Blue-eyed Humans Have A Single, Common Ancestor

[Matt]

EDIT: Then again, if both parents carry the same gene (which they would need to, as you say), then how can the researches be sure that there is only one common ancestor and not two, or more? Hmm.. something's not right.

I guess whoever had the blue eye gene first can be considered a common ancestor.
This wouldn't be true if there have been two individuals who got that mutation independently from each other but I think the researchers checked that possibility. I guess this is where probability and statistics come in.

I think there would need to be two instances of that mutation, otherwise it could not pass to another generation because it is recessive (?)  So the first common ancestor can't be the first do develop the mutation, but merely the only common link we have today. But that last part is the thing I don't know how they can prove (that he/she was the only common ancestor), considering there must have been more than one instance at some time before that.

EDIT: Maybe I should just read their paper. These journalistic articles never explain these things correctly anyway 

Matt

[SeerBlue]

 There would need only be one mutation, say Bob is the first to be born with blue eyes ( he probably would have caused quite a stir, wouldn't he), he then has children and passes his blue eyed gene onto his children, but his mate passes on the brown eye gene, since one theory says that only one correct gene is needed to create brown eyes, the children would be brown eyed, but would carry a blue eyed gene as well.
One set of genes from the Father (blue) and one set from the Mother (brown).
Their children have children, and as it is random chance to which gene they pass on, brown or blue, in later generations the chances increase that a child will again end up with two blue eyed genes and have Blue eyes. Quicker in a smaller population base, due to intermarriage.  Then the whole cycle starts again.
If both parents are Blue eyed , theoretically they should not be able to give birth to a brown eyed child, they would not have a working copy of the brown eye gene, yet they do have brown eyed children. So it is thought there is another gene involved that has not been found yet (green eyes?) that also plays a part.
This Common ancestor (or the Blue Eyed Adam/Eve), and Most Recent Common Male/Female Blue Eyed Ancestor (the latest individual we all share in our family tree with blue eyes), would be two different things, as is Chromosomal Y Adam(the earliest common male ancestor),  and MtDNA Eve.
Genetic testing will probably find other common ancestors who introduced genetic mutations into the dna, some of which are all inclusive and others which cover only a subset of the population, can you say lactose intolerant.
You are related to a lot more people than you think, the first 20 generations ( about 400 years at 20 years to a generation, though the US avg is now about 25 years) above you are something like this 2, 4, 8, 16, 32, 64, 128, 256,  512, 1024, 2048, 4096,  8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576..(odd how it follows the original terragen image ratio, isn't it)... so some of my 1,048,576 ancestors who comprise my 20th generation MAY to be in your line. Go further back, say 3000 years and they HAVE to be in your line (as the increase is exponential 80 generations, 1600 yrs, is like a trillion trillion people, if none of them were common, so they have to be),  These are not your traditional paternal or maternal surname ancestors most people track but all parents of parents of parents,,,
SeerBlue

[Matt]

Seer: Ah! I completely forgot about that. Thanks

[SeerBlue]

No problem, the blue eyed thing has always interested me as in my family tree 2 distinct Smith families intermarried in about 1794, a male descendant of Reverend Henry Smith, named James, and a female descendant of Lt Samuel Smith, named Elizabeth.
The branch Lt Samuel Smith is described in period literature as having males who are blue eyed and blond, and the other, that of Reverend Henry is described as dark eyes and hair. So theoretically, this could be where the Blue Eyed gene entered my maternal line. My parents are both brown eyed, though I have siblings who have blue eyes.
It may well have been introduced or reintroduced, at other points, but it has made for interesting research.
Genetic Y chromosomal testing,  has shown that direct paternal descendants of Rev Henry and direct paternal descendants of Lt Samuel,  are not related, though they are both R1B1, Western European, so perhaps someday this blue eyed thing can narrow down where Lt Sam's ancestors originated.

SeerBlue

[crosseout]

Ya, you are right, there can be only one ancestor. Genetics is a subject not always correctly understood. You have to apply it to social dynamics and human psychology as well. Let's say there is born a blue eyed baby (male, not female) somewhere in central asia 10 000 years ago. Blue eyes were previously unheard of, and would therefore be considered very special, so special to the point that the tribe of perhaps 60 people the baby was born into considered him not just a decendant from a god, but a god. This would probably cause the blue eyed boy to inseminate every girl and woman from he got into puberty and til his death as monogamy after all is a new idea. There would probably be little competition from other males as he was after all, a god. There would probably be about 20-30 females in fertile age (people didn't live very long), which would make for several offspring, probably 1 every 4 years for each woman and a pretty high infant death rate (probably more than 50%). When these children grew up, they were all carriers of the blue eye gene, but none of them would show it as it was only their father who had the allele. What happens next is in-breed, a lot more than was usual. Since almost all the children in about 20-30 years have the same father, they won't have many other choices anyways, so they mate with each other and about 25% of their children would have blue eyes, now they were considered special as well since it was about 30 years since the first blue guy died. They do some in breeding again and there we go, in-breed all the way...

What really amazes me though is how the h**l they survived. Our most deadly enemy is the bacteria; more people died from diseases than from any other cause. So the gene's way of handling this is with pheromones; one will only be attracted to persons with different immunity systems in order for their offspring to gain information of how to fight diseases from two different sources with different information. This however would not be the case in the blue eyed village, and it is truly lucky that they survived long enough to spread blue eyes to the extent they have without being wiped out by some plague... oh well...

[Will]

I am your father!

[Cyber-Angel]

I am your father!

No! No! No!,Thats...Thats impossible.



Regards to you.

Cyber-Angel   

[SeerBlue]

Will, I seem to remember, or misremember, that you are from NH,,where I misspent my youth ,,,I may well be your father ...
Not really, I was in Europe for my wild years,,,but I do have Walkers in my family.
SeerBlue

[SeerBlue]

Good point about the pheromones crosseout, it is also thought that on a very basic level, more in the early days than now, females would choose, for many reasons and your's included, a mate that would give the best chance of healthy offspring, and who was much different than her family unit, to mate with, but would marry or bond with a male who was  similar to her own family to raise her children,thinking they would increase the chance of long term survival,,so the blue eyed village would have it tough.

perhaps giving rise to the saying "he married his mother"
SeerBlue

[SeerBlue]

this is interesting
"One survey estimated that nearly 90% of Icelanders have blue or green eyes. Blue eyes are often found in Northern European countries, and are most common in Ireland, Germany, Netherlands, Iceland, Austria, Sweden, Norway, Denmark, Finland, Estonia and the United Kingdom. [26] They are also present, to a moderately lesser extent, in Southern Europe, the Middle East, Afghanistan and India. A 2002 study found the prevalence of blue eye color among Whites in the United States to be 33.8% for those born between 1936 and 1951 compared to 57.4% for those born between 1899 and 1905[/font].[7]"

Larger population, less inter-marriage, fewer blue-eyed people, guess you are all on your way to becoming an oddity once again

[Will]

Will, I seem to remember, or misremember, that you are from NH,,where I misspent my youth ,,,I may well be your father ...
Not really, I was in Europe for my wild years,,,but I do have Walkers in my family.
SeerBlue

Hehe yep am a true Yankee.

I've personally always been interested in the yellow eyes of Attila the Hun.

[crosseout]

Well, females in our society today respond to certain types of behaviour differently, just as they would back then. As a matter of fact women are very attracted to alpha-male behaviour such as confidence, preselection and so on... Women feel a strong urge to sleep with the alpha male as fast as possible. However, the alpha-male usually have a lot of women and thus divided resources. Therefore the woman would find someone who could support them the 4 years they needed it. Get another man to raise another man's child because his genes are not sufficient for the woman(;

This pattern of behaviour can also be seen today; the women who are unfaithfull often (probably unconciously) have more sex with her lover when she has a high chance of getting pregnant, but not at those times with the husband.

As for the blue eyed people over in india and afghanistan, it can be explained by the origin of the blue eyed people which was in central asia from where they migrated southwest to north india. There they introduced the caste system to keep the population under control before they kept moving west.

The diminishing of blue eyed people is due to the dominance of brown eyes...

[nikita]

Well, females in our society today respond to certain types of behaviour differently, just as they would back then. As a matter of fact women are very attracted to alpha-male behaviour such as confidence, preselection and so on... Women feel a strong urge to sleep with the alpha male as fast as possible. However, the alpha-male usually have a lot of women and thus divided resources. Therefore the woman would find someone who could support them the 4 years they needed it. Get another man to raise another man's child because his genes are not sufficient for the woman(;

I.. simply don't share these views. We're talking about blue eyes here... I'm pretty sure most woman also look for other things than the color of the eyes 

[Will]

Interesting read

http://www.cnn.com/2008/TECH/04/24/close.call.ap/index.html

[nikita]

Heh.. I don't think I'll understand much of that paper 
(http://www.springerlink.com/content/2045q6234h66p744/)