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From: "Ken Nordtvedt" <>
Subject: Re: [DNA] Brown eyes
Date: Mon, 8 May 2006 23:36:34 -0600
References: <3fb.1bce527.31916eaf@aol.com>


----- Original Message -----
From: <>
To: <>
Sent: Monday, May 08, 2006 10:03 PM
Subject: Re: [DNA] Brown eyes


> In a message dated 05/08/06 1:45:25 PM Pacific Daylight Time,
> writes:
>
>> I am not interested in prolonging these word games; there would be a
>> practical application I am interested in in population studies (and
>> potentially rate of selection against the brown gene) if the data of
>> brown
>> eye percentages by regional populations (much like the existing blood
>> group
>> data) exists, but so far that has eluded searches and perhaps does not
>> exist.
>
> If you're interested in natural (or sexual) selection, which acts on the
> phenotype, not the genotype, why does it matter so much to you that there
> be just
> one allele for one gene that results in brown eye color? Selection acts on
> many multi-factorial traits.
>
> Anyway, I checked Cavalli-Sforza's "History and Geography of Human Genes."
> He
> covers eye color briefly, but he does include a map taken from Carleton
> Stevens Coon "The Races of Europe" for hair / eye color combined (in
> quintiles of
> light to dark). The general impression is clines with a few localized
> "islands"
> that darker or lighter than their surrounding neighbors. I have the big
> hard-cover edition, but I think the paperback version would have the same
> text and
> pictures (pp 266-267 if someone wants to check for Ken).

> Ann Turner

It matters not to me how many alleles are participating to various degrees
in the brown dominance. It's sort of like the issue of DYS464; there are a
number of interesting different things going on in the mutations of this 4
copy marker. If one knows or finds the rules of the mutations, the marker
can be used for purposes of population studies, without fully understanding
the different underlying mechanisms of change in the STR lengths, as
interesting as learning the underlying mechanisms will also be.

All I need are that the final rules of inheritance for a digitized phenotype
dichotomy (brown versus non-brown eyes) 1) work most of the time, and 2)
the two defined phenotypes can correctly be sorted most of the time.
Population studies can survive small enough error rates.

I will outline the problem which intrigues me but apparently no one else, as
I have tried to discuss it a number of times previously on the list, and the
subject always gets diverted to something else.

If the areas of Europe with very high frequency of blue eyes today had been
populated by just one immigration of people who had overwhelmingly converted
to blue in the early days of the group's existence, I could consider that an
accident and perhaps a sufficient explanation for what is seen today. But
these areas of Europe are believed to have had major and separate
immigrations of several male haplogroup populations --- R1b, I1a, R1a, N3
..... Did all four of these population movements bring predominately
non-brown genes into the area? I think this gets too improbable. So
selection had to sweep almost all the brown genes out of the populations in
a rather short time, given the dominance of brown genes, yet we see very low
frequency of brown eyes over vast sweeps of Europe (from Ireland to Russia)
populated by multiple flows of immigrants. I am sceptical of such rapid
selection, but maybe in the end that will have to be the explanation of what
is seen. Some of the mixings of these populations in Europe are only
several thousand years old.

Someone did send me some maps like you mentioned concerning Norway and
surrounding areas. I don't know if they were from Coons' book? I can't
read the Norwegian too well, but I think they combine eye and hair coloring
as a single variable which makes things a bit messy; there are populations
of dark hair but non-brown eyes in parts of Europe.

But the maps of Norway do show some regional clines which tantalizingly seem
to correlate with some apparent regional differences in R1b, I1a, R1a
breakdowns of the Norwegian regional populations. What I think is needed
for starters is a good census by region in Europe of the frequency of brown
eyes --- to then be cross-correlated with the frequencies of the different
yhaplogroups in the regions. I'd suggest a similar examination of the mtdna
frequencies, but I have the impression the clines and pockets of frequency
variations are not as strong in the mtdna as there are in the ydna?

The first time I had a glimpse of this issue I asked myself, "what was the
frequency of brown eyes among the I1a when they started to go north after
the last glacial maximum --- given that I1a are predominately non-brown eyed
today?" And of course the issue got broadened rather quickly after looking
around Europe.

Ken



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