It is always so disturbing to find out that what little learning you did back in high school was just learning crap.
I recall being taught, and later reading in newspapers, that green eyes were “fat” blue eyes. I.e., mixing yellow fat with blue eyes created green eyes. Of course, I remember reading a newspaper article that claimed blue eyes looked blue because they have no pigment, and so took their pigment from the color of water. Which has got to be crap, unless this collagen acts like a fiber optic tube. But, it brings up my next question. How does this “arrangement of collagen” turn eyes blue? Collagen is made of proteins, correct? Is it a blue substance, or is there some more clever optics going on e.g., diffraction grading?
As far as green eyed Berbers and Central Asians are concerned, could one argue that the ancient Romans, Germanic tribes (N. Africa), and Scythians (Central Asia) are responsible for “migrating eye color”. (Were Slavs always blue eyed? Or did they get it from the early Swedes and such?) Even if so, I suppose such migrations would help point out what crap race is, biologically speaking.
(a) There is no way of knowing what eye color the Slavs are, it is a linguistic label, language affiliations do not fossilize nor are they easily associated with populations in a clear manner.
(b) Roman intrusion into North Africa, being as Italic peoples are not generally fair or blue eyed ex-Celtic or Germanic intrusions, is hardly likely to shift NA demographics’ the Teutonic angle has been asserted, however the mountain people are possibly the least likely to have been influenced by the Germanic invasions of the Roman period, which in any event of slight demographic weight and brief in their duration.
Cecil’s written on the subject of green eyes. And blue eyes don’t contain a blue pigment, but are blue for approximately the same reason that the sky is blue and that some birds have blue or green plumage.
Isn’t this the pigment responsible for freckles? Because there are certainly some individuals for whom freckles are a very significant aspect of skin color. Are there any populations with an increased incidence of freckles?
I’m not buying Cece’s explanation until I see some cites. And yes, the medium for the scattering of blue light in the iris is collagen, a structural protein; same answer, different emphasis.
Some people have the majority of their melanocytes turned off (or way down); a few that produce lots of pigment are respoinsible for freckles. I suppose it’s possible that such people are producing mostly phaeomelanin, but I didn’t see any cites indicating that phaeomelanin contributes significantly to skin color in ANY population.
Ok, I found a nice explanation of human eye color, including the “two gene model” that I remembered from days of yore: http://www.athro.com/evo/gen/inherit1.html. It also nicely mentions what is not yet understood.
I know why the sky is blue; I have even gone through the scattering calculations. I don’t understand how collagen, which I presume is much larger than any inorganic molecule, can scatter blue light so effectively. (If I remember the calculation correctly, the wavelength and the size of the scattering must be somewhat comparable.
No, I haven’t been able to find a link that explains the physical process leading to blue eyes, anymore than green - aside from good ol’ Cecil.
SlowMindThinking, you can’t put a period after a URL.
The two-gene model sounds fine, but there’s apparently no agreement on why green eyes are green, and there’s uncertainty as to whether it’s really three genes. It’s still an egg.
I’m not going to try any calculations, but I suspect you’re ignoring a few things: light is reflected from the iris, instead of passing through it; light is also reflected from the pigment epithelium, and acquires color there before passing through the iris; even blue eyes contain some melanin, and the particular shade of blue or grey depends partly on this, as well as on the factors already mentioned.
Besides, it’s my experience that anything that’s colorless and translucent will appear blue if you have just the right thickness of it.
Sorry about the link and the period. I know better.
I’ve been poking around, and not working, trying to find an explanation of why blue eyes are blue. I figure why green are green will follow. (For the record, no one seems to have any idea what color mine are. Mine are “strange”, which is a reflection of my sole.) Most physicists seem to happily state that eyes are blue for the same reason that the sky is blue, but not all. E.g., http://micro.magnet.fsu.edu/primer/lightandcolor/primaryhome.html
states
I think we all know that reflection and scattering aren’t the same, but how is this from a slow mind thinking [poorly?]. Blue eyes certainly don’t come from water scattering light, or our bottles of Aquafina would all appear blue.
Surely albinos tell us something about what color unpigmented eyes appear. From what I’ve read, their eyes appear pink and not blue. I presume they still have collagen, unless the collagen serves no purpose other than to provide eye color and the genes for “eye collagen” are identical to the pigment genes elsewhere in the body. The pink, presumably, is a tinge picked up from blood vessels, much like red eye.
For blue eyes to appear blue, some frequency must either be mixing with the red to produce blue or overwhelming the red. Since blue is a primary color, I vote for the latter, but I won’t claim I understand the human perception of color. So, if albinos have collagen in their eyes, and no pigment, then blue eye color must come from something other than light scattering off of collagen.
Eh…eye color depends on different genes. One of those genes controls the blue layer of color. The only way to express that gene is to have two copies of it. Other pigments may vary the final eye color or not.
Oops. I type these things while talking at work. I’d like to claim we were talking about sole possesion of something like first place, but most likely it was just a brain fart.
I did talk to some physical therapists over the weekend. They had actually worked with some albinos, and not just seen them on some cheesy tv show. Apparantly, their eyes are blue, so I believe the scattering explanation, I just don’t know how it works.
Google “Ainu” and you’ll get a huge amount of hits. I couldn’t find a handy photo, but they certainly look Asian to the untrained eye, and are the most hirstute people I’ve ever seen. I mean, I get people who think I should take a weedwhacker to my legs, arms and back, but that is nothing compared to the handful of Ainu I encountered during a trip to Hokkaido about 13 years ago. IANAAnthropologist but they certainly did not look even remotely “caucasian”
Or, since it’s just melanin that albinos are lacking, it could simply be that the blue comes from another blue-colored chemical. That may be a pigment, or may even be for the same reason veins look blue under your skin.
Irishman: You might find this essay of interest, which describes the origin of the five ( four ) race concept as part of a discussion of the issue of race in North America:
Well, while you’re waiting, you might run a search on the subject:
Entering “linnaeus races” into Google turns up a number of sites that provide some information on the subject:
At http://www.english.upenn.edu/~jlynch/Frank/Contexts/physanth.html they note that Linnaeus did mix culture and physiology to create his seven categories, but that his student Blumenbach discarded cultural factors, relying solely on (his perception of) anatomy, giving us the “Five” races that are familiar to many people.
Following up that search with one on “blumenbach characteristics racial” we find several more citations, including http://dimensionsnews.com/nomenclature_of_race.htm
that includes the following two statements:
(Why did he pick those categories? You may have to go read his original text.)
Thanks for the cites. Those sources don’t really answer the question itself. You would think a racist snob (or someone set to make distinctions in human types by skin color and physical features) would look at a dark-skinned Indian and think, “No way is that a proper white man. He must be a different race.” Similarly with Arabs. So why did they get included with caucasians?
I note that two of those links state different reasons for Blumenthal to pick caucasians as the ideal standard. One states it was because of skull shape, but another states it’s because he thought the women of the region were the most beautiful.