DNA Testing - Why Not

[CarolA3]

Guy probably didn't look at the 2011 date.
Guy may not have known that 'a poster' is now deceased.

 
Both facts are clearly displayed on the post in question.  How else would I know?

Yes, obviously we can all comment on anything that's ever been said by anyone anywhere.  I simply noticed that an argument was developing based on Guy's reaction to an old comment by the late Nick29, and to me that seems rather futile.

Carol

[Guy Etchells]

Guy probably didn't look at the 2011 date.
Guy may not have known that 'a poster' is now deceased.

 
Both facts are clearly displayed on the post in question.  How else would I know?

Yes, obviously we can all comment on anything that's ever been said by anyone anywhere.  I simply noticed that an argument was developing based on Guy's reaction to an old comment by the late Nick29, and to me that seems rather futile.

Carol

No I have not been on the various forums for a little while and was catching up.
I did not look at the date to the post I was responding to, but it was one which repeated the exaggerated claims made by DNA companies and those who think DNA is the best thing since sliced bread.

Let’s get some basic facts straight.
There is no DNA test that can prove the parentage of a child even if the parents and the child are available for DNA testing let alone the claims when only one party is available for testing.

DNA can show a possible parent/child link but cannot prove it, even the most accurate tests are at the most 97% accurate.
That believe it or not opens up the possibility of many different possibilities for parents let alone for grandparents etc. I cannot be bothered to check the exact figure but it is in the hundreds rather than single figures.

We are told that “AncestryDNA now have four million people in their database:”
Wow as many as 4 million, what does that mean, not much when you think that Brimingham here in the UK has a population of just over 1 million people.
That means AncestryDNA’s entire database is the size of four cities, hardly a huge database compared to the world population 7.347 Billion in 2015.
In fact if you look at it statistically any result is within the statistical margin of error, in other words any result could be true or false (virtually worthless, but don’t let that worry you as the paper trail is no more accurate either).

What is more worrying, and many people cannot grasp this, is that science is not based on facts, science is based on theories that stand until shown to be wrong.
The basic principal behind DNA is everyone’s DNA is different, that however is just a theory, it has not been proved it is not a fact and cannot be proven until everybody’s DNA has been tested and compared.

That may or may not be important, if it is proved that there is only a small duplication in DNA then in most cases DNA testing would still be a valid for of identification, if however as DNA testing becomes more commonplace it is shown that a person’s DNA is not unique an new theory will have to be forwarded.

DNA can be used as an additional tool but at present is about as accurate as the old IGI in genealogical terms.

Cheers
Guy

[CarolA3]

Thank you Guy.

If you're saying that the accuracy of DNA testing, for the purposes of individual family history, ranks somewhere between tarot cards and Pooh sticks, then I'm inclined to agree with you.

My views are of course subject to review as the science develops.

Carol

[shellyesq]

DNA can show a possible parent/child link but cannot prove it, even the most accurate tests are at the most 97% accurate.

Can you please provide a basis for such an exact statistic?  Does this refer specifically to genealogy-related testing or testing in general?  The US Department of State accepts DNA proof of parenthood that is accurate to 99.9% for purposes of citizenship, and I would think they'd be more inclined to want to prevent people from inappropriately becoming citizens than the reverse.  https://travel.state.gov/content/travel/en/legal-considerations/us-citizenship-laws-policies/citizenship-and-dna-testing.html

For those of us with no paper trail to use because of unknown parenthood, DNA is nothing short of miraculous.  I have matched with multiple members of my birth father's family, so it's hard to say that there's an error somewhere.  I find it rather disrespectful for people to compare it to superstitions.

[Guy Etchells]

DNA can show a possible parent/child link but cannot prove it, even the most accurate tests are at the most 97% accurate.

Can you please provide a basis for such an exact statistic?  Does this refer specifically to genealogy-related testing or testing in general?  The US Department of State accepts DNA proof of parenthood that is accurate to 99.9% for purposes of citizenship, and I would think they'd be more inclined to want to prevent people from inappropriately becoming citizens than the reverse.  https://travel.state.gov/content/travel/en/legal-considerations/us-citizenship-laws-policies/citizenship-and-dna-testing.html

For those of us with no paper trail to use because of unknown parenthood, DNA is nothing short of miraculous.  I have matched with multiple members of my birth father's family, so it's hard to say that there's an error somewhere.  I find it rather disrespectful for people to compare it to superstitions.

There are a number of studies which show that DNA testing is not 100%, in fact I have not seen one study that claims DNA can match 100%.
One study published by US National Library of Medicine National Institutes of Health looking at ERSA (estimation of recent shared ancestry) states “ERSA is accurate to within one degree of relationship for 97% of first-degree through fifth-degree relatives” (though this was quite an “old” study 2011).

I would not waste time looking at how DNA is accepted by courts or legal circles as the courts have presumed that a persons fingerprints don’t change for years and convicted people on this flawed evidence for years. The truth is two fingerprints of one finger taken after each other will differ in detail. The best that can be said is it is improbable that two people’s fingerprints will be the same, however winning the lottery is improbable but it is done every day.

There is a very basic but good article on some myths of DNA in the US family Tree Magazine online at
www.familytreemagazine.com/Article/DNA-Fact-or-Science-Fiction

It doesn’t use statistics but dispels the myths in laymans terms.
Cheers
Guy

[hurworth]

There are a number of studies which show that DNA testing is not 100%, in fact I have not seen one study that claims DNA can match 100%.
One study published by US National Library of Medicine National Institutes of Health looking at ERSA (estimation of recent shared ancestry) states “ERSA is accurate to within one degree of relationship for 97% of first-degree through fifth-degree relatives” (though this was quite an “old” study 2011).

I have not read this study, but I presume the title either accurately reflects what the paper is about or the peer reviewers and the journal editors did not notice the discrepancy.

The statement you quoted says that 97% of the time DNA estimated the relationship between two people to within one degree of the actual relationship and 3% of the time it didn't.  That is not saying that DNA testing is only 97% accurate.  It's saying that the estimated degree of relationship was within the defined parameters of the study 97% of the time.  For example if it estimated someone who was your 4th cousin to be in the range of 3rd to 5th cousin then this was "accurate" according to the terms of this study.

It's not as if the study found that 3% of the time DNA testing thought a person and a banana were 4th cousins.

In my own family we have some third cousins once removed (two pairs of siblings) that do not match.  Had they participated in this study they'd fall in the "inaccurate" 3%.  But the tests do not claim you will be a genetic match to ALL your 3rd cousins once removed as it is possible for cousins of this degree to have not inherited the same segments of DNA from the mutual ancestors.  As great-great or great-great-great grandchildren they would all have DNA from these mutual ancestors - just not the same segments as each other.

I don't expect DNA testing to be able to tell me how two people are related within one degree.  Infact I am surprised it is as high as within one degree 97% of the time.  This does not make the test worthless or hocus pocus.

There is plenty of information available on the ranges of DNA shared by various relatives and I understand that these are RANGES, hence why finding the actual degree of relationship is a multistep process which requires input from the customers.  This multistep process involves traditional genealogy, exchange of information and interpretation of results.  The company can not give you this on a plate. 

[Guy Etchells]

There are a number of studies which show that DNA testing is not 100%, in fact I have not seen one study that claims DNA can match 100%.
One study published by US National Library of Medicine National Institutes of Health looking at ERSA (estimation of recent shared ancestry) states “ERSA is accurate to within one degree of relationship for 97% of first-degree through fifth-degree relatives” (though this was quite an “old” study 2011).

I have not read this study, but I presume the title either accurately reflects what the paper is about or the peer reviewers and the journal editors did not notice the discrepancy.

The statement you quoted says that 97% of the time DNA estimated the relationship between two people to within one degree of the actual relationship and 3% of the time it didn't.  That is not saying that DNA testing is only 97% accurate.  It's saying that the estimated degree of relationship was within the defined parameters of the study 97% of the time.  For example if it estimated someone who was your 4th cousin to be in the range of 3rd to 5th cousin then this was "accurate" according to the terms of this study.

It's not as if the study found that 3% of the time DNA testing thought a person and a banana were 4th cousins.

First I did not give the title of the study I used my own words to suggest what the study was looking at and apologise if that confused you, but because of that you cannot presume anything.

That in itself invalidates any further comments you make as you have initially made a false assumption to support an invalid conclusion.

I cannot unfortunately continue this at present but will come back to this at a later date

Cheers
Guy 

[hurworth]

Alrighty, the world is flat and my 4th cousin is a banana.

[DevonCruwys]

Let’s get some basic facts straight.
There is no DNA test that can prove the parentage of a child even if the parents and the child are available for DNA testing let alone the claims when only one party is available for testing.

DNA can show a possible parent/child link but cannot prove it, even the most accurate tests are at the most 97% accurate.
That believe it or not opens up the possibility of many different possibilities for parents let alone for grandparents etc. I cannot be bothered to check the exact figure but it is in the hundreds rather than single figures.

We are told that “AncestryDNA now have four million people in their database:”
Wow as many as 4 million, what does that mean, not much when you think that Brimingham here in the UK has a population of just over 1 million people.
That means AncestryDNA’s entire database is the size of four cities, hardly a huge database compared to the world population 7.347 Billion in 2015.
In fact if you look at it statistically any result is within the statistical margin of error, in other words any result could be true or false (virtually worthless, but don’t let that worry you as the paper trail is no more accurate either).

What is more worrying, and many people cannot grasp this, is that science is not based on facts, science is based on theories that stand until shown to be wrong.
The basic principal behind DNA is everyone’s DNA is different, that however is just a theory, it has not been proved it is not a fact and cannot be proven until everybody’s DNA has been tested and compared.

Can I suggest you have a look at this short video from the University of Utah which explains how autosomal DNA is inherited:

http://learn.genetics.utah.edu/content/basics/molgen/

We inherit 50% of our DNA from each of our parents. You will share an entire Y-chromosome with your father. You will inherit mitochondrial DNA from your mother. Modern DNA tests using 700,000 or so markers can detect parent/child relationships unambiguously. The only other people on the planet with whom you would share 50% of your DNA are your siblings. Sibling relationships can be distinguished from parent/child relationships because you share fully identical regions with your siblings, whereas you inherit complete chromosomes from your parents. Please see the ISOGG Wiki page on autosomal DNA statistics:

https://isogg.org/wiki/Autosomal_DNA_statistics

If you read the ERSA paper that I cited you will see that you have misrepresented the conclusions of the paper.

Modern DNA tests can prove parent/child relationships and sibling relationships without ambiguity. Beyond parent/child and sibling relationships contextual evidence is required to determine the precise relationship. For example grandparents/grandchildren, aunt and uncles/nephews and nieces will share approximately 25% of their DNA but alternative relationships can usually be ruled out by looking at the age of the people testing. The Y-chromosome, the X-chromosome and mitochondrial DNA can also be used in combination with autosomal DNA to confirm the appropriate relationship.

You do not have to test the entire planet to prove close relationships. You will not share 50% of your DNA with anyone on the planet other than your parents or your siblings. There are now people who are finding through DNA testing that they have siblings that they knew nothing about.

It is also not necessary to test the entire planet to get useful results from DNA testing. We all have so many cousins and the databases are now at such a size that everyone is guaranteed to have plenty of DNA matches that they can work with. See the statistics here:

https://isogg.org/wiki/Cousin_statistics