21 votes

You don't descend from all your ancestors

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  1. Atvelonis
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    I stumbled across this interesting video discussing the mathematics and biological mechanics of generational gene inheritance. The focus is on the probability of DNA connection to particular...

    I stumbled across this interesting video discussing the mathematics and biological mechanics of generational gene inheritance. The focus is on the probability of DNA connection to particular individuals over time. It has nice visuals and a clear presentation.

    I put this in ~science because it talks about biological genetics, but it belongs just as much in ~humanities or ~life because it influences the way we understand our history, both personal and cultural.

    Here’s a guiding question: “How does time interplay with socio-cultural, genealogical, and genetic inheritance in your family? In what ways do you experience connection (biological or otherwise) to your ancestors? How does that connection influence your life and personal values today?”

    This got me thinking about what parts of my family history I’m most attuned to.

    I can trace branches of my genealogy to at least the early 17th century, when my ancestors boarded the Mayflower to the New World. Other American lines go back similar distances and include early 18th-century Quakers, to many of whom my grandmother remains adamantly proud to be attached. I know my parents have visited old churchyards in Scotland and Greece and Germany and Norway where assorted distant relatives rested.

    The traditions I practice, the dances and songs and stories I know, the artifacts we’ve retained; the kind of subconscious interest I have in some kinds of art or music; it’s varied, but I certainly have preferences. There are definitely large parts of my genealogy I never touch, culturally, though I know they’re there. And others continue to have an outsized effect of my interests even though the genetic connection is minimal.

    I suppose the act of tracing out a genealogy creates a feeling of closeness which, from my understanding of the video, is much stronger than the literal biological connection one has with one’s ancestors at a certain point. That process of tracing the past centers it in the present in the context of modern sensibilities, which is an opportunity to interpret and reinterpret as appropriate.

    It’s an interesting coincidence in my case that the cultural “distance” I seem to feel from some of my ancestors corresponds approximately to my actual biological (individual) distance according to this video. From the chart around 5:00, meaningful distinctions between genealogical and genetic ancestry begin to appear after around 6–7 generations (~125–150 years). I think that’s the limit of what most people think of as their “family history.” I’m reminded of my grandmother (for example) telling stories her grandmother would tell about her (great-great grandmother’s) own childhood. I can feel a connection when I hear a story about growing up in that time, or of courtship during a snowstorm in 1875, and so on. But the living/oral history seems to drop off quickly past that point. Likewise, those ancestors from the 1600s I mentioned are at the very edge of having had any genetic influence on me at all. To be honest, the early 1600s is as far back as I care to relate—I can’t feel the stories in the same way.

    Of course not everyone can trace back their ancestors more than two or three generations—for any number of reasons. This is usually characterized as unfortunate, which it might be. However, the perspective such people have probably also enables totally revolutionary ways of thinking. Being rooted in the current moment or moments informed by the recent past—rather than in a family tree from 1620—focuses us on the experiences and problems that still matter today. Seeing history as living and continuous can give us great insight.

    5 votes