Animals were seeing stuff a lot earlier than previously thought, a new study suggests.

When exactly the ability to see evolved in animals has been hotly contested among boffins, but researchers from Bristol and Maynooth universities reckon a group of marine animals first "saw" the light 700 million years ago.

Using computer modelling, the scientists figured out how and when opsins evolved in a group of marine animals including jellyfish, which are considered to have had the world's earliest eyes. Opsins are the protein receptors which confer the ability to sense light in all animals that have had sight throughout time.

The program used data from every hypothesis of opsin evolution to date as well as all the available genomic information from a recently discovered group of sponges called Oscarella carmela and Cnidarians, or jellyfish.

The team, from Bristol Uni's School of Earth Sciences and National University of Ireland Maynooth, now reckon that an opsin ancestor common to all the group started showing up 700 million years ago. That opsin was 'blind' but over the next 11 million years it evolved genetically to allow it 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," Dr Davide Pisani of Bristol said. "This is an astonishing discovery because it implies that our study uncovered, in consequence, how and when vision evolved in humans."

The study was published in the Proceedings of the National Academy of Sciences (PNAS). ®