DNA testing - genetic genealogy

[Tisy]

HI all,

I think geneticists are using an average of 31 years per generation at the moment (at least I think that is what I saw on my last foray into ftDNA's website).  This would make 217 years to our common 7 generation ancestor from 1963, i.e. 1756.

Cheers,

Tisy

[Nick29]

Yes, my calculations were a little bit out, but that does not disprove the point - even in 1756, there would not be enough people in the UK to support each of us alive today having 128 full blood ancestors, even taking siblings into account.  A large number of people in the UK have common ancestors.   As I've said so often in the past, DNA isn't very good at telling who your ancestors were, but it is very efficient at telling you who they were not.  Go back 10 generations, and you have 1024 full-blood ancestors to find.

[Tisy]

Hi all,

Here is David Faux's web page link -

http://www.davidkfaux.org/

Cheers,

Carol

[Nick29]

Sorry, not impressed.   David had traced his ancestry back to 1819 in the Shetland Islands, and then suddenly magically, we are back to the Vikings in 800 AD !     David is also quite fortunate to have one part of his ancestry spending a large amount of time in a place which was cut off from the rest of civilisation, and another part with an uncommon name with well-to-do links.  I wouldn't say that he was representative of the average person who is researching their family tree.

And, if the 'forensic users world - wide database' is only 100,000 people, when the current world population is just under 7,000,000,000, then it appears that only 0.0014% of the population is actually on the DNA database, and I suspect that most of those that are are on the N. American continent.  Now, I am neither a DNA expert, nor a mathematician, but I'm afraid that does not seem to give in the UK much of a chance of a good result, as far as I'm concerned.

[Tisy]

Hi Nick,

Why not put it to David himself?  His email address is on his site. 

Cheers,

Tisy

[Nick29]

Hi Nick,

Why not put it to David himself? His email address is on his site.

Cheers,

Tisy

Because 'David himself' is not pushing his website, or commenting here - you are 

And David has not jumped to any of the conclusions that you have appeared to jump to.

I was merely pointing out the mathmatics and science of DNA testing, in the hope that the promise of DNA genealogy will not instill false hope in people, in a process which does not come cheap.

[Redroger]

Nick, What I am certain of is this:2X GGF b1776 GGF b1798. Grandfather b1828, Father b1899, me b1940.
I did my best to bring down the age range, daughter b1966, son b1969, but back to form, grand-daughter b2007, to daughter, son, not yet married.First day of research in 1996 straight into IGI, still looking to get back beyond 2XGGF. Other lines are better though, on mother's side, 4XGGM b1803 approx, but this side has other problems, due to intermarrying, I have one 4XGGF who is also my 3XGGF. I think this makes me my own 4th cousin!

[Nick29]

Your grandfather was 71 when your father was born ?   Wow !   My dad was 50, and I thought that was old 

[Tisy]

Hi Nick,

I was not "pushing" David's site - I merely mentioned that he was researching U-152 and thought you might be interested - obviously not, as you has a five minute look and then did a hatchet job.  He has written many interesting papers, and of course he may not be 100% right about everything, but this is what good science is about - looking at something, having an idea about what it means, and then setting out to prove or disprove your hypothesis.

In the meantime I have now had a reply from Terry Barton of "Worldfamilies" with regard to Y-DNA matches -

"Hi Carol.  Yes - a match that is 63/67 or a genetic distance of 4 on 67
markers indicates shared ancestry.  I haven't looked at the calculations
lately - and there are a number of parameters that folks adjust in the
calculation - which change the outcome a bit -  but it seems reasonable that
7 or 8 generations is about the 50% probability for the number of
generations back to a most recent common ancestor (MRCA) in your situation.


However - it's very important that you realize that dna matching is not
precise in measuring generations.  The probability for shared ancestry in
this case ranges from a very few generations to something around 20
generations.  7/8 generations is simply the point where as many folks will
be more than 8 generations to MRCA as they will be less than 7

Now - the bit about 128 ancestors is totally irrelevant.  yDNA is very
specific - it is the y-chromosome - which is inherited from a man's father's
father's ... Father's paternal ancestry - that is being evaluated.  yDNA is
a very specific line of inheritance.

But - and this may be what your match is trying to say - you don't know
where that MRCA is on either your line or your match's line by the number of
differences.  You only know that at some point your two paternal lines
coincide into that MRCA.  It's now a paper trail exercise to find who is
your MRCA."

I am of course doing the paper trail and have already indexed more than 2,500 events for Wood/Woods and variants for the three counties which we are interested in, and will continue to look for the elusive ancestor.

Cheers,

Tisy