Remember when researchers used dinosaur fossils to challenge a long-believed scientific rule?

Our knowledge of the past is everchanging. Not everything we think that we know today will be true in the future, and a good example of this comes from a recent study that challenged a long-held scientific belief about how animals evolved on our planet.

Science has long held that the evolution of animal body sizes was influenced by the climate that they inhabited but this long-held scientific theory might be completely wrong according to researchers.

Biologists have believed that animal body sizes correlated to their external environment ever since German researcher Carl Bergmann noticed something intriguing about many of the animals that he was studying in the mid-1800s. 

Bergmann realized that animals in cold climates could be expected to have larger bodies compared to those in warmer climates according to Newsweek. This bizarre observation became known as Bergmann's Rule. 

Photo Credit: Wiki Commons By Unknown Author, University Archives Rostock, Public Domain

Bergmann’s Rule has been an accepted scientific principle for about one hundred and fifty years but recent research from the University of Alaska Fairbanks and the University of Reading has challenged the principle.

“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 lead author of the study. 

Wilson explained that Bergmann's Rule only applied to a subset of homeothermic animals, which means those animals that can maintain their body temperature, in a statement published by the University of Alaska Fairbanks. 

However, that wasn’t the study’s only finding. Bergmann's Rule not only just applies to an animal that can control its body temperature, but the researchers noted that Bergmann's Rule only works if other key conditions are ignored. 

Bergmann's Rule only applies when all other climatic variables are ignored according to Wilson, which she said meant that Bergmann's Rule was “really the exception rather than the rule.” But how was this discovery made?

Wilson and her colleagues looked through fossil records to investigate whether or not there was a correlation between body size and climate in prehistoric times. They found little evidence that Bergmann's Rule applied. 

The information analyzed included data from the most northern dinosaurs known to us at this time, those discovered in Alaska’s Prince Creek Formation. However, the fossil records did not conform to Bergmann’s Rule. 

Photo Credit: Wiki Commons By Artwork by Masato Hattori, CC BY 4.0

Dinosaurs from the Prince Creek Formation dataset would have had to endure “freezing temperatures and snowfalls” according to the researchers, but they found little evidence for an increase in body size for any Arctic dinosaur. 

The researchers began their analysis with a simple question. They wanted to figure out if Bergmann's Rule applied to dinosaurs, and their answer was a resounding no. There are a lot of reasons why this is important. 

Primarily, the researchers noted that their work showed why fossil records were still a great way to test modern scientific theories and hypotheses—which is critical when trying to understand both our past and present. 

“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, another author of the study. 

Director of the University of Alaska Museum of the North and study co-author Pat Druckenmiller explained that our scientific rules should apply to fossil organisms as well as modern-day organisms. 

Photo Credit: Facebook @uafairbanks

“You can’t understand modern ecosystems if you ignore their evolutionary roots,” Druckenmiller said. “You have to look to the past to understand how things became what they are today.”