Are we related to people born before 1575?



Babbitt Family Tree
Originally uploaded by FrodoBabbs

While sampling some nice beer in Århus earlier this year with my good old friend Thomas Mailund, we had an interesting discussion about how long our genes live on for.

I was reminded of this discussion when I managed to find my great-great-great-great-great-great-great-great-great-great-great-grandfather on Google. His name was Georg Widmann, and he was born around 1532 in Heiningen in Württemberg.

However, as I discussed a few years ago, we get half our genes from our father and the other half from our mother; we therefore get 25% from each grandparent, 12.5% from each great-grandparent, etc., so when do we reach a point when there’s nothing left?

According to Wikipedia, the “haploid human genome contains ca. 23,000 protein-coding genes”. 23,000 can be halved 14.49 times, which equals around 435 years (at a generation length of 30), and this means that any ancestor born before the year 1575 is likely to have contributed less than one gene to our genome. (Georg is of course an exception – ignoring the possibility of adultery and mutations, my Y chromosome is an exact copy of his.)

One can look at the numbers differently, too. Genes are defined by the “2.9 billion base pairs of the haploid human genome”. 2,900,000,000 can be halved 31.43 times, taking us back 943 years to the year 1157, but that will include ancestors who have only contributed junk DNA.

The “human genome contains vast regions of DNA the function of which, if any, remains unknown. These regions in fact comprise the vast majority, by some estimates 97%, of the human genome size.” 3% of 2.9 billion base pairs is 87 million base pairs, which would take us back 791 years to the year 1219.

However, the “nucleotide diversity between humans is about 0.1%, which is 1 difference per 1,000 base pairs.” That would take us down to 87,000 base pairs that actually matter, and that number can be halved 16.41 times, which would take us back 492 years to the year 1608.

To conclude, I’m not absolutely sure what the cut-off point should be. There’s definitely no point in doing genealogy further back than the year 1157 (except for pure patrilineal and matrilineal descent), but there are good arguments also for stopping in 1219, 1575 or 1608.

9 thoughts on “Are we related to people born before 1575?”

  1. Another cutoff is the generation, where the number of ancestors are greater than the population at that time. I’m pretty sure that the total human population in 1157 were less than 2^31 (~2 billion), so you are clearly a result of inbreeding. Given the lower mobility, even a few decades ago, the uppper bound for meaningfull ancestry tracing is very likely going to be a lot lower.

    In fact, I think you can trace several lines back to Georg Widmann, if you look hard enough.

  2. I guess the point is lineage rather than genetic connection, and that’s really only relevant if there’s something significant being handed down the line, like a crown or something. Also, even in royal lineages, there have been doubts about the genetic link between a father and son, to put it delicately. There are even doubts about Prince Andrew’s genetic lineage!
    I think the interesting thing is not the individuals in the family tree that far back (unless there is something unusual about them) but the origin of the family and family name.
    My family name came from Escoville in Normandy. As the Normans were once Norsemen, I guess there’s a link with you. Ah, but your Georg is German, so obviously not … maybe you’re Saxon. I’m from an adopted line though and we suspect there’s Ashkenazi blood there.
    It would be very funny if you turned out to be more genetically English than me, with your Saxon ancestor!

  3. @Anders, you’re right, of course. Given that my family seems to have lived in Heiningen (a village of 1000 inhabitants at the time) for at least 250 years, it would be very surprising if they didn’t intermarry heavily.
    Actually, I guess it would make sense for many people to say that they’re descendants of villages, rather than people. In my case, you could argue that I trace my ancestry to the villages Heiningen and Schura in Germany and Knebel and Tved in Denmark.
    @Rob, I suspect there’s plenty of Celtic blood in my German family, and the Germanic ancestry is probably from the Suebi rather than the Saxones.

  4. The point about the Y chromosome is interesting – it means that, chromosomically, it makes much more sense to look at paternal lineage than maternal. Maybe they were on to something when they started on that?

    And remember, it takes a village to raise a child.

  5. Greetings Thomas. We may be related, though prior to 1575. The ancestor I can trace direct lineage to is Lienhard Widmann (b. 1606) of Aidlingen/Ehningen, Wurttemberg and perhaps to an illegitimate son of the local warlord and a serving girl, one Mangolt of Dagersheim (b.circa 1490). (Worldroots.com/brigitte/widm.htm).
    I have had my DNA tested by Family Tree DNA and therein lies quite a story. FT DNA claims my bloodline goes back to Egypt (North of Lake Chad) 18,500 years ago and is most predominant today in Somalia and across N.Africa and is today an 8% minority in Germany. I realize this may be something of a bolt from the blue but look forward to discussing it further with you, cousin, if I may call you that. Robert, NYC

  6. @Cousin Robert, it’s a pleasure to hear from you after all those years! I’m sure our most recent common ancestor wouldn’t have imagined his descendants would one day get in touch like this! 🙂
    It’s intriguing to hear the results of your DNA testing. I’d love to get mine tested, too. Do you know what your DNA strand is called?

  7. Hello Thomas –
    I don’t want to use up your very excellent blog space with a matter that interests only you and I, but to answer your question I have tested for E 1b1b 1a2 with an assumed (e=V13) out to the 24 haplogroup level and have discovered some probable relatives here in the USA named Weedman. Wikipedia has info on the above haplogroup as do several other sites. I have worked up a tenative history of the Widmann name – 300 words or so. If interested, I will send this either to the Blog or to an off-blog address. Otherwise, congratulations on your Blog. It is very wise and you have attracted many bright, perceptive people to it – thought and learning being goals of the Widmanns I tend to believe.

  8. @Robert, fascinating, the Wikipedia article about E1b1b1a2 is here.
    Feel free to send your Widmann name history to the blog, but alternative send it directly to me (twid at bibulus dot org).

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