An argument that is often thrown against the evolutionary basis of life is the absence of likeliness that animals develop complex structures such as an eye. If evolution develops gradually, then how did eyes develop? What good is half an eye? Despite reasonable counterarguments that show that gradual steps of improvement can indeed lead to the improbable event of the creation of an eye, physical proof in the animal was still lacking. At the University of California in Santa Barbara scientists have proven what every evolutionist has already been proclaiming, by showing that there are animals with an intermediate form of vision. Not quite an eye, but certainly something that points in that direction.
Hydra
The Californian scientists studied a small sea animal called hydra. They possess poisonous tentacles which they use to catch their prey. In addition, researchers discovered that the poisonous cells built in these appendages are also used for tasting, and are sensitive to touch. A study in Santa Barbara revealed they contain one additional feature: light sensitivity.
Prey
By sensing light, the small hydra seem to be getting an idea of their surroundings. They do not possess eyes, however: they rely solemnly on the light sensitivity provided by the poisonous stinging cells. What the scientists found is that light actually inhibits the stinging potential, probably because hydra's prey is only active during the night. It is therefore as if light cues are telling the sea animals when to hunt. Additionally, it seems to be influencing its movements in the water.
Pathways
Even more remarkable, perhaps, is that hydra uses a mechanism to 'see' which is similar to what has been found in humans. A molecule called opsin is largely responsible for how hydra responds to light cues, and humans possess similar stuff to process light. Opsin aids in converting light signals into something the brain understands: electricity. However, hydra does not possess a brain, and you can hardly call their light sensitivity to be a form of vision. The sea animals do contain all the other necessary equipment for processing light, which is known as phototransduction.
Evolution
Light sensitivity of hydra is a prime example to counter the famous anti-evolution half-an-eye-argument. Even though humans and hydra are radically different, there are underlying similarities when it comes to absorbing light. It shows that even though it seems unlikely, having a rudimentary form of an eye, or light sensitivity, does not have to be useless. Even though the "what use is half an eye?" argument can easily be debunked by modern evolved thinking, of which Climbing Mount Improbably by Richard Dawkins is a prime example, having a real life example to add to it certainly helps. It reinforces the ideas about the evolution of modern life. Other recent examples include studies showing how multicellular life may have formed, the evolution of the essential process of photosynthesis, and clues to the birthplace of the first cells.
Hydra
The Californian scientists studied a small sea animal called hydra. They possess poisonous tentacles which they use to catch their prey. In addition, researchers discovered that the poisonous cells built in these appendages are also used for tasting, and are sensitive to touch. A study in Santa Barbara revealed they contain one additional feature: light sensitivity.Prey
By sensing light, the small hydra seem to be getting an idea of their surroundings. They do not possess eyes, however: they rely solemnly on the light sensitivity provided by the poisonous stinging cells. What the scientists found is that light actually inhibits the stinging potential, probably because hydra's prey is only active during the night. It is therefore as if light cues are telling the sea animals when to hunt. Additionally, it seems to be influencing its movements in the water.
Pathways
Even more remarkable, perhaps, is that hydra uses a mechanism to 'see' which is similar to what has been found in humans. A molecule called opsin is largely responsible for how hydra responds to light cues, and humans possess similar stuff to process light. Opsin aids in converting light signals into something the brain understands: electricity. However, hydra does not possess a brain, and you can hardly call their light sensitivity to be a form of vision. The sea animals do contain all the other necessary equipment for processing light, which is known as phototransduction.
Evolution
Light sensitivity of hydra is a prime example to counter the famous anti-evolution half-an-eye-argument. Even though humans and hydra are radically different, there are underlying similarities when it comes to absorbing light. It shows that even though it seems unlikely, having a rudimentary form of an eye, or light sensitivity, does not have to be useless. Even though the "what use is half an eye?" argument can easily be debunked by modern evolved thinking, of which Climbing Mount Improbably by Richard Dawkins is a prime example, having a real life example to add to it certainly helps. It reinforces the ideas about the evolution of modern life. Other recent examples include studies showing how multicellular life may have formed, the evolution of the essential process of photosynthesis, and clues to the birthplace of the first cells.
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