankton-like particles can be seen near the crustaceans’ mouths.

Other modern-looking animals from the Cambrian of the Grand Canyon include slug-like molluscs. These animals already had belts or chains of teeth not dissimilar to modern garden snails, which likely helped them scrape algae or bacteria from rocks.

An unusual new species

Artist's impression of Kraytdraco spectatus.
Credit: Rhydian Evans

The most unusual creature identified by the researchers is a new species of priapulids, also known as penis or cactus worms, which were widespread during the Cambrian but are nearly extinct today. The Grand Canyon priapulid had hundreds of complex branching teeth, which helped it sweep food particles into its extensible mouth. Due to the size of the fossil and its exotic rows of teeth, the researchers named this new animal Kraytdraco spectatus, after the krayt dragon, a fictional creature from the Star Wars universe.

We can see from these fossils that Cambrian animals had wide variety of feeding styles used to process their food, some which have modern counterparts, and some that are more exotic.

Giovanni Mussini.

Sections from the pharynx of Kraytdraco spectatus.
Credit: Mussini et al.

During the Cambrian, the Grand Canyon was much closer to the equator than it is today, and conditions were perfect for supporting a wide range of life. The depth of the oxygen-rich water, neither too deep or too shallow, allowed a balance between maximising nutrients or oxygen and reducing wave damage and exposure to UV radiation from the Sun.

This optimum environment made it a great place for evolutionary experimentation. Since food was abundant, animals could afford to take more evolutionary risks to stay ahead of the competition, accelerating the overall pace of evolution and driving the assembly of ecological innovations that still shape the modern biosphere.

Animals needed to keep ahead of the competition through complex, costly innovations, but the environment allowed them to do that. In a more resource-starved environment, animals can’t afford to make that sort of physiological investment. It’s got certain parallels with economics: invest and take risks in times of abundance; save and be conservative in times of scarcity. There’s a lot we can learn from tiny animals burrowing in the sea floor 500 million years ago.

Giovanni Mussini.

Publication:
Giovanni Mussini et al.
Evolutionary escalation in an exceptionally preserved Cambrian biota from the Grand Canyon (Arizona, USA). Science Advances (2025). DOI: 10.1126/sciadv.adv6383

Abstract
Exceptionally preserved fossil assemblages, or Konservat-Lagerstätten, open direct windows on non-biomineralized faunas that chronicle the Cambrian radiation of animal phyla. However, these assemblages do not typically capture the well-oxygenated, resource-rich environments sustaining most metazoan diversity in modern marine systems. We describe exceptionally preserved and articulated carbonaceous mesofossils from the middle Cambrian (~507 to 502 million years) Bright Angel Formation of the Grand Canyon (Arizona, USA). This biota preserves probable algal and cyanobacterial photosynthesizers together with a range of functionally sophisticated metazoan consumers: suspension-feeding crustaceans, substrate-scraping molluscs, and morphologically exotic priapulids with complex filament-bearing teeth, convergent on modern microphagous forms. The Grand Canyon’s extensive ichnofossil and sedimentological records show that these phylogenetically and functionally derived taxa occupied highly habitable shallow-marine environments, sustaining higher levels of benthic activity than broadly coeval macrofossil Konservat-Lagerstätten. These data suggest that evolutionary escalation in resource-rich Cambrian shelf settings was an important driver of the assembly of later Phanerozoic ecologies.

INTRODUCTION
The essential elements of Phanerozoic marine ecosystems became established in the Cambrian period (1). Burgess Shale–type (BST) macrofossil deposits, epitomized by the middle Cambrian [~505 million years (Ma) old] Burgess Shale of British Columbia, open a direct window on the non-biomineralized organisms that dominated Cambrian communities, typically preserving them as carbonaceous compressions (2–5). “BST biotas” or “BST faunas” denote both this distinctive taphonomic window and a loose set of taxonomically overlapping assemblages dominated by stem-group relatives of living phyla (2, 5). These biotas contain few examples of the modern taxonomic classes and derived lifestyles (e.g., substrate miners, zooplanktonic suspension feeders, and a multitiered epifauna) that typify later Paleozoic communities (6) despite emerging evidence for protracted Cambrian origins of some of these habits [e.g., (7–9)].

However, exceptional preservation of BST-macrofossil biotas typically corresponds to similarly “exceptional” environmental conditions, with limited degradation and reworking of carcasses by bioturbators, scavengers, and decomposers (3, 4). Most early Cambrian BST-macrofossil biotas, which sample slope to prodelta environments (e.g., the Chengjiang, Emu Bay Shale, and Sirius Passet Lagerstätten), show evidence for dysoxic to anoxic burial conditions (10–13). Middle Cambrian counterparts record similarly oxygen-limited offshore settings: Among them are the outer detrital deposits of the Burgess Shale (4, 5); the Wheeler, Marjum, and Weeks biotas of Utah (14); and the Kaili biota of China (4, 15–17). The Spence Shale of Utah and Idaho records a broader inner shelf to offshore gradient (18); nonetheless, its bottom waters were at least intermittently dysaerobic (19–21). Organically preserved, submillimeter-scale small carbonaceous fossils (SCFs) (3) have further extended the range of BST metazoans into shallow epicratonic (3) to episodically subaerial (22) settings. However, studies on these (typically disarticulated) body fossils often lack detailed interpretation of associated trace fossils and environmental indicators (3, 23–26)—or sample habitats colonized only by the most ecophysiologically tolerant metazoans (22). The result of this combination of taphonomic biases and unequal study efforts across paleoenvironments is an overrepresentation of ecologically “marginal” settings by Cambrian biotas preserving non-biomineralized taxa.

This biased paleoenvironmental coverage affects our ability to test macroevolutionary hypotheses about the assembly of Phanerozoic ecologies. In particular, in stable, resource-rich environments hosting structured trophic networks, the main agents of selection tend to be other organisms rather than extrinsic abiotic factors (27, 28). Therefore, such settings may be more conducive to evolutionary escalation (28–31): the directional, open-ended ratcheting of adaptive innovations against biotic “enemies” (28–32), ranging from trophic competitors to predators and pathogens. Its result is a long-term elevation of biological “performance standards” (28) in resource acquisition and maintenance, driving the assembly of increasingly elaborate means of defense, offense, and food or energy capture. In turn, these innovations can unlock and inject a wider share of resources into the broader ecosystem, promoting further escalation (28, 29, 33). In its self-amplifying, open-ended nature, escalation differs from both “court jester” scenarios, which posit extrinsic abiotic forcings as first-order drivers of macroevolution, and alternative zero-sum coevolutionary models postulating a fixed share of available resources, such as the Red Queen hypothesis 29). Unlike zero-sum models, the escalation hypothesis predicts that the elevation of biotic performance standards does not generally lead to the simultaneous extinction of less competitive taxa; instead, it relegates them in step-wise fashion to progressively more resource-poor, physiologically marginal settings as ecological baselines are ratcheted up by derived competitors (28, 30, 31).

Constructing and maintaining complex adaptations for resource acquisition and retention requires outlays of energy; therefore, escalation is considered more likely to be initiated under evolutionarily permissive (28) conditions, whereby intense biotic competition takes place in arenas of plentiful and accessible nutrients, oxygen, and energy sources. These settings can sustain open-ended antagonistic coevolution and provide sufficient resources to bypass physiological trade-offs, promoting the buildup of increasingly elaborate, high-investment adaptive traits (30). However, the macroevolutionary impact of escalation remains incompletely understood, not least because of the relative paucity of non-biomineralized faunas [compare with (32)] and discontinuous paleoenvironmental coverage (29) of the fossil record. To date, Cambrian escalation has been tested almost exclusively through the lens of the shelly fossil record rather than the more patchily preserved, but more broadly representative record of non-biomineralizing organisms (32, 34). If escalation had a pervasive influence on the trajectory of early Phanerozoic evolution, Cambrian non-mineralized faunas under more permissive conditions may be predicted to show both adaptations for higher performance standards of resource acquisition (28) and greater taxonomic and functional overlap with later Paleozoic successors, compared to biotas from coeval marginal habitats (4, 22).

Here, we describe a middle Cambrian biota under comparatively “permissive” conditions: an oxygenated, fully marine shelf setting marked by abundant traces of metazoan activity relative to broadly coeval macrofossil Lagerstätten. We report exceptionally preserved priapulid, crustacean, and molluscan SCFs from the lower to middle Bright Angel Formation (BAF) (~505 Ma) (35, 36) in Grand Canyon National Park (Arizona, USA), representing a nearshore-offshore bathymetric gradient (Fig. 1, A to C) hosting well-aerated, extensively bioturbated normal marine shelf environments (36–39) . Microstructural data from the Bright Angel SCFs complement the Grand Canyon’s biomineralized and trace fossil records to reveal an unusually wide range of coexisting derived taxa and sophisticated feeding adaptations, in a deposit no more than ~3 Ma younger than the Burgess Shale.

Fig. 1. Paleogeography, paleoenvironment, and lithology of the BAF.
(A) Reconstruction showing paleoenvironmental map of western North America in the Middle to Late Cambrian (~505 to 495 Ma), showing locations of major exceptionally preserved biotas (14, 18, 22–25, 51, 60); Deadwood Formation localities, coming from later time intervals, are not from terrestrial settings. Source map 2023 Colorado Plateau Geosystems Inc. (B) Detail of boxed area in (A), broadly corresponding to present-day Arizona. Dotted lines denote transgressive progression of shorelines (520 to 500 Ma), from (40); colored dots correspond to fossil locations 1 to 4 as shown in (C). (C) Paleoenvironmental reconstruction of the Grand Canyon area at the time of deposition of the Bright Angel biota (~505 Ma), showing positions of the present-day Colorado river and major faults for orientation. Red dots indicate locations of the SCF biota described herein; blue previously described assemblages from the Red Canyon and Sumner Butte localities recovered through standard palynological processing (37). Legend on the right summarizes major organically preserved fossils recorded at each locality. (D) Wheeler diagram of the Tonto Group after (36), showing Cambrian Series, stages, trilobite biozones, and main lithologies as indicated by legend on the right [which is specific to (D)]. Localities shown in fig. S11, situated near studied ichnofossil sections, are marked by name on the horizontal axis. Vertical axis is based on relative thickness of zones; question marks indicate that basal clastics lack biostratigraphic and geochronologic control beyond maximum depositional ages 36). Disconformities identified by missing trilobite bizones. FMD, Frenchman Mountain Dolostone; GW, Grand Wash fault; Ss, sandstone; Peach.-Neph., Peachella iddingsi to Nephrolenellus multinodus; Eok., Eokochaspis nodosa; Ame., Amecephalus arrojosensis; Pol., Poliella denticulata; Mex., Mexicella mexicana; Gloss., Glossopleura walcotti; Pro., Proehmaniella; Elra., Elrathiella; Ehm., Ehmaniella; Bolas., Bolaspidella; Ced., Cedaria; Crep., Crepicephalus.

Giovanni Mussini et al.
Evolutionary escalation in an exceptionally preserved Cambrian biota from the Grand Canyon (Arizona, USA). Science Advances (2025). DOI: 10.1126/sciadv.adv6383

Copyright: © 2025 The authors.
Published by the American Association for the Advancement of Science. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The discovery of Cambrian fossils in the Grand Canyon is more than just another exciting find—it’s a fossilised time-stamp from half a billion years ago, locked into the rock long before the first land plants, mammals, or humans ever existed. For science, it’s yet another piece of the vast, coherent jigsaw of Earth’s history, fitting perfectly into the evolutionary timeline that links the Ediacaran world to the modern biosphere. For creationism—if its adherents dare to look—it’s an inconvenient truth in stone: the rocks are older than their entire worldview, the fossils record evolution, not sudden magic, and the Grand Canyon is a monument to deep time, not to a year-long flood that never happened.

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