Nature is loud with colour: warning reds, courtship blues, camouflage greens. But which came first, the signals or the eyes capable of seeing them? Reconstructing half a billion years of evolutionary history, researchers have tried to settle the order of events, and their answer complicates the assumption that colour vision drove the evolution of colour.
The analysis traces the duplication and divergence of opsin genes, the molecular building blocks of light detection, alongside the appearance of pigments and structural colours used for signalling. The two did not advance in lockstep. In some lineages, colour vision appeared first, giving animals the ability to discriminate hues before there was much to discriminate between. In others, elaborate colours evolved and were later matched by better vision.
The finding fits a broader pattern in evolutionary biology, in which sensory systems and the signals they detect coevolve in unpredictable ways. It also helps explain why colour serves such different purposes in different groups, from mate attraction to species recognition to simple camouflage.
