Vision evolved 700 million years ago: scientists

The exact point in time when ancient species developed the first rudimentary ability to see light has been hotly contested.

Scientific opinion was divided over which sponges or jellyfish types species first possessed opsins, a group of light-sensitive protein-coupled receptors in photoreceptor cells of the retina, the Daily Mail reported.

Bristol's School of Earth Sciences and colleagues looked at a newly sequenced group of sponges named Oscarella carmela, and the jellyfish type Cnidarians, a group of animals thought to have possessed the world's earliest eyes.

The study used computer modelling to provide a detailed picture of how and when opsins evolved.

Dr Davide Pisani performed a computational analysis to test every hypothesis of opsin evolution proposed to date.

The analysis incorporated available genomic information from all relevant animal lineages to develop 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.

"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," Pisani said.

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

The study was published in the journal Proceedings of the National Academy of Sciences.