RoR: Forum

Post 0

Thursday, January 31 - 6:38pm

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What is the evidence for this claim?

Bob Kolker

Post 1

Thursday, January 31 - 9:21pm

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oops...i must have stumbled on the science channel...can anyone point me the way to the Objectivist site??

Post 2

Friday, February 1 - 2:49am

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Good grief, Bob. Read the effing article. It's linked to the headline in this news item.

Phil,

I thought Objectivism had a love affair going on with science. I like to think it does, anyway.

Post 3

Friday, February 1 - 3:12am

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He's using the little 'i', Teresa, so perhaps is the little man in him complaining...;-)
(Edited by robert malcom on 2/01, 3:13am)

Post 4

Friday, February 1 - 6:44am

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By "this claim", Bob may mean the claim that all blue-eyed people have a single common ancestor. The article didn't really prove it to me. Any genetics experts out there? Can you explain why there is the assumption that a particular genetic mutation only happened once? Couldn't there have been separate occurrences of it all over?

Post 5

Friday, February 1 - 2:55pm

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Laure, for what it's worth, here is the relevant part of the abstract from this study followed with a recap:

Blue eye color in humans may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expression.

Eiberg H, Troelsen J, Nielsen M, Mikkelsen A, Mengel-From J, Kjaer KW, Hansen L.

Department of Cellular and Molecular Medicine, Section IV Build. 24.4, Panum Institute, University of Copenhagen, Blegdamsvej 3b, 2200, Copenhagen, Denmark, he@imbg.ku.dk.

The human eye color is a quantitative trait displaying multifactorial inheritance. Several studies have shown that the OCA2 locus is the major contributor to the human eye color variation.

By linkage analysis of a large Danish family, we finemapped the blue eye color locus to a 166 Kbp region within the HERC2 gene. By association analyses, we identified two SNPs within this region that were perfectly associated with the blue and brown eye colors: rs12913832 and rs1129038. Of these, rs12913832 is located 21.152 bp upstream from the OCA2 promoter in a highly conserved sequence in intron 86 of HERC2. The brown eye color allele of rs12913832 is highly conserved throughout a number of species. As shown by a Luciferase assays in cell cultures, the element significantly reduces the activity of the OCA2 promoter and electrophoretic mobility shift assays demonstrate that the two alleles bind different subsets of nuclear extracts.

One single haplotype, represented by six polymorphic SNPs covering half of the 3' end of the HERC2 gene, was found in 155 blue-eyed individuals from Denmark, and in 5 and 2 blue-eyed individuals from Turkey and Jordan, respectively.

Hence, our data suggest a common founder mutation in an OCA2 inhibiting regulatory element as the cause of blue eye color in humans. ...

Recap:

There's a part of our genome which affects eye color more than any other part does. This most-important (for eye color) part of our genome mutated about 10,000 years ago. When folks were divvy-ed up based on eye color -- everybody with blue eyes had the mutation; everyone with brown eyes didn't.

Post 6

Friday, February 1 - 3:40pm

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There is nothing preventing the same mutation from happening to two different copies of a gene.

My eyes are gray-green-yellow-brown.

Post 7

Friday, February 1 - 6:52pm

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Sanctioned Post #5 for the excellent English translation.

Post 8

Friday, February 1 - 11:31pm

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Thanks, Teresa.

One of my favorite things in the world to do is to make something formally-special materially-accessible (generally knowable). I really enjoy being a candle, but when I can't -- which is much if not most of the time -- I enjoy it nearly as much being a clarifying mirror reflecting its light. Hence, my fascination with learning and teaching and coaching.

Ed

(Edited by Ed Thompson on 2/01, 11:35pm)

Post 9

Saturday, February 2 - 4:49am

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In other words, Laure, the mutation didn't happen all at once in hundreds/thousands of different people. That would be a miracle. But, this would make sense if the mutation was influenced by an outside factor, something in the diet or environment, for example.

Ed, is it possible that a mutation in different individuals could be genetically identical if it sprang up randomly in, say, two different people residing in different parts of the world? I don't think it would, I think there would be a difference in the mutation's sequence.

Post 10

Saturday, February 2 - 10:48am

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Teresa,

Ed, is it possible that a mutation in different individuals could be genetically identical if it sprang up randomly in, say, two different people residing in different parts of the world?

It's possible though highly unlikely.

Key:
=======
base:
a unit of DNA

amino acid:
a unit of proteins; each one coded for by a different string, 3 bases long

gene:
a string of bases in DNA which codes for a body protein; something which is made up of several amino acids
=======

Our DNA is a complex, yet ordered, string of 4 different chemicals, called nucleotides or bases: A, G, C, and T.

In humans, this DNA string is a few billion units long and the 4 different bases are found in different orders. An active string of many bases in a row makes up each gene (which codes for our different body proteins); and there are 10s of thousands of human genes.

If you change (read: mutate) a single unit in the strand of DNA, then you might get a change in the function of the gene. Sickle Cell Anemia is a good example.

In the gene that codes for the body protein, hemoglobin, there can sometimes be a mutation in a single base. This point mutation causes a single switch in the amino acid sequence, changing just one amino acid out of about 140 of them. That difference -- that single amino acid change in a protein comprised of about 140 amino acid units! -- changes the shape of the red blood cell so that it resembles a sickle instead of an oval.

However, the likelihood of 2 folks getting that same base change -- rather than one person merely passing it on to offspring -- is pretty slim. Let's say that there's 3 billion bases in the human genome. That's 3 billion spots ripe for change. Each amino acid (which makes up our body proteins) requires a 3-base code. Not only do you have to get lucky and hit that spot that's 3 bases long (out of 3 billion bases), you have to make a change in that 3-base code to make it code for the same individual amino acid (of the protein for which it is part of the blueprint).

I could have said all that in 2 or 3 sentences, but I already warned you that I was fascinated by the learning process -- so don't blame me!

;-)

Ed

Post 11

Saturday, February 2 - 4:32pm

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http://eclectic.ss.uci.edu/ResFocusGrp/Graduate/GraduateProgram.pdf

Search on Wallace, or migrations. Dr. Wallace is widely considered the premier world expert on the genetics of the mitochondria, both in regard to the connection to various disease states, and also with regard to human migrations. As I recall, from a lecture he gave several years ago at UCI, he claimed that there had actually been, from the genetic evidence, three waves of migration to the American continent, not counting the recent European one.

Two of the waves, starting as early as 45,000 years ago, came by different routes via Asia and the arctic. The third wave, represented by the Great Lakes Indian tribes, especially, clearly came from Europe, about 13,000 years ago. Note that the members of these tribes look distinctly European, compared to the Western or especially Central/South American tribes. Note also that the Great Lakes tribes had much less difficulty in general than the Asian origin tribes in fitting into European culture and in many cases being thoroughly absorbed and treated as Europeans, whether from the effect of appearances, or from some combination with commonalities of culture (see below).

It's hard to imagine cultural artifacts lasting over ten thousand years, but it is intriguing to note that it was these tribes whose pre-Columbian constitution allegedly formed the basis for the U.S. Constitution.

http://publius.oxfordjournals.org/cgi/content/abstract/28/2/99

http://sidis.net/TSChap4.htm

I note also that, especially as compared to the Asian origin tribes, the North-Eastern tribes often had very sophisticated concepts of property, including land property, personal property, complex trade and land-use contracts and even intellectual property. The Ojibwa/Chippawa (who were an anarchist tribe, BTW) both had individual land property and also a complex market in ideas, dreams, stories, songs and magic spells. It has been noted that they also, of all the Indian tribes, had the least difficulty adopting and integrating into European culture.

(Edited by Phil Osborn on 2/02, 4:44pm)

Post 12

Saturday, February 2 - 7:57pm

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And this has what to do with a single genetic mutation of blue eyes, Phil?

We're talking about this sort of thing, not that.

Post 13

Sunday, February 3 - 10:32am

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and in case there is anyone interested there is now a patenity dna test kit available at rite aid and meijers. to see if those brown eyed parents with blue eyed kids are really honest people.

Post 14

Sunday, February 3 - 5:42pm

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Ed, is it possible that a mutation in different individuals could be genetically identical if it sprang up randomly in, say, two different people residing in different parts of the world? I don't think it would, I think there would be a difference in the mutation's sequence.

Teresa, the short answer is that anything's possible, but what you're describing is thoroughly unlikely. There's likely numerous possible ways to knock out the pigment in eyes and cause the underlying blue to show up. The chance that just one of these many possible extremely rare mutations occurred twice in an identical manner in the same place at about the same time thousands of years ago, and didn't occur since then, requires a huge suspension of disbelief.

Occam's Razor would indicate that the more likely scenario is that the mutation occurred once, didn't show up for several generations until, by random chance, it had become somewhat frequent enough in a small tribe that two individuals carrying the gene bred and produced an offspring with blue eyes (blue-eyed being a recessive gene, a copy from each parent is necessary for it to show up). A harmless rarity such as this would be attractive simply by its novelty. If blue eyes first occurred in a man, it could have spread very rapidly.

Imagine, for example, what would happen if a person was born with violet eyes. While some might be repulsed by its alienness, I imagine huge numbers of people would find this trait irresistable, sexually speaking. And as soon as it was expressed in a male, he would likely be impregnating women far and wide. The gene would thus spread until it became common enough that it was no longer rare enough to be valuable on the basis of novelty.

This sexual selection would be entirely aside from any adaptive benefits blue eyes might have in areas with less sunlight, similar to the adaptiveness of pale skin in such climes. Thus, once might expect that, given enough time, the gene would reach an equilibrium distribution, higher in high northern and southern latitudes, lower closer to the equator.