Is it possible that there’s some connection between the low-melanin genes in eyes and the low-melanin genes in skin? And hair, for that matter. In that case, it could be the advantages to fair skin that drive the spread, with blue eyes just coming along for the ride.
Well there doesn’t seem to be. You can have very dark skin and low-melanin eyes. And eye color appears to be ruled by just a few genes with low-melanin being recessive, while skin color genes are more numerous and most are clearly intermediate rather than recessive.
The Mughal empire, IIRC, was an invasion from the Arab areas via Persia - just one example of the level of mixing of the various populations; and those areas have had their own mixings. It is no surprise then that there would be a visible number of mixed heredities from England and Scandinavia all the way to the Bay of Bengal.
(The famous picture of the Afghani woman on the cover of National Geographic, she appears to have strikingly light green eyes.)
Not exactly. Rashidun and Umayyad penetrations of the Hindu Kush and eventual conquests as far east as Punjab and Sindh in the 7th and 8th centuries were invasions from Arab areas via Persia.
The Mughals came along almost 800 years later and were Turco-Mongolian Timurids( descendants of my namesake ) from eastern Persia.
Why blue eyes? Because blue eyes are the best! 
For pilots. Why? Because pilots. 
This completely misses the point of the remark. Sexual selection can promote the spread of traits that are either otherwise neutral or actually even detrimental in terms of survival.
True, but they no doubt brought with them armies consisting of peoples they drew from all over their region, drawing on genetics that had easily mixed from over toward the Mediterranean. I’m assuming the rulers were not the only ones to leave their genes behind in the conquered lands.
The point being, there was plenty of mixing. Not to mention traders arriving by ship since the days of the Roman Empire and earlier. India was not an isolated land, probably better described as part of the continuum from Spain eastward; and enjoyed far more co-mingling with the rest of western civilizations than, say, China separated by thousands of miles of mountains and an arduous silk road journey.
(But even China sent ships to India…)
Just an observation: in the Rocky Mountain states blue eyes are quite common due to early immigration from the UK and Netherlands.
Curious, I did an informal study at work: of the nine of us who originated from the western U.S., eight have blue eyes; of 25 native East Coasters, three are blue-eyed. A lot of Italian and Southern European immigrants stayed put in the area as did Af-Americans who came North post-bellum.
Technically, a trait doesn’t need to have any benefits to be carried on – just as long as it doesn’t have any serious anti-benefits. So blue eyes may have no benefits at all.
They may be rare enough to trigger the sexual attraction often associated with rarity, so they get passed on. Which provides no benefits at all to the blue-eyed individual, but this trend toward diversity may be beneficial to the species as a whole.
I think you may be taking too clinical an approach here
That may be true in general, but in the specific case of blue eyes it’s been demonstrated that they did not spread by random chance but have been strongly selected for. What exactly the selective force was is still undetermined. The article suggests two possibilities, sexual selection and association with paler skin. The second possibility seems to be ruled out by the fact that the spread of blue eyes in Europe appears to have preceded the spread of pale skin, as demonstrated by the DNA of some early populations that had blue eyes and dark skin, as noted in the link in post #18.
Again, potentially true in some cases, but not for blue eyes, which are found in 80% or more of the population in parts of Northern Europe. Blue eyes were selected for long after they were no longer rare.
Blue or green eyes and darker skin is an even rarer combo than blue/green eyes and pale skin, so I would think if rarity was being selected for, that combo would be favoured. So it might be just the eyes.
The subcontinent has a “rust” phenotype, which means brown eyes, red hair and near bronze skin. Uncommon, but seen all over.
IIRC, white/pale skin has developed twice, once in Europe and the other in Asia, the European one is linked with light hair and eyes, while the Asian one is not.
Which frankly put paid to the theory that light skin came about due to sunlight concerns, Europe is not particularly cold, at least not compared to the continental areas of N America which did not see light skin develop, see Eskimos. On the other hand, people living in the sunniest places on Earth, i.e Arabs are still relatively light-skinned.
What does cold have to do with it? The issue isn’t cold but the amount of sunlight, and much of Europe is relatively cloudy. There is a definite correlation between human skin color (in native populations) and latitude in both the eastern and western hemispheres, although it is far from perfect.
Eskimos are lighter skinned than Native Americans living closer to the Equator, although still darker than northern Europeans. It is thought that the fact that their diet was historically rich in vitamin D sources such as fish oils compensated for lack of sunlight to produce vitamin D in the skin. Arabs are dark skinned compared to populations in Eurasia living farther north.
But a shade or so, not significantly like say sub saharan Africans .And they are much lighter than populations who live in jungled covered areas of the tropics which much less sunlight. Arabs probably get the most sunlight of anyone and yet they are not particularly dark. (Compare an Arab standing next to a person of N Euro descent)
Arabs haven’t really been a uniformly autochthonous population for long enough to matter on evolutionary timelines. That region has had significant inputs of genes from further north, like Alexander’s armies, Crusader kingdoms and the various Turkic hordes.
Arabs show a range of skin coloration, and can be quite dark, so cherry-picking images doesn’t prove anything.
As I said, the correlation of skin color with latitude is not perfect but it unquestionably exists. And it exists within different lineages such as Native Americans and Europeans, so it is evidently convergently developed and hence due to selection.
Firstly, that picture is from Egypt-Sudan border region, which is by any definition “Africa”. Secondly, I know very well about the range of Arab phenotypes, thank you very much, my point is that they don’t seem to have developed exclusively black skin like sub saharan Africans generally (with a few exceptions) have, despite being exposed to as much if not more sunshine.
Actually, according to the caption on the site it’s posted on, it’s from Yemen, which by any definition is Arabia.
Admittedly Yemen has more influence from Africa than most of Arabia. But then, being African does not rule out being Arab as well, since the Egyptian you linked to was an African as well.
As I have repeatedly pointed out, discrepancies like this do not invalidate the general correlation between latitude and skin color.
Do you have some new point to make?