GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2007-09 > 1188769106


From: "Dora Smith" <>
Subject: Re: [DNA] Haplogroup I in Europe
Date: Sun, 2 Sep 2007 16:38:26 -0500
References: <c0b.1c930e06.3409e781@aol.com><11985d4c0708311503g540d92depc897022f3a7cdb21@mail.gmail.com>


A founder effect is when a single individual takes a genetic trait to a
small inbred group of people and his genetic traits subsequently become
common in the population the small inbred group belongs to. They often
belong to founding groups but not always. Sometimes a genetic trait they
carry was outright rare in the group they came from.

On the other hand, a single Dutch orphan carrying the still more rare
genetic condition variagate porphyria, went with a relatively small number
of other Dutch colonists to South Africa, and today an astounding 2% of the
population of South Africa has his mutation for variegate porphyria.

For instance, I think about 200 years ago (cannot verify online), an I think
Lutheran missionary went to definitely Lappland in northern Sweden, and he
carried acute intermittent porphyria, which is a very rare genetic disease.
Apparently he settled in an existing isolated village and had children.
His mutation subsequently became relatively common throughout northern
Sweden.

I think what you're describing is called something like a colonization
effect.

I once read in a Genetics text - no, don't ask me which one - that mass
migration is almost always genetically selective, which means that a
colonizing group doesn't just have less genetic variation than the
population it came from because of its smaller size. I honestly thought
that the Puritan migration to New England selected for genes for
temperament, but maybe it selected for historical population descriptors as
well.

Genetic drift is a more random process than what you've described - atleast,
the way I understand it.

I don't know if a 50% population reduction qualifies as a genetic
bottleneck; I think they reduce teh human population far more than that and
are always caused by very dramatic global ecological events, like the Tova
Volcano and the last ice age, that bring populations to the brink of
extinction. A true bottleneck leaves less than a few thousand of the
people it affects living. The effect isn't a dramatic population shift
toward Haplogroup H; it's a dramatic reduction in genetic variation such
that for instance instead of the many thousands of subclades H1 normally
has, all descendants from a particular point in time might belong to just a
few subclades. Then new genetic variation develops from those points in a
star-like pattern, where teh nodes mark genuine bottlenecks. Five to ten
genetic mutations back normally quite variable haplogroups seem to have been
reduced to just a few lines each. That wasn't any mere 50% reduction in
the population.

I've an idea that teh shift toward haplogroup H in Europe may best be called
"natural selection". It is beginning to look like it occurred quite
quickly since early medieval times.

Though I'm wondering how an 11,000 year old skeleton who was haplogroup H is
found in Somerset, England, and medieval excavations can't find any
haplogroup H. That should have been good for a founder effect. I'm
wondering if possibly we need to dig up more than a dozen cemeteries and
examine more than two people from each one.

Yours,
Dora Smith
Austin, TX


----- Original Message -----
From: "Rebekah Canada" <>
To: <>
Sent: Friday, August 31, 2007 5:03 PM
Subject: Re: [DNA] Haplogroup I in Europe


> Founder Effect:
> When a new population is formed by a subset of an older one. The new
> population may have only a fraction of the genetic variation of the
> old one. The term was coined by Mayr in 1963
>



--
Internal Virus Database is out-of-date.
Checked by AVG.
Version: 7.5.476 / Virus Database: 269.12.1/965 - Release Date: 8/21/2007 4:02 PM

This thread: