Blue-eyed Humans Have A Single, Common Ancestor

[Godwynn]

if you are all descended from one human, and given that the blue eye allele is recessive, that means you are also sons and daughters of an incestuous relationship... enjoy your eye colour.

Hm... if I remember my biology correctly, recessive genes can reappear in the F2 generation with a 25% chance, don´t they? (or do they? my brain hurts)

Because... if only a single human developed this trait which is recessive - how did that trait spread at all? Okay, the information "blue" is still stored, it is just in the genetic "background" - but how did it spread then?

edit: I will enjoy my blue eyes immensely, because:



(http://www.livescience.com/health/080131-blue-eyes.html)

I think I have mentioned it before in this thread, but it is a paternal trait in my family. Both my mother and paternal grandmother had dark brown eyes, yet my father and I both have light blue eyes.

I don't think it is as simple as "one blue-eyed parent and one brown-eyed parent, brown automatically wins because blue is recessive."

 

[GoodGame]

Hm... if I remember my biology correctly, recessive genes can reappear in the F2 generation with a 25% chance, don´t they? (or do they? my brain hurts)

Generally correct, by Mendel square (Edit: Punnett square). Though phenotypes might be a complex of multiple genotypes.

If blue eyes started as a mutation of a single individual, and was a recessive trait, a tight breeding pool (e.g. incestuousness or at least borderline in-breeding) could get the numbers up so that by modern times, so no inbreeding needed in recent times(so no reason to suspect your great greats of swimming in their family pool).

 

[Chieftess]

I have 1 blue/hazel eye, along with 1 brown eye.

(Gee, I wonder who I'm related to in here...)

 

[Birdjaguar]

I have 1 blue/hazel eye, along with 1 brown eye.

(Gee, I wonder who I'm related to in here...)

Have you ever lived in Bath?

 

[Chieftess]

Have you ever lived in Bath?

Nope, never been on that side of the pond.

 

[tycoonist]

I think I have mentioned it before in this thread, but it is a paternal trait in my family. Both my mother and paternal grandmother had dark brown eyes, yet my father and I both have light blue eyes.

I don't think it is as simple as "one blue-eyed parent and one brown-eyed parent, brown automatically wins because blue is recessive."

phenotypes of the older generation do not necessarily have any implication on phenotypes of the younger generation. and, i don't think there is is anything paternal about it.

Fathers genotype: bb (phenotype: blue)
Mothers genotype: Bb (phenotype: brown)
Possible genotypes for offspring (i.e. you): bb, bb, Bb, Bb
Possible phenotypes for offspring: Blue, blue, brown, brown

so you had a 50/50 chance of having blue eyes or brown eyes.

it definitely isn't as simple as "one blue-eyed parent and one brown-eyed parent, brown automatically wins because blue is recessive." But if the brown eyed parent is homozygous dominant, then the child will always be brown eyed. if the brown eyed parent is heterozygous, then the child will have an equal chance of being brown eyed or blue eyed if the partner is blue eyed (as blue eyed is always homozygous recessive).

 

[tycoonist]

Because... if only a single human developed this trait which is recessive - how did that trait spread at all? Okay, the information "blue" is still stored, it is just in the genetic "background" - but how did it spread then?

see my above post, but basically two brown eyed parents can be carriers of the recessive genome: i.e. they can be Bb.

if two "carriers" mate, they have a 25% chance of producing a blue eyed child, and a 50% chance of producing a heterozygous child, and a 25% chance of producing a homozygous dominant (i.e. BB) child.

But if this genome originated in a single human with mutated DNA, then blue eyes must be in some way linked to an incestuous relationship. but yeah, enjoy your eye colour. i enjoy brown just as much

 

[StarWorms]

What about my friend whose eyes changed from blue to brown?

 

[StarWorms]

phenotypes of the older generation do not necessarily have any implication on phenotypes of the younger generation. and, i don't think there is is anything paternal about it.

Fathers genotype: bb (phenotype: blue)
Mothers genotype: Bb (phenotype: brown)
Possible genotypes for offspring (i.e. you): bb, bb, Bb, Bb
Possible phenotypes for offspring: Blue, blue, brown, brown

so you had a 50/50 chance of having blue eyes or brown eyes.

it definitely isn't as simple as "one blue-eyed parent and one brown-eyed parent, brown automatically wins because blue is recessive." But if the brown eyed parent is homozygous dominant, then the child will always be brown eyed. if the brown eyed parent is heterozygous, then the child will have an equal chance of being brown eyed or blue eyed if the partner is blue eyed (as blue eyed is always homozygous recessive).

It's far more complicated than that and I know you're trying to simplify it but you're implying it's just a single gene that controls eye colour. Hair and eye colours have many different genes. It's more like a spectrum which goes from a deep brown through hazel and green to blue, and then grey. Certain genes influence it one way or another.

 

[tycoonist]

It's far more complicated than that and I know you're trying to simplify it but you're implying it's just a single gene that controls eye colour. Hair and eye colours have many different genes. It's more like a spectrum which goes from a deep brown through hazel and green to blue, and then grey. Certain genes influence it one way or another.

everything i have said is true - that is to say, blue is a recessive colour and brown is dominant. however, you are correct. multiple genes further determine eye colour - specifically the amount of pigment present in the eye, which is what leads to other eye colours such as as green and grey. indeed, it is even possible to get red eyes through rare genetic mutations.

EDIT: and i have no idea about your friend - it sounds like an environmental change - but i really have no idea.

 

[Arakhor]

I have mostly blue eyes to go along with my mousy hair. I used to be perfect blue and bright blond but then I aged

 

[Grey Fox]

I have blue eyes.

Also, I think I heard something about all males have a common ancestor from 80,000 years ago.
While all females can be tracked back to a single female 120,000 years ago, or so.

 

[Godwynn]

I have blue eyes.

Much to your dismay, we are related.

Now you're going to have to suffer through me at Christmas!

 

[MagisterCultuum]

I have brown eyes, but my sister and both of my half brothers have blue eyes.

On the day my (blue eyed blond haired, despite being 1/4 Chinese) nephew was born, I noticed that my eyes looked green, at least in the florescent lights of the hospital bathroom. I don't just mean a little green, they had a vibrant emerald hue which I think looked a lot better on me.


Both of my parents have green eyes. My dad had brown eyes much like mine when he was young, and his eyes had turned hazel by the time my parents met and today his eyes are greener than hers. His mother had blue eyes and his father hazel eyes.

My mom has always has olive green eyes, but every other female in her family had blue eyes and every male brown.

I have blue eyes.

Also, I think I heard something about all males have a common ancestor from 80,000 years ago.
While all females can be tracked back to a single female 120,000 years ago, or so.

From what I read tracing mitochondrial DNA found all humans likely share a common mother a mere 100,000 year ago.

I also read that a few years after that was published, it was found that human mitochondria actually mutate about 20 times faster than the estimate used in that study, which could fit YEC claims.

 

[Perfection]

But if this genome originated in a single human with mutated DNA, then blue eyes must be in some way linked to an incestuous relationship. but yeah, enjoy your eye color. i enjoy brown just as much

Huh? Every relationship is in some way incestuous? Are you trying to imply something more here?

 

[xcrissxcrossx]

I haven't read the entire thread, so someone may have said this already. Blue eyes are a recessive gene, which means that both parents must have at least one of the genes to pass it on to their children. It is way more likely that the person who first had this defect only had one defected gene, which means the first blue eyed person actually had brown eyes.

If you think deeper into it, whether he had one or two of the defected genes, the only way anyone else could have blue eyes is if there was someone else with the gene, and they both mated, and the only way there could be someone else with the gene is if he had children. If you consider the amount of blue eyed people today, that means only one thing. Lots of incest.

 

[Shibbyman]

Would it be possible that the prevalence of the trait in Europe is due to founder effect, a population crash in Ice Age Europe or any something similar without large scale inbreeding if the trait had occurred earlier enough for there to be a significant population of heterozygous carriers?

 

[peter grimes]

It does not at all imply incest.

 

[Shibbyman]

It does not at all imply incest.

I know, that's the point I'm making. A lot of people in this thread seem to be thinking that though...

 

[Quackers]

Hazel eyes here. But my mother had blue eyes and therefore I carry the allele - the wonder that is the human race. I think one day Blue eyes wn't exist.