When did the ability to see evolve? According to eye-opening new research, the first light-sensitive proteins that made vision possible first appeared some 700 million years ago, about 160 million years earlier than previously known. The researchers used computer models to resolve the long-contested origin of animal vision.


The study, conducted by researchers from the National University of Ireland Maynooth and the University of Bristol, was published Oct. 29 in the journal Proceedings of the National Academy of Sciences.


So where did vision come from? The researchers examined opsins, light-sensitive proteins that exist in the photoreceptors of all beings that can see, even those that lack eyes but still react to stimuli.


Specifically, the researchers looked at simple invertebrates called Placozoa, which possess the simplest structures of any multicellular animals. As the researchers write in the abstract to their paper, "We found that the Placozoa have opsins, and that the opsins share a common ancestor with the melatonin receptors." After performing a computational analysis of genomic information from all relevant animal lineages, they developed a timeline that revealed a common opsin ancestor that they say appeared 700 million years ago. This opsin evolved over a span they calculate at 11 million years until it had the critical ability to detect light.


In a prepared release from the University of Bristol, co-author Davide Pisani said this discovery proves that sight first evolved for all life at the same time.


"The great relevance of our study is that we traced the earliest origin of vision and we found that it originated only once in animals," he said. "This is an astonishing discovery because it implies that our study uncovered, in consequence, how and when vision evolved in humans."


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