New study sheds light on how and when vision evolved

Oct 29, 2012

The study, which used computer modelling to provide a detailed picture of how and when opsins evolved, sheds light on the origin of sight in animals, including humans.

The of vision remain hotly debated, partly due to inconsistent reports of among the earliest opsin-possessing animals.

Dr Davide Pisani of Bristol's School of 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 (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 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."

These results are reported in the PNAS journal article 'Metazoan opsin evolution reveals a simple route to animal vision'.

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JVK
2 / 5 (4) Oct 29, 2012
Were it not for the required chemical ecology of adaptive evolution, vision could not have evolved. A blind "opsin ancestor" could no more meet its nutrient chemical requirement for survival than it could find a mate to ensure species survival -- unless a fully functional olfactory/pheromonal processing system was already established. The fact that human nutrient chemical acquisition and mate choice are equally dependent on the evolutionarily conserved gonadotropin-releasing hormone (GnRH) suggests olfactory primacy across at least a 700 million year evolutionary continuum of all species, and places visual input in a lesser role in the context of adaptive evolution -- except where evolutionary theorists are involved in perturbations of known biological facts. For example: olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans. http://dx.doi.org...i0.17338