Date Published: 29 October 2012

The origins of vision: Opsins (light-sensitive proteins) may have evolved earlier than previously thought

A new study has shed light on how and when vision evolved:
Opsins, light-sensitive proteins that are essential for vision (eyesight), may have evolved earlier and undergone fewer genetic changes than previously thought.

This is the outcome of a recent study by experts at the National University of Ireland (Maynooth) and the Bristol University, England. The study used computer modelling to provide detailed information about how and when opsins evolved. This helps explain the origin of sight (vision) in animals, including humans (human evolution). The evolutionary origins of vision are still vigorously debated, partly due to inconsistent reports of phylogenetic relationships, that is the relationships between different groups of organisms such as populations or species, among the earliest opsin-possessing animals.

Dr Davide Pisani of Bristol University's Schools of Biological Sciences and Earth Sciences and colleagues at NUI Maynooth performed a computational analysis to test every hypothesis of opsin evolution proposed to date. The analysis incorporated all available genomic information from all relevant animal lineages, including a newly sequenced group of sponges (Oscarella carmela) and the Cnidarians, a group of animals thought to have possessed the world's earliest eyes.

Using this information, the researchers developed a timeline with an opsin ancestor common to all groups appearing some 700 million years ago. This opsin was considered 'blind' yet underwent key genetic changes over the span of 11 million years that conveyed the ability to detect light.

Dr Pisani said:

"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. This is an astonishing discovery because it implies that our study uncovered, in consequence, how and when vision evolved in humans."

Ref. to Paper
'Metazoan opsin evolution reveals a simple route to animal vision' by Roberto Fueda, Sinead C. Hamilton, James O. McInerney, and Davide Pisani in PNAS.

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