For millions of years, mammals have evolved in the shadow of dinosaurs, shaped by a hostile environment where discretion was a question of survival. Unlike prehistoric birds in bright colors, these first mammals displayed a uniform and dark coat, a long line remained elusive for scientists. A recent study has just lifted the veil on the color of the first mammals, revealing a common chromatic heritage which could be the key to their adaptation to a world dominated by predators.
To achieve these conclusions, the researchers used advanced imaging techniques. They compared the fossilized melanosomes, responsible for the production of melanin, to those of 116 current species. This analysis confirmed that these first mammals shared a dark hue, strengthening the hypothesis of a nightlife. As Popular Science indicates, these results question the idea that the diversity of colors in mammals dates back to their origins.
An adaptation linked to their nightlife
The first mammals lived in the shadow of dinosaurs. Small size, mainly nocturnal, they adopted a survival strategy allowing them to escape the dominant predators of the mesozoic. Their uniform color played a key role in this lifestyle: a dark coat offered them optimal camouflage in the dark, thus reducing the risks of being identified.
Researchers at the University of Ghent, including Matthew Shawkey, discovered that the color of the peeling of ancient mammals was not random. She played a key role in their survival, influencing their thermoregulation and adaptation to hostile environments. This uniformity also suggests a constraint imposed by dinosaurs. Their presence would have limited the diversification of mammals, not only in terms of morphology, but also biological characteristics such as color.
However, this theory is debated. Luke Weaver, a paleontologist at the University of Michigan, stresses that some recent studies offer another perspective. Mammals of late Cretaceous already had advanced social behavior and greater ecological diversity than we thought. If many were hiding, others also hunted small dinosaurs. Their role was therefore not limited to that of discreet prey.
The evolution of the color of the mammals after the dinosaurs
The domination of dinosaurs maintained the first mammals in a narrow evolutionary niche, limiting their physical and behavioral diversity. But after the massive extinction of the end of the Cretaceous, about 66 million years ago, these animals experienced a spectacular expansion. One of the most striking aspects of this evolution concerns the diversification of their appearance, especially in terms of coat.
The extinction of dinosaurs has upset the ecosystems. According to The University of Chicago Press Journal, it has opened new ecological niches. Mammals then explored various habitats and adopted new behaviors. It was during this period that their colors evolved. The first spotted and striped patterns appeared, improving their camouflage. Today, these variations also play an essential role in the communication and attraction of partners.
The study published in Science shows that the evolution of the coat could be linked to changes in the structure of melanosomes. In the past, mammals had uniform melanosomes in size and shape. Today, these structures vary a lot, creating a diversity of colors and patterns. A student from Matthew Shawkey's laboratory seeks to establish a precise chronology of this transformation. It also tries to identify the environmental factors that have influenced this process.
These discoveries recall the importance of the conservation of fossils and museums, which allow access to formerly unimaginable data. As Steve Brusatte, paleontologist at the University of Edinburgh points out, the technological advances today offer the possibility of reconstructing in detail the appearance and way of life of the missing species. Thanks to this research, it becomes possible to retrace with increasing precision the evolutionary history of mammals, from their modest beginnings to their brilliant current diversity.
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