Svo augað er vel hannað eftir allt saman

Richard Dawkins og fleiri þróunarsinnar hafa notað þau rök að augað sé ekki hannað vegna þess að það er hönnunargalli í auganu. Hérna útskýrir Dawkins þessi rök sín.

 

 

 

Við höfum haft margar ástæður til að ætla að þessi rök Dawkins séu röng en á þessu ári þá bættist við önnur rannsókn á auganu sem varpar enn frekari ljósi á hvort að augað sé vel hannað eða ekki.

Þeir segja t.d. þetta:

Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision
Vision starts with the absorption of light by the retinal photoreceptors -- cones and rods. However, due to the 'inverted' structure of the retina, the incident light must propagate through reflecting and scattering cellular layers before reaching the photoreceptors. It has been recently suggested that Müller cells function as optical fibres in the retina, transferring light illuminating the retinal surface onto the cone photoreceptors. Here we show that Müller cells are wavelength-dependent wave-guides, concentrating the green-red part of the visible spectrum onto cones and allowing the blue-purple part to leak onto nearby rods. This phenomenon is observed in the isolated retina and explained by a computational model, for the guinea pig and the human parafoveal retina. Therefore, light propagation by Müller cells through the retina can be considered as an integral part of the first step in the visual process, increasing photon absorption by cones while minimally affecting rod-mediated vision.
(Amichai M. Labin, Shadi K. Safuri, Erez N. Ribak, and Ido Perlman, "Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision," Nature Communications, DOI: 10.1038/ncomms5319 (July 8, 2014).)

...

Having the photoreceptors at the back of the retina is not a design constraint, it is a design feature. The idea that the vertebrate eye, like a traditional front-illuminated camera, might have been improved somehow if it had only been able to orient its wiring behind the photoreceptor layer, like a cephalopod, is folly. Indeed in simply engineered systems, like CMOS or CCD image sensors, a back-illuminated design manufactured by flipping the silicon wafer and thinning it so that light hits the photocathode without having to navigate the wiring layer can improve photon capture across a wide wavelength band. But real eyes are much more crafty than that.
A case in point are the Müller glia cells that span the thickness of the retina. These high refractive index cells spread an absorptive canopy across the retinal surface and then shepherd photons through a low-scattering cytoplasm to separate receivers, much like coins through a change sorting machine. A new paper in Nature Communications describes how these wavelength-dependent wave-guides can shuttle green-red light to cones while passing the blue-purples to adjacent rods. The idea that these Müller cells act as living fiber optic cables has been floated previously. It has even been convincingly demonstrated using a dual beam laser trap. In THIS case (THIS, like in Java programming meaning the paper just brought up) the authors couched this feat as mere image transfer, with the goal just being to bring light in with minimal distortion. 

 

Sem sagt, hönnunar eiginleiki sem gerir sjónina enn skýrari. Gaman að vita hvort að þetta dugi til að Dawkins viðurkenni að hann hafði rangt fyrir sér.

 

Meira hérna: http://www.evolutionnews.org/2014/12/6_of_our_top_te092241.html 

Athugasemdir

[Gunnlaugur Hólm Sigurðsson, 2.1.2015 kl. 00:25]

Er þá Guð að gera grín að okkur? Er augað bara sköpun sem þarf svo að leyðrétta með Leisir eða gleraugum ?