On both page and screen, we’re used to seeing dinosaurs and prehistoric birds as vibrant creatures exhibiting unique and diverse patterns in color and texture. But what about the mammals roaming the earth alongside them?

In a new study published in Science, an international team of scientists has discovered that early mammals had dark and dull fur, no matter the species. This uniform fur coloring had evolutionary advantages and allowed mammals to avoid becoming prey to their more colorful neighbors. 

A Mesozoic Mammal Find

Thanks to a comparative analysis of fossilized mammals, researchers can now confirm that Mesozoic mammals, who lived about 150 million years ago, uniformly exhibited dark fur. The color of their fur has also given insights into how early mammals evolved and how they interacted with other species and their changing environment.

The color of an animal’s fur is quite complex and can tell us things about how they behave. For these early mammals, their dark fur suggests that they lived a mainly nocturnal lifestyle. It’s likely that their fur looked similar to that of modern nocturnal mammals, such as moles, mice, rats, and nocturnal bats. 

Unlike other modern mammals, however, these early ancestors’ fur was dull and plain and didn’t exhibit any patterns, like stripes and spots, that we see on many mammals today. 

Read More: Mammals Diversified Much More Rapidly 66 Million Years Ago

A Breakthrough in Color

Much of this evolutionary and ecological data about early mammals has remained unknown due to the scarcity of information about the pigmentation and coloration of extinct mammal coats. For this study, the team used a similar technique to the one used to reconstruct dinosaur coloration.

Fossilized melanosomes are key to this reconstructive technique. Melanosomes are the specialized subunits within a cell that are responsible for pigmentation. Luckily, these can be easily located and tested for mammals using well-preserved fur specimens, of which there are plenty from the Mesozoic era.

Using living mammals first, the researchers analyzed melanosomes from 116 specimens. With these analyses, they were able to then create a predictive model for reconstructing fur color that was then applied to six fossilized mammals. 

It was through this predictive model that they discovered the distinct evolutionary pattern of dark fur in early mammals.

The Advantages of Dark Fur

The absence of patterns and shiny coats likely assisted these mammals with camouflage and allowed them to blend in more easily with their surroundings. Additionally, it’s probable that dark fur assisted in the mammals’ ability to regulate their internal temperature and added to their mechanical strength.

Interestingly, these findings reveal that, although early mammals significantly differ biologically and ecologically, their color system remained mostly unchanged.

That was until the Cretaceous-Paleogene extinction event. Once their dinosaur competition was wiped out, mammals rapidly diversified. This diversification allowed mammals to develop new fur colors and patterns that were better suited to their newly broadened environment and to become the spotted and striped mammals we know and love today.

Read More: Established Science Is Wrong About Mammalian Evolution, Study Claims

Article Sources

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As the marketing coordinator at Discover Magazine, Stephanie Edwards interacts with readers across Discover’s social media channels and writes digital content. Offline, she is a contract lecturer in English & Cultural Studies at Lakehead University, teaching courses on everything from professional communication to Taylor Swift, and received her graduate degrees in the same department from McMaster University. You can find more of her science writing in Lab Manager and her short fiction in anthologies and literary magazine across the horror genre.