Rosa Rubicondior: Creationism Refuted - How The Fossil Record Tracks Climate Change

The climate in Catalonia was much rainier 10 million years ago - Universitat Autònoma de Barcelona - UAB Barcelona

A paper published a few days ago in the Journal of Mammalian Evolution describes how the climate in Catalonia was much wetter 10 million years ago than it is today, with rainfall roughly twice the present rate, and how this was reflected in the evolution of mammals in the region. The study was conducted by palaeontologists at the Institut Català de Paleontologia Miquel Crusafont (ICP-CERCA), in association with colleagues from the Universitat Autònoma de Barcelona (UAB).

This must be deeply frustrating for creationists because, no matter how much they ignore the evidence, misrepresent it, or shout abuse at scientists, the evidence stubbornly refuses to support creationism and invariably supports evolution over deep time on an ancient Earth. The findings presented in this paper are, of course, no exception.

Scientists have previously established a close link between rainfall and the composition of mammalian communities, with wetter conditions favouring insectivores. Increased rainfall promotes the development of forests, which in turn provide abundant niches for insects and other invertebrates—the primary food source of insectivorous mammals. This relationship between small mammals and climate was first studied in detail by Jan van Dam, an associate researcher at the ICP. Van Dam developed equations that allow both average annual rainfall and its seasonal distribution to be estimated from fossil assemblages of small mammals.

Building on that earlier work, the present study analyses the abundant fossil record of small mammals to reconstruct populations that changed dynamically through time in response to shifting climatic conditions—exactly as predicted by the Theory of Evolution. There is, unsurprisingly, no evidence of spontaneous creation of species, nor of a global biological reset caused by a genocidal flood a few thousand years ago.

Small mammals as climate proxies. Small mammals are among the most sensitive indicators of past climate change, particularly rainfall and seasonality. Because of their short lifespans, rapid reproductive cycles, and narrow ecological tolerances, shifts in climate are reflected quickly in the composition of their communities.

In wetter conditions, forested habitats expand, supporting abundant insect life. This favours insectivorous small mammals, while drier, more open environments tend to favour herbivorous and granivorous species adapted to grasslands and scrub. As a result, the relative abundance of different dietary groups within fossil assemblages provides a powerful signal of past environmental conditions.

Research at the Institut Català de Paleontologia Miquel Crusafont has shown that these patterns are sufficiently robust to allow quantitative estimates of palaeorainfall. By analysing fossil communities of rodents, insectivores, and other small mammals, researchers can reconstruct not only average annual precipitation but also how rainfall was distributed seasonally.

This approach was developed in detail by Jan van Dam and colleagues, and has since been applied to multiple regions and time periods. When combined with independent geological and botanical evidence, small mammal assemblages provide a high-resolution record of climate change spanning millions of years.

Crucially, these reconstructions show gradual, directional change through deep time, tracking well-established climatic shifts rather than any sudden, global ecological reset—exactly what evolutionary theory predicts, and exactly what creationist models fail to explain.

In short, the small-mammal fossil record of Miocene Catalonia records a wet-to-dry climatic transition unfolding over millions of years, not the chaotic aftermath of a recent, world-destroying flood.

The study is explained in a press release from UAB.

The climate in Catalonia was much rainier 10 million years ago
A study by the Institut Català de Paleontologia Miquel Crusafont (ICP-CERCA) with the involvement of the UAB indicates that between 12.5 and 9 million years ago, in the Vallès-Penedès basin, rainfall was twice as high as it is today, and the climate was subtropical. The research has reconstructed the precipitation and climatic conditions of the past from fossils of small mammals found throughout the area.
Every 2 February in the town of Punxsutawney (US), all eyes are on a meteorologist rodent: Phil the groundhog. According to tradition, if he sees his shadow when emerging from his burrow and retreats, winter will last six more weeks; if not, spring will arrive soon. This ceremony gained fame thanks to the movie Groundhog Day (1993), in which Bill Murray is doomed to relive the same day endlessly. But can rodents really predict the weather? Perhaps not exactly, yet they do have a close relationship with climate, which can help us reconstruct past climates.

Rodents, along with other small mammals such as insectivores (shrews, hedgehogs, and moles) and lagomorphs (rabbits and pikas), are among the most diverse and abundant mammals in today’s terrestrial ecosystems, and they were also in the past. In fact, large numbers of their fossilized remains are recovered in paleontological sites, allowing for statistical analyses. It has been observed that in wetter climates there are more arboreal and insectivorous species, as higher rainfall favours denser forests, rich in invertebrates. This link between small mammals and climate was first studied in detail by Jan van Dam, an associate researcher at the ICP. Van Dam developed equations to estimate both the average annual rainfall and how it was distributed across seasons, by looking at fossil small mammal communities.

Rainfall in the Vallès-Penedès basin was twice today’s level

Now, an ICP team at UAB has applied these methods to discover what the climate may have been like during the Miocene in the Vallès-Penedès Basin (the depression between the Pre-Coastal Range and the Coastal Range), between 12.5 and 9 million years ago. This record is exceptional: it includes hundreds of precisely dated sites from which more than 20,000 small mammal fossils have been recovered. The results indicate that over this interval of more than 2 million years, annual precipitation remained stable and quite consistently exceeded 1,000 mm (roughly doubling today’s levels), with little seasonality and without a clear summer drought.

Since the mean temperature was also higher, around 17–18°C, the climate would have been subtropical and more humid than the Mediterranean climate. It is difficult to find an exact analogue today, but it may have resembled the climate of eastern coastal Asia, such as southeastern China or southern Japan. These areas lie at the edge of the subtropics and are covered by dense, humid forests mixing deciduous and evergreen trees, such as cinnamon or certain types of bay trees.

In Catalonia, during the Miocene, various primates lived in this environment, including hominids and pliopithecoids, which went extinct around 9 million years ago, possibly due to climatic changes. Pliopithecoids were small arboreal primates, whereas hominids are the family that includes —besides humans— chimpanzees, gorillas, and orangutans, which today mainly inhabit tropical rainforests. During the Miocene, they were widespread across Europe and Asia and certainly lived in habitats that would be too harsh for modern species.

For the ICP researcher and professor of the UAB Department of Geology Isaac Casanovas-Vilar “it is possible that these small mammals became extinct in the Vallès-Penedès basin so that they ‘malvise’ for survival in the wetter areas of subtropical forests, generally near small lakes, where most fossils are found. If so, even a small change, such as slightly lower temperatures or a more severe drought, could have led to their definitive extinction. For now, this remains a hypothesis, but new studies are expected to provide answers. Perhaps the ancestors of Phil the groundhog have not yet had their final say.

Publication:
Casanovas-Vilar, I., van Dam, J., Angelone, C. et al.
Micromammal-based paleoprecipitation estimates for the late Middle and early Late Miocene record of the Vallès-Penedès Basin (Catalonia): Implications for primate habitats.
J Mammal Evol 32(48) (2025). https://doi.org/10.1007/s10914-025-09788-x

Abstract
The densely sampled and well dated late Aragonian to Vallesian succession (late Middle to early Late Miocene, 12.5–9.0 Ma) of the Vallès‑Penedès Basin (VP) in Catalonia has yielded one of the richest primate records in Eurasia, including hominoids and pliopithecoids. Here we present high‑resolution mean annual precipitation (MAP) estimates derived from the ecological structure of small mammal assemblages to infer the paleoclimate and habitats associated with these primates. Our approach uses the relative abundance of arboreal and insectivore taxa as a paleoprecipitation proxy, producing robust results when sampling is sufficient. MAP values generally cluster around ~1,000 mm with low seasonality. Combined with mean annual temperature (~17–18 °C), this suggests a transitional climate between humid subtropical and Mediterranean regimes. These conditions would have supported diverse environments—subtropical evergreen broadleaf and mixed mesophytic forests interspersed with drier woodlands—consistent with the arboreal locomotor adaptations and inferred dietary preferences of VP primates. We find no evidence for distinct habitat partitioning between hominoids and pliopithecoids, nor for significantly more humid environments during primate‑bearing intervals. Climatic parameters remained relatively stable even through major faunal turnovers such as the Vallesian Crisis (~9.7 Ma), indicating that local extinction of hominoids and other taxa was likely not driven by abrupt climate change, but rather by longer‑term climatic deterioration or subtle environmental perturbations that affected the marginal habitats to which these species may have been restricted.

Fig. 1

Simplified geological map of the Vallès-Penedès Basin showing major vertebrate sites dated to 12.5–9.0 Ma (late Aragonian–Vallesian). Locality acronyms are as follows: ACM, Abocador de Can Mata (including Ecoparc de Can Mata; although the symbol used stands for the late Aragonian the series ranges from the late Aragonian to the early Vallesian); CB, Castell de Barberà; CCN20, Creu de Conill 20; CL, Can Llobateres; CM3, Can Mata 3; CMI, Can Missert; CP, Can Poncic; CRU, Can Cruset; CV, Ceràmiques Viladecavalls; LTR1, La Tarumba 1; PO, Polinyà; S, Santiga; SQ, Sant Quirze; TF, Torrent de les Febulines; TNA, Trinxera Nord Autopista; TSA, Trinxera Sud Autopista. Modified from Casanovas-Vilar et al. (2016b: fig. 1)

Casanovas-Vilar, I., van Dam, J., Angelone, C. et al.
Micromammal-based paleoprecipitation estimates for the late Middle and early Late Miocene record of the Vallès-Penedès Basin (Catalonia): Implications for primate habitats.
J Mammal Evol 32(48) (2025). https://doi.org/10.1007/s10914-025-09788-x

Copyright: © 2026 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Far from abandoning the Theory of Evolution, modern science continues to deepen and refine it, embedding the relationship between organisms and their environments ever more firmly at its core. What once began as the qualitative observation that species adapt to changing conditions has matured into a quantitative framework capable of generating testable predictions—so reliable, in fact, that evolutionary change itself can now be used as a tool to reconstruct past climates.

The Catalonian mammal record illustrates this with particular clarity. Changes in rainfall, vegetation, and habitat structure are written directly into the fossil record as predictable shifts in community composition, tracked over millions of years. Evolution is not an abstract idea imposed on the data; it is the pattern that emerges from the data, independently and repeatedly, wherever sufficiently detailed records exist.

This is why creationist claims that evolution is “in crisis” or “abandoned” ring so hollow. A scientific theory in retreat does not underpin entire research programmes, nor does it allow palaeontologists to estimate rainfall patterns ten million years in the past with measurable confidence. Evolutionary theory does exactly that—quietly, routinely, and with increasing precision.

The irony, of course, is that while creationism must constantly reinvent itself to evade the evidence, evolutionary biology has become so well established that it now serves as a practical instrument for understanding Earth’s history. The organisms themselves are the record keepers, and they testify—without ambiguity—to change over deep time on a very old planet.

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