When you throw dinosaurs into the mix, sometimes you find that a rule simply isn’t.
A new study led by scientists at the University of Alaska Fairbanks and the University of Reading calls into question Bergmann’s rule, an 1800s-era scientific principle stating that animals in high-latitude, cooler climates tend to be larger than close relatives living in warmer climates.
The fossil record shows otherwise.
“Our study shows that the evolution of diverse body sizes in dinosaurs and mammals cannot be reduced to simply being a function of latitude or temperature,” said Lauren Wilson, a UAF graduate student and a lead author of a paper published in the journal Nature Communications. “We found that Bergmann’s rule is only applicable to a subset of homeothermic animals (those that maintain stable body temperatures), and only when you consider temperature, ignoring all other climatic variables. This suggests that Bergmann’s ‘rule’ is really the exception rather than the rule.”
Examination of Bergmann’s Rule in Dinosaurs and Modern Species
The study started as a simple question Wilson discussed with her undergraduate advisor: Does Bergmann’s rule apply to dinosaurs?
After evaluating hundreds of data points gleaned from the fossil record, the answer seemed a solid “no.”
The dataset included the northernmost dinosaurs known to scientists, those in Alaska’s Prince Creek Formation. They experienced freezing temperatures and snowfall. Despite this, the researchers found no notable increase in body size for any of the Arctic dinosaurs.
Next the researchers tried the same evaluation with modern mammals and birds, the descendants of prehistoric mammals and dinosaurs. The results were largely the same: Latitude was not a predictor of body size in modern bird and mammal species. There was a small relationship between the body size of modern birds and temperature, but the same was not the case for prehistoric birds.
The researchers say the study is a good example of how scientists can and should use the fossil record to test current-day scientific rules and hypotheses.
“The fossil record provides a window into completely different ecosystems and climate conditions, allowing us to assess the applicability of these ecological rules in a whole new way,” said Jacob Gardner, a postdoctoral researcher at the University of Reading and the other lead author of the paper.
Scientific rules should apply to fossil organisms in the same way they do modern organisms, said Pat Druckenmiller, director of the University of Alaska Museum of the North and one of the co-authors of the paper.
“You can’t understand modern ecosystems if you ignore their evolutionary roots,” he said. “You have to look to the past to understand how things became what they are today.”
Reference: “Global latitudinal gradients and the evolution of body size in dinosaurs and mammals” by Lauren N. Wilson, Jacob D. Gardner, John P. Wilson, Alex Farnsworth, Zackary R. Perry, Patrick S. Druckenmiller, Gregory M. Erickson and Chris L. Organ, 5 April 2024, Nature Communications.
DOI: 10.1038/s41467-024-46843-2
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3 Comments
I wonder how migration would affect the rule (either altitudinal or latitudinal). For example, studying birds that live half of the year in Arctic Summer and half the year in equatorial winter might not be helpful. Likewise for goats that seek lower altitudes during the winter.
According to Pat Druckenmiller, vertebrate paleontologist and director of the University of Alaska Museum of the North, “You have to look to the past to understand how things became what they are today.” Examining valuable clues from the past, such as studying interesting fossils, can provide present-day researchers with a mammoth amount of useful data helpful in establishing and substantiating evolutionary theories.
We might look at the time period for the deposition of the Prince Creek Formation fossils. I am writing a paper on the Cretaceous – Paleocene extinction that suggests that it was caused by a massive asteroid strike that created the entire Gulf of Mexico, and pushed a massive wave of earth, mud, water and organic matter northwest across the entire continent, to settle in what is now Alaska.
If there are temperate plant fragments mixed in with all the animal fragments (whole plants do not migrate) this would confirm this conjecture.
Please contact me at the email below to review the prepublication paper, entitled “Planetary Forensic Ballistics” with far more evidence for this hypothesis.
I am a scientist/designer with 6 years on the faculty at one of the world’s most renowned undergraduate design schools.