A new study shakes environmental theories

When you add dinosaurs to the mix, sometimes you find that the norm is simply not the case.

A new study by scientists at the University of Alaska Fairbanks and the University of Reading questions Bergmann's rule, a 19th-century scientific principle that states that animals living at high latitudes and cold climates tend to be larger than their 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 a mere function of latitude or temperature,” said Lauren Wilson, a UAF graduate student and lead author of a paper published in the journal. Nature Communications. “We found that Bergmann's rule applies only to a subset of endothermic animals (those that maintain stable body temperatures), and only when temperature is taken into account, ignoring all other climatic variables. This suggests that the 'rule' Bergman is really the exception rather than the rule.”

An examination of Bergmann's rule in dinosaurs and modern species

The study began as a simple question that Wilson discussed with her college advisor: Does Bergmann's rule apply to dinosaurs?

After evaluating hundreds of data points from the fossil record, the answer seemed like a solid “no.”

The data set included the northernmost dinosaurs known to scientists, those found in Alaska's Prince Creek Formation. They experienced freezing temperatures and snowfall. Despite this, researchers did not find any significant increase in body size for any of the Arctic dinosaurs.

Next, the researchers tried to make the same assessment with modern mammals and birds, which are descendants of prehistoric mammals and dinosaurs. The results were largely the same: latitude was not a predictor of body size in modern birds and mammals Classify. There was a small relationship between the body size of modern birds and temperature, but this was not the case for prehistoric birds.

The researchers say the study is a good example of how scientists can use the fossil record to test current scientific rules and hypotheses.

“The fossil record provides a window into completely different ecosystems and climate conditions, allowing us to evaluate the applicability of these ecological rules in a completely new way,” said Jacob Gardner, a postdoctoral researcher at the University of Reading and the other lead author of the book. the paper.

Scientific rules should apply to fossil organisms in the same way they apply to modern organisms, said Pat Druckenmiller, director of the University of Alaska's Museum of the North and one of the paper's co-authors.

“You can't understand modern ecosystems if you ignore their evolutionary roots,” he said. “You have to look back to understand how things became the way they are today.”

Reference: “Global latitudinal gradients and the evolution of body size in dinosaurs and mammals” by Lauren N. Wilson, and Jacob D. Gardner, and John B. Wilson, Alex Farnsworth, Zachary R. Perry, and Patrick S. and Chris L. Organ, April 5, 2024, Nature Communications.
doi: 10.1038/s41467-024-46843-2