Evidence for Former Star?

[cigarshaped]

The basis for Colour Television is the human eye's photopic response. The sensitivity of retina cells (cones) to 3 bands of wavelengths gives us the RGB colour system. What is never discussed is why the eye's response does NOT match the sun's spectral output. You will notice that our cones have an extremely high Green response, whereas Blue is particularly low sensitivity.
Below you should see a basic Human Eye photopic response:

Photopic curve (lowres)

Photopic1.gif (2.73 KiB) Viewed 49804 times

and the Sun's Radiation Spectrum

Solar Spectrum (lowres)

Solar_Spectrum_a.png (36.76 KiB) Viewed 49804 times

(Higher Res)

There are several learned sites which refer to the original measurement problems eg this by Jame T. Fulton

The eye's senstivity to low light levels is also intersting as it shifts to blue/ UV wavelengths "At this very low light level, sensitivity to blue, violet, and ultraviolet is increased, but sensitivity to yellow and red is reduced." NDT page.

Overall my conclusion is the either our star has changed its spectral output to a much green/ yellower colour OR human origins began in the environment of a RED/ BLUE star (?redgiant?). In either case our brains have simply adapted to these changes rather than evolving a complementary optical response. This is good news for the TV manufacturers and Dave Talbott .

I could go on to discuss the chlorophyll in most leaves which reflect GREEN and absorb RED and BLUE. But that could be another thread!

[tayga]

What an interesting perspective! As soon as I saw what you were discussing I thought of the Saturn argument.

A couple of Devil's Advocate questions occur to me.

1. Is it reasonable to assume that, given enough time, a biological system will always evolve to achieve optimal performance in a given environment?

2. Could the recognition of foods impose the greatest selection pressure on the development of colour perception resulting in highest sensitivity where the most discernment is needed ie amongst the various hues of green?

[cigarshaped]

Thanks for the response.

1. Is it reasonable to assume that, given enough time, a biological system will always evolve to achieve optimal performance in a given environment?

That would be a question for the experts. It may require looking at research on non-human eye characteristics. Is there adaption in other species?

2. Could the recognition of foods impose the greatest selection pressure on the development of colour perception resulting in highest sensitivity where the most discernment is needed ie amongst the various hues of green?

This question will also relate to my plant leaf colour thought. We end up with green leaves because of red/ blue light, and hence the need for additional Green senstivity to see what would appear a darker hue, under those conditions. A nice experiment to set up! The insects may have benefitted from higher (Saturnian?) UV levels and the plants took advantage in their coloration, still present today.

[tayga]

2. Could the recognition of foods impose the greatest selection pressure on the development of colour perception resulting in highest sensitivity where the most discernment is needed ie amongst the various hues of green?

This question will also relate to my plant leaf colour thought.

I thought that even as a I wrote the question. This is a really interesting line of enquiry and I'd be willing to bet that alternative explanations (to evolution under a different star) are complex and tenuous.

[cigarshaped]

Just to pile on the evidence, since response is a bit slow.

1) Our increased cancer risk is considered a result of low Vitamin D levels. Note that Vitamin D3 is produced via the skin by UVB radiation (peak 295 and 297 nm). UVB comes from the Blue (low wavelength) end of the spectrum, where our eyes are at their LEAST sensitive. Logically we are likely to originate from an environment in which Blue was the predominate colour of light. Hence a healthier life source benefitted our forebears?

2) Comparing animals - Chimps and monkeys match our spectrum pretty closely.
Lizards also follow our peak sensitivity. But interestingly the logic is the reverse of mine:

We suggest that the convergence of the shape of the photopic ERG-determined spectral-sensitivity curve in many terrestrial vertebrates may, in part, be due to the fact that the background radiance of many terrestrial habitats is dominated by the reflectance spectrum of green vegetation which peaks at 550 nm.

Do your eyes need to be more sensitive to something that is prevalent and in highest illumination levels OR to wavelengths that are the hardest to recognize because they are LOWEST luminance (eg illuminated by the blue/ red source)??

Haven't read all the evidence yet.

[tholden]

You're saying that the evidence indicates a former star producing green light? I mean, that IS what you read in the pyramid texts.....

[tayga]

You're saying that the evidence indicates a former star producing green light? I mean, that IS what you read in the pyramid texts.....

The two spectra in the OP suggest that the eye is sensitive to a redder spectrum than that of the Sun. If colour vision evolved under a red sun it would have occurred along time before human records.

I'm not sure anything in the Pyramid texts talks about a green star specifically. The 'green eye of Horus' might be any of a number of planets that were visible to the ancient Egyptians.

[cigarshaped]

Our eyes and that of birds have high green sensitivity, which means medium wavelengths were in short supply. The redder 'sun' would also have had a much higher UV/ blue content.
Tetrachromatic birds and reptiles have continued development from dinosaurs and even sea origins. Their 4th cone set is solely for UV rays. Interestingly they are better equipped to deal with a change of lighting, due to their adaptive 'oil droplet' technology. This acts like optical filters, and according to Prum, means they can physically evolve into new situations, by changing the oil colour. The number of cones doesn't seem to vary, so goes back a long way.

My suggestion is that human (and higher mammals?) are equipped with an alternative method to compensate for changes in light source. Our eye retains its mix of cones from prehistoric times and our 'software' eye/brain system adapts almost instantly to varying colour temperature. We recognize white objects under amazingly varied lighting, by comparing colour differences.

Should we be viewing ancient paintings and rockart with purple glasses to simulate our forebears viewpoint?

[tayga]

Tetrachromatic birds and reptiles....

Have you established how long ago tetrachromia developed and when those of us who don't possess it diverged from those who do?

Should we be viewing ancient paintings and rockart with purple glasses to simulate our forebears viewpoint?

That's a tough one but I'm satisfied with the interpretations of those Egyptian inscriptions which associate red with Mars and green with Jupiter. Extending that interpretation back to about 8000 BC might be possible but beyond that it may well be that much earlier Cro-Magnon cave painters used what colours they had rather than what they would have preferred.

[cigarshaped]

According to a brief but profitable conversation with Prof Richard Prum (yale.edu), "The complex, four colour vision originally evolved in fish, an adaption for some aspects of aquatic environments."
"Colour vision was lost (with the blue and green opsins) in the ancestor of placental mammals during millions of years in which we crawled around in the dark trying to keep from being eaten by dinosaurs."
And in his opinion "..our colour vision is a poor retrofit version of the bird-reptile-fish colour vision.....Very little about this is optimized for anything. It's just the best we can do having to reinvent color vision in our monkey ancestor."

I have to disagree with his poor opinion of human sight. I think it is an absolute marvel, and was well adapted to where we were 10,000+ years ago. But he's the prof!

[tholden]

Another question...

What about deer? Bambi's vision is heavily slanted towards blue and ultraviolet and in fact they now sell chemical sprays to knock the ultraviolet sheen which some detergents produce off of hunting apparel, guys were actually going out in camo gear which stuck out like a red flag for Bambi.

[cigarshaped]

For those of a microbiological background here is an answer I received, from HHMI Ask a Scientist:

Question: Where is the logic in Nature? Plant leaves are Green, yet sunlight is CURRENTLY richest in Green/ Yellow wavelengths. It should be Blue/ Red surely? Our eyes are also most sensitive in the Green area. Are there any creatures adapted to how the Sun is now? Can the Sun change its colour?

Here is a response provided by one of our volunteer scientists:

Good question. It is pretty clear that photosynthesis began in cyanobacteria, and that the endosymbiosis hypothesis explains the origin of chloroplasts in photosynthetic eukaryotes. So presumably, the bacterium that originally invaded its host cell happened to use chlorophyll rather than other pigments. Most likely, this event occurred in the primordial oceans, where blue light penetrates deeper (high energy photons), which might have been the ultimate selective advantage for the evolution of bacterio-chlorophyll, as opposed to other light absorbing pigments. There are many archae bacteria that use pigments that can capture green light, so when chloroplasts evolved there may have been a particular niche readily exploited by absorbing other wavelengths. It is possible that there was a negative selection component to bacteria harboring pigments that absorbed green light. Robust absorption might have led to to much heat generation and thereby damaged the cell.

The sun's color will indeed have changed because the atmosphere has changed. The UV protection now afforded us by our oxygen and nitrogen atmosphere also scatters the blue light the most - hence the sky is blue. When earth was young the atmosphere was full of other gases like methane and hydrogen and the sky would have been more orange. The sky turned blue as oxygen got pumped into the atmosphere by photosynthetic bacteria. Some speculate that about 250 million years ago the sky may have been more greenish due to high amounts of methane calthrates, and the great dinosaur extinction would have been under red skies due to dust.

Evolution is not an engineering process, and so it is often subject to various limitations that an engineer is not. Evolution's limitations can prevent an organism or species gaining optimal fitness in natures landscape. So, although our design for light energy capture would optimally select black, early photosynthesisers were under constraints that we can only speculate upon.

[cigarshaped]

Plants have been around longer than any animals so let's see what light they have evolved to flourish in.

Chlorophyll absorption spectrum

Chlorophyll is a basic requirement for photosynthesis and yet it reflects GREEN light. Funny that our current star peaks near the green (530nm), but falls off in Blue and Red, where the plant absorbance is maximum. If a previous 'sunlight' was predominanantly red/ blue, with high UV, then lush vegetation would have covered the world. The animals who lived in this environment, and the humans who were born into it, had eyes adapted to that light. Hence we needed a high green sensitivity to compensate for the lack of green light.

Thus our eyes and the plants point to a red-purple world, with higher UV. Thus a need for strongly pigmented skin which ties with the DNA search for Original man, who apparently came out of southern Africa, wherever that was on the globe. I'm a freak, my skin is pale my eyes are blue ... I probably would not have survived on an early Earth.

[Xuxalina Rihhia]

This is the kind of like Saturn gave off when it was an independent system; Uranus and Neptune most likely were stars as well and glowed like Saturn in a Herbig Haro configuration.

[tholden]

This is the kind of like Saturn gave off when it was an independent system; Uranus and Neptune most likely were stars as well and glowed like Saturn in a Herbig Haro configuration.

The last prior post to this thread was from November 2012 i.e. before Troy's and my book came out.

What we know now is that human eyes were never made for Saturn's purple dawn; they were made for light in a world illuminated by both Jupiter and our present sun:

http://www.cosmosincollision.com



That sort of gives you your red and green when you think about it.