The discovery that a group of organisms has, contrary to “Cope’s Rule,” undergone a steady reduction in body size over the past 200 million years is a useful reminder of how science works — and why religion so often falters.
A cornerstone of the scientific method is its willingness to acknowledge error. Real intellectual strength lies not in clinging to discredited beliefs as though doing so were a test of character, but in facing up to mistakes, learning from them, and changing one’s mind. That is how knowledge advances.
Religion, by contrast, remains shackled to the dogmas of its ancient founders. To alter those fundamental beliefs is, in effect, to abandon the religion itself. This is why, while science has sent probes into deep space and placed human beings on the Moon, faith — despite lofty claims of being able to “move mountains” — has yet to lift so much as a feather a millimetre off the ground.
The new finding was just reported in the journal Palaeontology by Associate Professor MA Junye of the Nanjing Institute of Geology and Paleontology at the Chinese Academy of Sciences (NIGPAS) and collaborators. They found that Berenicea, a genus of cyclostome bryozoans, has experienced a continuous reduction in zooid size over the past 200 million years. This runs counter to “Cope’s Rule,” which describes a tendency for body size to increase during the evolution of many lineages.
Cope’s Rule was formulated by the American palaeontologist Edward Drinker Cope (1840–1897). There are, of course, well-known exceptions — such as the “island effect,” where animals isolated on small islands often evolve into miniature versions of their mainland relatives — but these are localised adaptations to particular environments. Cope’s Rule, by contrast, applies to long-term, broad-scale evolutionary trends.
Background^ Berenicea and the Bryozoans.The discovery and its significance are explained in a news release from the Chinese Academy of Sciences.Taxonomic position
- Kingdom: Animalia
- Phylum: Bryozoa (also known as Ectoprocta)
- Class: Stenolaemata
- Order: Cyclostomatida
- Genus: Berenicea
Bryozoans are colonial, filter-feeding invertebrates that first appeared in the early Ordovician, more than 470 million years ago. Each colony is made up of numerous tiny individuals called zooids, which live in connected tubes or chambers. Although individually microscopic, bryozoan colonies can grow into intricate branching, encrusting, or fan-shaped structures.
Berenicea is an extinct genus of cyclostome bryozoans, a group that was especially abundant in the Mesozoic seas. Unlike the more familiar moss animals of modern marine environments, Berenicea colonies typically formed thin, encrusting sheets on shells, rocks, or other hard substrates, creating a delicate but extensive living mat.
Feeding and ecology
Cyclostome bryozoans like Berenicea were suspension feeders, filtering plankton and organic particles from the water using a crown of ciliated tentacles known as a lophophore. They played a significant role in shallow marine ecosystems, both as filter feeders and as part of reef and hard-ground communities.
Evolutionary significance
Bryozoans are part of the Lophotrochozoa, a major branch of the animal kingdom that also includes molluscs and annelids. Cyclostomes represent one of the oldest and most conservative bryozoan lineages, with a fossil record stretching back to the Ordovician.
The long-term reduction in zooid size observed in Berenicea over some 200 million years provides a rare example of sustained miniaturisation, offering valuable insight into macroevolutionary trends that run counter to broad generalisations like Cope's rule.
New Study Reveals Berenicea's Zooid Size Reduction Over 200 Million Years Contradicts Cope's Rule
Body size evolution has long been a core topic in paleontological research. "Cope's Rule" describes the tendency for body size to increase during the evolution of many lineages. However, a new study focusing on bryozoans, a group of modular organisms, has uncovered a different evolutionary pattern.
Associate Prof. MA Junye from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), and his collaborators found that Berenicea, a genus of cyclostome bryozoans, has experienced a continuous reduction in zooid size over the past 200 million years. This trend runs directly counter to Cope's Rule.
The findings were recently published in the journal Palaeontology.
By analyzing 200 Berenicea morphotype samples dating from the Late Triassic to the present, the research team documented a significant decline in maximum zooid width over time. This pattern stands in sharp contrast to the long-term stability of zooid size in cheilostome bryozoans, challenging the prior hypothesis that the two groups followed similar body size evolution trajectories.
To identify the driving factors, the researchers used multiple time-series models to test potential influences, including changes in oxygen levels, the origination rate of cheilostome bryozoans, and their proportion within ecological communities. Results showed that while oxygen levels and zooid size exhibit a statistical correlation, no causal relationship exists. Similarly, the rise of cheilostomes as dominant competitors for space did not directly trigger Berenicea's zooid size reduction.
Additionally, the study ruled out the potential impact of paleolatitude (and associated temperature) changes on zooid size, further emphasizing the intrinsic nature of this reduction trend. Model analysis revealed that the size reduction process was not constant: it underwent two major phase shifts, around 165–160 million years ago and 78 million years ago.
This study marks the first systematic documentation of zooid size reduction in cyclostome bryozoans over macroevolutionary timescales. The team suggests the trend may be linked to optimized metabolic efficiency or shifts in feeding niches, rather than being a direct response to external environmental pressures or interspecific competition.
Cyclostome bryozoans of the Berenicea morphotype.(Image by NIGPAS)
Publication:
AbstractFar from being a rigid orthodoxy, science thrives on the constant testing and questioning of its own ideas. “Rules” such as Cope's rule are not immutable laws handed down from on high but generalisations that stand only so long as they continue to fit the evidence. When new data emerge that don’t conform to expectations, science doesn’t silence the finding — it publishes it, examines it, and, if necessary, revises its understanding.
Body size evolution is a focus of palaeobiological interest, but few studies have examined long-term changes in the size of the modular zooids of colonial animals. Here we investigate changes in zooid size from the Late Triassic to the present-day among encrusting cyclostome bryozoans of a common morphotype attributed informally to ‘Berenicea’. We begin with the naïve hypothesis that cyclostome bryozoans should demonstrate size evolution similar to cheilostome bryozoans, which have maintained a constant mean zooid size. Unexpectedly, a striking pattern of decreasing zooid size through time was found in ‘Berenicea’. We then hypothesized that decreasing levels of oxygen could make smaller zooid sizes more optimal because of their greater surface area/volume; cyclostome zooid size might be tracking a changing adaptive landscape over 200 million years. Despite some evidence for a statistical correlation between ‘Berenicea’ zooid size and oxygen, there is no hint of any causal relationship between them when formal timeseries analysis tools, based on linear stochastic differential equations, are applied. Furthermore, neither origination rates of cheilostomes, known to be superior spatial competitors, nor assemblage-level increases in cheilostome representation, are associated with ‘Berenicea’ zooid size changes. However, there is some support for a switch in the tempo of cyclostome zooid size change at c. 165 to 160 Ma and then again at c. 78 Ma.
Ma, J., Liow, L.H. and Taylor, P.D. (2025)
Zooid size reduction in cyclostome bryozoans from the Late Triassic to the present-day. Palaeontology, 68: e70027. https://doi.org/10.1111/pala.70027
© 2025 John Wiley & Sons, Inc .
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.
This is precisely what we see with this study of Berenicea bryozoans: a well-supported observation that challenges a long-standing evolutionary trend. Rather than being rejected for contradicting a “consensus,” it was peer-reviewed and published precisely *because* it contributes something new to our understanding of how life evolves. That’s how scientific knowledge grows — not through blind conformity, but through evidence and reasoned debate.
This also exposes the creationist misrepresentation of peer review. It is not a mechanism for enforcing dogma but a filter to ensure that claims are supported by robust evidence and sound reasoning. When those standards are met, even results that overturn established ideas are welcomed.
In short, the scientific enterprise advances by correcting itself; dogma resists change. This willingness to follow the evidence, wherever it leads, is what distinguishes science from faith — and why science continues to deepen our understanding of the natural world, while religion remains rooted in the unchanging beliefs of its past.
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