Monday, January 31, 2011

False family-history hopes

I find Australian friends on a few family-history blogs getting excited about DNA testing. Meanwhile, the great American science scholar and writer Carl Zimmer has just tweeted:

If I ever get a DNA ancestry test, I want @razibkhan to help me figure out what it all means:

If you take a look at Razib Khan's lengthy and complex analysis of his personal DNA results from 23andMe, you'll realize immediately that Carl Zimmer was being ironic in a friendly fashion. Often, naive newcomers to genealogical testing are awestruck by what the testing firms offer them. Certain testing firms lure their customers on by letting them believe that they're likely to come upon all kinds of cousins in the published databases. It goes without saying (as a little serious in-depth study of the subject, not to mention some basic arithmetic, would rapidly reveal) that these claims are surely exaggerated, to say the least.

All the inherited characteristics that make an individual what he or she is, today, come from a set of ancestors who were present on the planet Earth at various times over, say, the last couple of thousand years. That's already a lengthy time frame, and few of us have serious chances of finding out anything whatsoever concerning individual ancestors who lived, say, at the time of the Roman Empire. Not even kings and queens can obtain that kind of data! Moreover, you've been influenced genetically, during these two millennia, by a staggeringly vast horde of direct individual ancestors. (Do the arithmetic: 2 to the power of G, where G is the generation that interests you. Admittedly, there are countless repeated individuals in this crowd.) Consequently, the genetic input of any particular individual in this horde is like a drop of water in a wide and deep river.

In the domain of Y-chromosome or mtDNA haplogroups, the frame of reference extends back in an awesome exponential fashion over tens of thousands of years, giving rise to an ocean of population demography in which the very notion of your particular ancestors ceases to have any meaning whatsoever. And the particular individuals who provided you with the molecules that you might send off to get analyzed today were like a tiny line of bubbles rising to the surface of this vast ocean.

At a down-to-earth level, I've often said that DNA testing can possibly provide genuine assistance in the domain of genealogical research. In my personal case, for example, if ever I came across published Y-chromosome markers whose values matched mine, and if the individual in question happened to have an appreciable amount of traditional genealogical data about his background, then I might be able to learn more about my male ancestors named Skivington, Skevington or Skeffington. But those are two big "ifs". My results include values for 67 markers. Here's what I'm offered, today, when I look for matches:

Restricting my matching search to a maximum of little more than a third of my 67 tested markers, I find four individuals whose values are vaguely close to mine, with a difference (a so-called "genetic distance") of 3. Insofar as the values of a typical marker mutate extremely slowly (let's say, once every few centuries or so), it's most unlikely that any of those tested individuals named Walsh, Gifford, Davis and McGrath shared an even remote paternal ancestor with me since the end of prehistoric times. Consequently, it would be a pointless waste of time for me to attempt to contact such individuals in the hope of our sharing common family-history information.

So, you might say that my investment in Y-chromosome testing with FamilyTreeDNA was a little like buying a lottery ticket. And I haven't got anywhere near winning a prize yet.

ADDENDUM: Often, I imagine scenarios involving a near-perfect match between my 67 markers and those of another male, somewhere on the planet. The ideal scenario would involve an auburn-haired Frenchman named, say, Jacques Beaumont, living today in Normandy, who would go on to tell me, once we got into contact, that his family had a distant ancestor who went to England at the time of William the Conqueror. I would then be in a position to assume that the ancestor in question was no doubt the fellow who settled down in the Saxon village of Sceaftinga-tûn in the county that became known as Leicestershire. But there are countless other less perfect scenarios (where my use of the adjective "perfect" is deliberately tongue-in-cheekish). For example, once we move back to the 17th century, I no longer have any reasons to believe naively that all my direct male ancestors were indeed bona fide Skivington husbands. When I was an adolescent, the Aussie slang expression "ring-in" designated a substitute, somebody brought into a family context, often on false pretences. (I don't know the origins of this expression.) If, in a family, one of the offspring behaved quite differently to the other siblings, the child might be labeled a ring-in, indicating that the true identity of his/her father was not entirely guaranteed. So, it's quite possible that one of my ancestors was a non-Skivington ring-in who had succeeded in jumping into bed with the current Mrs Skivington and procreating the ancestral line that finally produced me. And we might imagine that this ring-in had a brother who was a seaman working on an old sailing-ship that once ventured out, say, to Batavia (modern Jakarta). While the vessel was picking up spices, the seaman might have picked up a young local lady and got her pregnant. If that were the case, then we could well expect that an Indonesian gentleman, today, has exactly the same Y-chromosome markers as I do. Moreover, there are 16th-century males in Turvey (Bedfordshire) referred to as Robert husbandman Skevington and George husband Skevington. Funnily enough, the term "husbandman" doesn't necessarily designate the chap who was legally married to Mrs Skevington. Etymologically, a husband was a fellow who tilled the soil. So the above-mentioned Robert and George might have been plowmen who worked as agricultural laborers on the Skevington estates in Turvey. In that case, genealogically, they would be ring-ins. So, anything's possible… even with perfectly matching Y-chromosome marker values. To borrow the title of a funny French movie, it would have been nice if the existence of our ancestors had always been like a long and tranquil river.


  1. Enjoyed reading your views on the subject.

    Three of my Aussie friends have recently had tests and I am thinking about it.

    I still think I'll go ahead as "You've got to be in it to win it."

  2. I agree entirely that DNA testing is a must. Some time ago, I even suggested that such a test should be envisaged as part of the baptismal rites (of a rationalist, rather than a religious, kind) for babies. The test is no more complicated than tracing a cross on the baby's forehead with so-called "holy water". Jewish parents, in particular, could have a simple saliva test carried out on their newborn boy instead of getting a silly old guy to attack the kid's prick with a knife.

    Concerning the choice of a DNA-testing company, I'm convinced you can do no better than Family Tree DNA. I would discourage people from dealing with the company mentioned by Shelley, because I disagree with some of the claims made in their marketing documents, and I would place no trust whatsoever in their curious devices designed to unearth the customer's various cousins, which are most unlikely to produce effective and useful family-history results.

    Then there's the all-important question of mastering the technicalities of the actual subject itself, which involves inevitably a basic knowledge of genetics and the analysis of human DNA. This is by far the greatest obstacle, because there are not many good books on the subject (which is quite new), and things are evolving constantly. When I first signed up for testing, my famous R1b1b2a1b5 haplogroup (which is commonplace today) had only recently been established!

    Finally, people need to be aware of the limits of the results of their DNA testing. If an individual learns that his/her markers are generally associated with Aborigines or Eskimos, say, this does not mean that the individual's overall genetic structure is that of a typical Aborigine or a typical Eskimo… for the obvious reason that your Y-chromosome or mtDNA sample reveals no more than the biological contribution of one single and narrow ancestral line in your genetic heritage.

    To my mind, by far the most exciting dimension of DNA testing is, not personal family history, but the vast study of the geographic origins of human populations, which I hinted at in an article entitled British tribes.

  3. I was interested in your comments too. As I said in response to your comment on one of my posts, I'm doing the testing as an experiment and an experience. I have also ordered a test at Family Tree DNA.

    While I'm sure that I could find a dozen relatives working on various branches of my family tree for a fraction of the time, effort and money of DNA testing there's a chance that taking a different approach could pay off. If not, well, it was fun trying.

  4. Shelley: The part of your comment that strikes me as fundamental is the final sentence, ending in "it was fun trying". Indeed, the kind of meditations induced by a personal experience in DNA testing are profound and intensely gratifying, particularly if you make an effort to come to grips with the technical aspects of the situation. For a male, or for the daughter of a male (which means everybody), it's utterly mind-blowing to realize that the basic data in that male's Y-chromosome has come down to him in an almost pristine form over countless millennia. We genealogists drive ourselves mad trying to unearth ancient documents, and then we're frustrated because we can't manage to read garbled words on the few documents we've discovered. Then, overnight, we've learned that each of us has a splendidly-unique personalized "road map" (that's not an ideal metaphor, but what the hell) right inside every one of the cells in our body. How's that for contemporary magic! Quite apart from the plausible but relatively dim hope of maybe coming upon another researcher with almost identical data, we can celebrate introspectively and narcissistically the existence of this "road map". For each of us, it is certainly the most precious thing in our personal existence, because it provides us with precise instructions for traveling (in a virtual sense) towards a fabulous destination: an objective awareness of my genetic identity. This data is a sacred endowment: the sort of thing that a believer might liken to a gift from God. OK, it's not exactly my complete individual genome, and the data from the genealogical test is unlikely to reveal anything at all about my personal psychology, intelligence and destiny. Needless to say, our DNA data is incapable of protecting us from everyday events such as grave health afflictions, warfare, accidents, floods, cyclones, pollution, etc. But it comforts us nevertheless, in the same way as a message from a loved one, even though the message might contain nothing in the way of useful information. The loved ones who have sent us the messages contained in our individual DNA are countless generations of ancestors, who gave us this gift in an act of love, but probably without ever imagining for an instant that we descendants might one day be capable of at least reading, if not understanding, it.