3 ms·

See for example this: http://www.futurity.org/top-stories/skins-eye-like-receptors-see-uv-light/ http://www.futurity.org/top-stories/skins-eye-like-receptors...

See for example this: http://www.futurity.org/top-stories/skins-eye-like-receptors-see-uv-light/ http://www.futurity.org/top-stories/skins-eye-like-receptors... "Skin is able to detect ultraviolet light by using a receptor previously thought to only exist in the eye." Having light sensitive cells inside your head (in other places than eyes) obviously sounds ridiculous if you believe in intelligent design. However if you think about evolution and how it works, I would say there is pretty good chance all our cells do not have just the functions they absolutely need to have.

Tichy 15y ago
You seem to assume that skin cells don't need to detect ultraviolet light.
zerostar07 15y ago
Skin cells are not part of the nervous system, they apparently use rhodopsin just to regulate melanin. You can make any part of the brain photosensitive by injecting Channelrhodopsin viral vectors, that's an exciting recent experimental area called optogenetics.
scarmig 15y ago
It's fairly difficult to pinpoint something that humans have that couldn't have been placed there intelligently. Evolution drives organisms, if at all possible, to co-opt anything that develops because of structural constraints. Most of the time it is possible. This class of traits is something that Steven J Gould named as evolutionary spandrels. So in practice, I would expect the ultraviolet receptors in the skin to have at least one meaningful function. The fact that exposing people to ultraviolet light changes their hormonal balance would tend to suggest this as well. They're definitely doing something. As a separate argument, a creationist could also provide some information theoretic arguments for why some cells have pointless features. Unnecessary complexity in a biological organism, like in any other computer program, is a dangerous risk. As risk management, we might want to handle that danger by accepting a harmless redundancy and not building an additional subsystem that chaotically interacts with all our other subsystems.

Tichy 15y ago

You seem to assume that skin cells don't need to detect ultraviolet light.

zerostar07 15y ago

Skin cells are not part of the nervous system, they apparently use rhodopsin just to regulate melanin. You can make any part of the brain photosensitive by injecting Channelrhodopsin viral vectors, that's an exciting recent experimental area called optogenetics.

scarmig 15y ago

It's fairly difficult to pinpoint something that humans have that couldn't have been placed there intelligently. Evolution drives organisms, if at all possible, to co-opt anything that develops because of structural constraints. Most of the time it is possible. This class of traits is something that Steven J Gould named as evolutionary spandrels. So in practice, I would expect the ultraviolet receptors in the skin to have at least one meaningful function. The fact that exposing people to ultraviolet light changes their hormonal balance would tend to suggest this as well. They're definitely doing something. As a separate argument, a creationist could also provide some information theoretic arguments for why some cells have pointless features. Unnecessary complexity in a biological organism, like in any other computer program, is a dangerous risk. As risk management, we might want to handle that danger by accepting a harmless redundancy and not building an additional subsystem that chaotically interacts with all our other subsystems.