The world has become vibrant. When and how did animals actually develop their bright colors? (Photo)

The Earth's history spans billions of years, during which our planet has become home to an incredible number of species. The natural world is adorned with a myriad of vibrant colors, but this beauty has not evolved for our enjoyment — in fact, bright colors are often advantageous for animals: they help attract mates or deter predators, as noted by Science Alert.

Yet, the origin of these attention-grabbing colors remains a mystery. Scientists are still unsure which came first: the bright colors in the wild or the ability of animals to see them.

In a new study, American researchers shed light on what is known as the "explosion of animal color signals" over the past 100 million years. According to co-author Zachary Emberts, an integrative biologist from Oklahoma State University, their work aimed to determine when bright coloration evolved and what its purpose was.

During the study, Emberts and lead author John Vins, an evolutionary ecologist from the University of Arizona, analyzed literature on color signals used by plants and animals.

The researchers believe that noticeable colors in plants likely evolved under selective pressure from animals, given the reliance of color signals on vision. Plants utilize two main types of color signals: colorful fruits attract fruit-eating animals to act as seed dispersers, while bright flowers attract pollinators.

At the same time, animals use color in various ways, including camouflage and heat regulation; however, brighter colors typically convey one of two messages: "check me out" or "leave me alone." Some species also use vibrant colors to attract potential mates, while others employ brightness as a strategy known as aposematism, where conspicuous colors advertise toxicity, persistence, or other qualities of the animal to deter intruders.

Vins and Emberts concluded that color vision in animals emerged first — it developed more than 100 million years before plants began producing colorful flowers and fruits. It is believed to have appeared around 500 million years ago, likely occurring simultaneously in ancient arthropods and vertebrates.

It is thought that the first vertebrates with color vision likely lived in marine environments, but it is not entirely clear where and how it evolved in arthropods. It is also uncertain what evolutionary advantages color vision provided back then, prior to the emergence of color signaling in plants or animals.

Scientists suggest that color perception may have helped animals visually explore objects, nesting sites, and food sources. Even before the advent of bright fruits and flowers, color vision could have been beneficial for distinguishing between objects like green and brown leaves.

At the same time, the plant world took some time to benefit from this development. Researchers believe that the first signaling color fruits appeared around 300 million years ago, while eye-catching colors in flowers emerged only about 200 million years ago. Animals began using color signals even later, starting with aposematic warnings.

The findings of the new study suggest that warning colors emerged around 150 million years ago, followed by sexual color signals, which debuted only around 100 million years ago — approximately 400 million years after the emergence of color vision.

It is important to note that the factors that triggered the explosion of color signals remain a mystery, but scientists have identified three groups of animals that likely fueled this trend:

• ray-finned fish contributed in marine habitats;
• birds and lizards led the process on land.

This research helps map the evolutionary history of color vision and signaling in animals, but there is still much to learn about these phenomena, including what drives variations in color vision among different animals.