The paper referenced says nothing about eyes.

[Seems a little weird to me that vitamin consumption would prevent evolution's adjustment to the environment, but what do I know.]

This is plausible. The Inuit diet is heavily based on foods high in vitamin D from the sea whereas the Viking diet is based on herd animals and their milk which are not high in vitamin D. Jared Diamond wrote about this in his book titled "Collapse" as to probably reasons why some of the Viking colonizations failed. They refused to adapt to feeding themselves from the sea.

With the pale European Northerners, there were other selection pressures contributing to the gene pool. It seems that the Northern Asian people didn't have the blondism and blue eyed genes spreading like wildfire like the European people did. But this is combined with the fact that they weren't eating fish livers all the time and relied more on domesticated hooved land animals for food.

Different selection pressures, different starting populations=> different results.

Another potential contributing factor is that UVA does not vary nearly as much with latitude as does UVB, and since the wavelengths of rays in the action spectrum for D synthesis (UVB, which varies a lot with latitude) are so different from UVA (which does not vary nearly as much with latitude) one might expect that other things contribute to the coloration differences in skin color, at least in some populations.

Most Northern Asians who are not of Arctic descent are paler than their Southern counterparts and noticeably paler than the Inuit. Increased exposure to UVA via reflections from the snow and sea probably contributed to this difference. Darker skin means less synthesis of vitamin D for a given level of sun exposure; they had to make up for this difference in their diets, otherwise they would have died, likely before reaching adulthood.

Vikings were from area that did not get sun for a long time. Like some parts of Norway, it's dark a lot and then they have the 'midnight sun'. Blond blue eyed is RECESSIVE gene. So if Vikings invade area where dark hair, dark eyes is dominant and start mating with the locals, probability is in favor of the offspring having the dark eyes and hair.

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Can hardly walk. Need hip replacement.

[Blond blue eyed is RECESSIVE gene. ]

Yes, of course. But it has a heavy prevalence in some regions, due to selection pressures. The Inuit haven't been North for very long compared to Northern Europeans. If they quit eating their vitamin D, in 30K years or so they might lose their pigment, too.

[Cut and pasted from the end of the fourth paragraph of the article.]

I had read the Jablonski paper referenced within. The website article doesn't have a reference for that statement. I think they made a mistake and meant melatonin.

http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/pineal.html

No, as I previously stated, I think they made a mistake in the article. Mistakes in the lay literature are very common. Heck, they are common even in technical journals.

[ Does this mean that if someone takes melatonin supplements they would in turn also get darker when they go out in the sun?

No, I don't think there is any correlation.

[ There is some in-vitro evidence supporting that leptin suppresses melatonin production as well. Maybe taking leptin would keep someone from dark patches from the sun.[/quote]

There is probably some melanocyte response to many neurotransmitters, neuropeptides and hormones that might be attenuated or augmented by UV radiation. As yet, there is the biggest body of evidence for sex hormones. Melasma and other pigment disorders are heavily influenced by sex hormones.

But there haven't been any in vivo tests on melatonin showing its affects on any aspect of the tanning response.

There were some test tube studies where melatonin protects melanocytes from the damaging effects of UVA and UVB because of its antioxidant activity. Also (edited to add this) it has been shown to protect humans against burning when applied topically.

As far as I know, melatonin is NOT related to tanning. It's related to sleep cycles. Melatonin is something to take after having jet lag or before bed time as it helps regulate the sleep cycles. Leptin is some kind of hormone having to do with FAT.

If you want to get darker in the sun people used to take some cartinoid for that. Think it was called 'canthaxin' or something like that. Body builders used to take it to get a tan easily.

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Can hardly walk. Need hip replacement.

Yup, it doesn't take much to get sunspots or darker skin. I don't have children so I have an easier time avoiding the sun in the summer but it's a full time job, keeping the arms covered while in the car, making sure I always have a hat, making sure sunscreen is in place, timing certain activities to avoid the sun. I miss my old carefree self. I've learned the only way to avoid getting a tan and preventing more freckles is to stay completely out of the sun; wear long sleeves and huge brimmed hat. Sunscreen doesn't work completely and in my opinion, provides a false sense of security.

Mine does not work because it's always being rubbed off my NOSE from allergies to the pollen. I'm just going to stick a LEAF on my nose for sun block.

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Can hardly walk. Need hip replacement.