If you want to learn about your family tree, you're probably better off doing the work of compiling history than getting a $500 DNA test.

16 Responses to “Some kinds of DNA ancestry tests are basically astrology”

  1. eldritch says:

    DNA comparison can be useful for situations like identifying a certain corpse as being that of a certain European king, where the family tree is already well documented and traced and where the genetics of the living descendants are available for direct comparison.

    But sending off your own DNA to be analyzed to try and figure out your family tree from scratch? Useless.

    Why? Because DNA is really only a confirmation tool. You can’t extrapolate much about your ancestors from your own DNA alone. You can, of course, make some educated guesses about things like phenotype and ethnicity, as well as what region of the world your ancestors most likely came from, but beyond that, it’s up to historical investigation. An old photograph with a name and date written on the back can tell you far more about your family history than any isolated DNA test.

    • Boundegar says:

      Except when Great-Grampa flunks the paternity test.

    • Bionicrat says:

      “You can, of course, make some educated guesses about things like phenotype and ethnicity, as well as what region of the world your ancestors most likely came from”  Uhhh, yeah, but that’s STILL pretty cool.  I know Maggie says “Some kinds”  but I think many will take away from this posting of hers that genealogical DNA tests are a scam.  Finding out  that a heavy concentration of your DNA is shared with people from another continent from the rest of your family tree is pretty cool even if you have been completing your genealogy for decades. There’s always that mystery relative 125 years ago who was supposed to be “Portuguese” or “American Indian”  but probably was not.

      • belldl says:

        Exactly. My grandmother was adopted in around 1898. Forbidden topic, no records. No pictures from when she was young are around, an in her 70s+ when I knew her she could believably pass for several ethnicities, with darker features, eyes and high cheekbones. Did the DNA test on myself and have ruled out native american for sure, and mitochondrial dna tells me. . .ehh, “europe, maybe eastern”, which answers my question.

    • Jonathan Badger says:

      “Because DNA is really only a confirmation tool. You can’t extrapolate much about your ancestors from your own DNA alone”

      I’m pretty positive I know a *lot* about my ancestors from my DNA alone. I’m absolutely certain that I come from a metazoan lineage, for example. Molecular phylogeny is a wonderful thing. 

    • chgoliz says:

      “You can’t extrapolate much about your ancestors from your own DNA alone. You can, of course, make some educated guesses about things like phenotype and ethnicity, as well as what region of the world your ancestors most likely came from, but beyond that, it’s up to historical investigation. An old photograph with a name and date written on the back can tell you far more about your family history than any isolated DNA test.”

      Actually, it’s the opposite.  I can’t tell you the number of people who have come to me for help because DNA testing proved that their grandfather wasn’t biologically related to their father (or some similar situation).  All the paperwork is in place….everything looks perfect….but no, he’s not your daddy/grand-daddy.  People think this is a recent phenomenon, but I’ve helped in a number of cases where the NPE (non-parental event) was back in the 1800s.  It means everything on that branch of their family tree has to be cut out and re-done from scratch.

      Any genealogist worth their salt will tell you that every tree has its NPEs and other secrets.  DNA testing is much more accurate than paper records.

      • Antinous / Moderator says:

        Please, don’t fuel my fantasies.

        • chgoliz says:

           You’re really hoping to not be related to someone in your family tree?

          • Antinous / Moderator says:

            Now that there’s no one in my parent’s generation left alive, I’ve given up fantasizing that someone is going to tell me that I was adopted.

      • Adela Doiron says:

         Didn’t know there was an official term for my family’s long tradition of out of wedlock births.
        I have 2 family trees; one is the biological genealogy with it’s blank spots and the other is the social/legal genealogy.

  2. magscanner says:

    Not necessarily a scam, but not a trivial road to enlightenment, either. In the US the going rate is $99 or $129, and there are limits on what the data will tell you. It will certainly not tell you that you are descended from Richard the Third, but you and the others who share identified pieces of DNA in common may be able to find out who your most recent common common ancestor was. DNA can get you through “brick walls” where printed records are confused or lacking. Try 23andMe, FTDNA, or Ancestry.com DNA for legitimate analysis. BTW, there exist many open-source and free analysis tools, put together by a citizen-scientist culture of web-cognizant enthusiasts, who can take your raw data and find plenty of things the commercial operations are not yet capable of doing.

    • CH says:

      “but you and the others who share identified pieces of DNA in common may be able to find out who your most recent common common ancestor was.”
      In what way? I really don’t see how. Just because you share some DNA markers that does in no way mean that you are related. Or that you could identify who would be the common ancestor. Could you perhaps elaborate a bit how this could be done?

      To the original issue… I see this in the adoptive community, where parents get all excited because they have found a biological sibling for their child (with unknown biological parents). Well… probably not, unless it is an identical twin. What they get as a result is that the children are related with some probablility… but that is still not a yes/no, and without the biological parents’ DNA to match, there is absolutely no way that they could give anything else as a result. And add to this that the labs most probably don’t have any DNA samples from the area the children are from to build up a reliable database on how common different markers are in the area, even the given probability is pretty meaningless. But… people see the 90% probability they are related (which could mean second cousin, or just that they used very common markers for everybody from that area), or whatever they get from the lab, and read it as “Yes! We found a sibling!”.

      • chgoliz says:

        You’re talking about sibling tests.  They are a waste, that is true.  Autosomal testing is different.

        You are right that with the recent crop of international adoptees, there are many who come from countries where DNA testing is unheard of (especially via a USA-centered website) and so will not get as many matches.

        Here’s a recent Washington Post article which does not get into any technical details at all, but gives you an example of how even a young Vietnamese adoptee can learn valuable info from this testing:

        DNA Testing For Adopted Children.

  3. offalmangler says:

    I dunno…I don’t trust sites with pics of left-handed DNA. 

    lhdna,dr

  4. chgoliz says:

    Wow.  What a misleading article.

    There are different types of consumer DNA testing.  Sibling tests, for example, are a waste of time and money.  But autosomal DNA testing is actually quite good.  Lots of room for improvement, sure, but already rather miraculous.

    The currently accepted threshold between IBS (identical by state) and IBD (identical by descent) is around 7 cMs.  At that point, the statistical odds are extremely high that the segment match is due to a common ancestor and not just chance.  If you bump that up to about 15 cMs, you can be absolutely certain you’re dealing with a true “cousin” match.  Smaller segments can be useful for filling in the gaps when you have enough matches to triangulate your results.

    The better companies (23andMe, FamilyTreeDNA) provide a lot of info to explain how their testing matches you with others, and gives you your own raw data to download so that you can check it yourself (or give to someone else who has the computational power to do so).  Each generation out is less accurate, in that the computer algorithms will miss quite a few matches because the segments have broken down to less than 7 (or 5) cMs.  Doesn’t mean the two customers aren’t related IRL, just that they inherited such different segments from their MRCA (most recent common ancestor) that they have almost no genetic commonalities between them anymore.

    There are certain endogamous populations which have to be more conservative in interpreting their results because they are more inter-related than other groups.  This does not mean the results aren’t true, just that the MRCA might be a few generations further back than it seems by the level of segment matching.

    Ancestry has recently gotten into the consumer DNA testing game, and is still working out the details.  They state that they will release raw data to customers in future, but for now, you get nothing but their word about who you match.  And their ethnicity breakdown is wrong more than it is right.  They need to work a lot of kinks out before they can be considered in the same category as the above two companies.

    DNA testing is supported by old-fashioned paper trail genealogy to compliment and confirm.  Ultimately, it is breaking down a lot of brick walls in family trees, thanks to proving (or disproving) family lore and incomplete record-keeping.

    And yes, it is helping to find additional relatives that families didn’t know they had.

  5. timquinn says:

    I always keep a sample with me. just in case.

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