Bold hues of red, orange, yellow, blue, and purple assist plants and animals in communication and survival. Vivid orange dart frogs signal toxicity to predators, while various birds use colorful plumage to attract mates. Flowers display a spectrum of colors to entice birds and bees for pollination.
The evolution of coloration has occurred gradually; colorful fruit-like seeds emerged around 300 million years ago, vibrant flowering plants appeared 100 million years later, and animals, such as cockroaches and butterflies, developed bolder pigmentation approximately 70 million years after that. However, recent research indicates that the ability of animals to perceive multiple colors predates the existence of those colors.
A study published in Biological Reviews indicates that color vision originated about 500 million years ago, existing in a landscape dominated by browns, grays, and muted colors. Bright colors across vertebrates and arthropods did not emerge until around 400 million years later. John J. Wiens, co-author of the study and professor of ecology and evolutionary biology at the University of Arizona, stated, 'There was this long lag time between the explosion of color and the origins of color vision.'
Researchers utilized a phylogenetic tree to trace the evolution of coloration, mapping genetic relationships and analyzing fossils with preserved pigments. Wiens and co-author Zachary Emberts, an integrative biologist at Oklahoma State University, further examined genes encoding protein receptors in animals' visual systems to establish when species could perceive color. Their findings revealed that hundreds of millions of years separated the development of color vision from conspicuous coloration.
The evolutionary significance of color vision raises questions about its early utility. The study suggests that color vision may have aided early species in distinguishing between living green leaves and dead brown ones, as well as identifying predators against their backgrounds. Wiens noted that in marine environments, where vertebrates first evolved, color vision was crucial for navigating light-filtered hues underwater.
While the study's findings are substantial, Innes C. Cuthill, a professor of behavioral ecology at the University of Bristol, remarked that it does not encompass the entirety of color vision. The research focused on trichromatic color vision, similar to that of humans, and did not address ultraviolet (UV) vision, which many insects possess. Cuthill pointed out, 'The colors that we see aren't what matters to most animals.'
Wiens acknowledged that many aspects of color vision remain unexplained, stating, 'There's a very long fuse before this explosion of color occurred, and we don't really know why.'