Why did life evolve to be so colorful? Research is starting to give us some answers

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Picture a primordial Earth: a world of muted browns, grays and greens. Fast forward to today, and Earth teems with a kaleidoscope of colors. From the stunning feathers of male peacocks to the vivid blooms of flowers, the story of how Earth became colorful is one of evolution. But how and why did this explosion of color happen? Recent research is giving us clues into this part of Earth's narrative.

The journey towards a colorful world began with the evolution of vision, which initially developed to distinguish light from dark over 600 million years ago. This ability probably arose in early organisms, like single-celled bacteria, enabling them to detect changes in their environment, such as the direction of sunlight. Over time, more sophisticated visual systems evolved and allowed organisms to perceive a broader spectrum of light.

For example, trichromatic vision—the ability to detect three distinct wavelengths such as red, green and blue—originated approximately 500–550 million years ago. This coincided with the "Cambrian explosion" (about 541 million years ago), which marked a rapid diversification of life, including the development of advanced sensory systems like vision.

The first animals with trichromatic vision were arthropods (a group of invertebrates that includes insects, spiders and crustaceans). Trichromatic vision emerged 420–500 million years ago in vertebrates. This adaptation helped ancient animals to navigate their environments and detect predators or prey in ways that monochromatic vision could not.

Fossil evidence from trilobites, extinct marine arthropods that roamed the seas over 500 million years ago, suggests they had compound eyes. This means eyes with multiple small lenses, each capturing a fraction of the visual field, which combine to form a mosaic image. These eyes could detect multiple wavelengths, providing an evolutionary advantage in dim marine environments by enhancing the animal's visibility and motion detection.

The stage was set: organisms could see a colorful world before they became colorful themselves.

The first burst of conspicuous color came from plants. Early plants began producing colorful fruits and flowers, such as red, yellow, orange, blue and purple, to attract animals to help plants with seed dispersal and pollination.

Analytical models based on present-day plant variation suggest that colorful fruits, which appeared roughly 300–377 million years ago, co-evolved with seed-dispersing animals, such as early relatives of mammals. Flowers and their pollinators emerged later, around 140–250 million years ago. These innovations marked a turning point in Earth's palette.

The rise of flowering plants (angiosperms) in the Cretaceous period, over 100 million years ago, brought an explosion of color, as flowers evolved brighter and more vibrant hues than seeds to attract pollinators like bees, butterflies and birds.

Conspicuous coloration in animals emerged less than 140 million years ago. Before, animals were mostly muted browns and grays. This timeline suggests that color evolution was not inevitable, shaped instead by ecological and evolutionary factors, which could have led to different outcomes under different circumstances.

Vibrant colors often evolved as a kind of signaling to attract mates, deter predators, or establish dominance. Sexual selection probably played a strong role in driving these changes.

Dinosaurs provide some of the most striking evidence of early animal coloration. Fossilized melanosomes (pigment-containing cell structures called organelles) in feathered dinosaurs like Anchiornis reveal a vivid red plumage.

These feathers probably served display purposes, signaling fitness to mates or intimidating rivals. Similarly, the fossilized scales of a green and black ten million-year-old snake fossil suggest early use of color for signaling or camouflage.

The evolution of color is not always straightforward. Take poison frogs, for instance. These small amphibians display striking hues of blue, yellow, or red, not to attract mates but to warn predators of their toxicity, a phenomenon known as aposematism.

But some of their close relatives, equally toxic, blend into their environments. So why evolve bright warning signals when camouflage could also deter predators? The answer lies in the local predator community and the cost of producing color. In regions where predators learn to associate vibrant colors with toxicity, conspicuous coloration is an effective survival strategy. In other contexts, blending in may work.

Unlike many mammals, which have dichromatic vision and see fewer colors, most primates including humans have trichromatic vision, enabling us to perceive a broader range of hues, including reds. This probably helped our ancestors locate fruit in forests and likely played a role in social signaling. We see flowers differently from pollinators like bees, which can detect ultraviolet patterns invisible to us, highlighting how color is tailored to a species' ecological needs.

A world still changing

Earth's palette isn't static. Climate change, habitat loss, and human influence are altering the selective pressures on coloration, potentially reshaping the visual landscape of the future. For example, some fish species exposed to polluted waters are losing their vibrant colors, as toxins disrupt pigment production or visual communication.

As we look to the past, the story of Earth's colors is one of gradual transformation punctuated by bursts of innovation. From the ancient seas where trilobites first saw the world in color to the dazzling displays of modern birds and flowers, life on Earth has been painting its canvas for over half a billion years.

What will the next chapter of this vibrant story hold?

This article is republished from THE CONVERSATION under a Creative Commons license. Read the original article.

Author:  Jonathan Goldenberg