The ancestor of humans was a 600 million year old one-eyed creature like Cyclops, know how we got a pair of eyes?

New Delhi. A small worm-like creature that lived in the ocean millions of years ago and had only one eye on its head may be the ancestor of today's humans and every vertebrate animal. A new research by Lund University (Sweden) and University of Sussex (UK) has completely changed our understanding of eye development. Researchers say that this ancient one-eyed creature is the real reason for our pair of eyes and its trace is still present in our brain in the form of pineal gland.

What was this Cyclops-like ancestor like?

According to research, about 600 million years ago this creature used to stay at one place in the sea and fill its stomach by filtering plankton from the surrounding water. Earlier during its evolution, it had two eyes or groups of cells that could detect light, but these pairs of eyes were of no particular use in a life that remained stationary in one place. The result was that these eyes gradually disappeared over the course of several generations. However, a cluster of light-sensing cells remained in the middle of the head, which later transformed into a 'median eye'.

What was the function of this one eye?

This middle eye could not form any clear images, but it definitely helped the creature to understand the difference between day and night and to decide which direction was up. Both these things were very important to survive in the sea.

Then how did the pair of eyes return?

Millions of years later, when this creature's descendants became active and swimming again, they again needed better vision to find food, avoid predators, and navigate. Researchers believe that evolution then reused parts of the same old central eye and gradually evolved into the pair of image-forming eyes that we see today.

Why are our eyes different from those of insects?

Professor Dan-E Nilsson, lead scientist of the research, says, now we finally understand why the eyes of vertebrate animals are so different from the eyes of insects and squid. The retina of our eyes is formed from the brain, while the eyes of insects and squid develop from the skin of the head. The retina is a thin layer of tissue in the back of the eye, which detects light and converts it into electrical signals and sends it to the brain.

The unique journey of eye development

Scientists have come to this conclusion after a large comparison of light sensing cells in different groups of animals. The team investigated where these cells appear in the body, how they work, and how they connect to other tissues and nerves. All the evidence points towards the fact that the eyes of vertebrate animals were formed in this unique sequence. Professor Nilsson says, for the first time, we now also understand the origins of the neural circuits that analyze images in our retina.

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