Every once in a while, I get an email from 23andme to notify me that I have a new DNA relative. When a new person gets their DNA sampled, and if they have given permission to do so, they send out a message to all the people who have some degree of genetic relationship. There’s a limit, obviously — we’re all related to everyone, so they don’t want to have to send out a notice to all of their subscribers every time someone signed up. It looks like the limit is somewhere around 4th cousins, which is already pretty tenuous. I have over 1500 DNA relatives flagged on the site, most around the 4th degree cousin level of relationship, which means that we share about 0.34% of the DNA inherited from our last common ancestor. I know hardly any of them.
When I look at the list, yeah, I definitely know the top 2 names — they’re my kids. 50% of our DNA shared. I don’t have to go at all far down the list before descending into total mystery. I recognize a couple of cousins, some familiar family names, and then…who are these people? Once you’ve dropped below 4% shared DNA, you’re too distantly related for me to have known you, with some exceptions, not that I would mind knowing you. I’m sure you’re all lovely people.
What I see from these kinds of data, though, is that genes are not at all a good measure of relatedness. Every child of each generation throws away half of one parents’ DNA, so generation after generation “your” genes are rapidly and progressively diluted, unavoidably. If you’re hoping for some kind of genetic immortality, it’s not going to happen, because the mechanics of meiosis are going to steadily break up the particular combination of genes that make up the genetic “you”. You can draw up all the pedigrees you want to illustrate your family connections, but they aren’t particularly meaningful.
As you can see, a fourth cousin would share a great-great-great grandparent with me, but that connection is rather abstract. I personally knew two of my great-grandparents, but anyone before that is, at best, an old black-and-white photo in a dusty family album, or perhaps a line in a census record. 23andme tells me that we have less than a percent of shared DNA passed down from that great-great-great grandparent. Lineage really doesn’t matter all that much, because we’re all just a great sloppy gemisch, a random subset of a population, and it’s the population as a whole that matters in the long run. The unique combination of genes that make up me are going to be broken up and dispersed over time, and some will be lost.
I can’t even stress enough how trivial those genetic inheritances are: I am not the sum of my individual genes, but the product of all of my genes interacting with each other and the environment in complex ways. My kids may each have 50% of my genes, but they are not 50% “me” — each one is unique and distinct, and I can have no claim on them. Part of the pleasures of parenting is creating someone new and watching them become independent and express themselves in ways you wouldn’t have thought of — not as a reflection of yourself, but as someone completely novel in all ways. They may share 50% of my genes, but they’re marshalling them in different ways in different contexts in cooperation with my wife’s genes.
I have no patience with possessive parents who want to mold their children to their preferences. I also don’t have much sympathy for “royal bloodlines” or other such nonsense. The king of England and I might both be related to William the Conqueror, but that drop of blood has been attenuated and reduced to meaninglessness by a thousand years of gene juggling and recombination and drift and mutation and loss. We shouldn’t care any more.
There is something meaningful there, though. I started this post by mentioning my email from 23andme — they had a new member who, they said, was my second cousin. I recognized the last name as belonging to one branch of my family, so I contacted my brother and sisters and asked if they knew who they were, because I sure didn’t. Yes, they did. It wasn’t my 2nd cousin, they were my first cousin twice removed; they were the grandchild of my first cousin. We shared 2.65% of our DNA with my grandparent, their great-great-grandparent, which, as I’ve said is a bit trivial and not at all grounds for showing up unannounced at their house for Sunday dinner. But we do have a connection.
I knew their grandfather well — he was my cousin, we regularly met throughout our childhood and youth to engage in shenanigans at their ranch in Eastern Washington. We hiked, we went fishing, I called him a stupid redneck, he called me a liberal pussy, and he beat me up now and then. It was a sometimes prickly relationship. He got wilder as he got older, while I became more staid, and we drifted apart, which meant fewer bruises for me but fewer wild adventures in the back country. You know, he once killed and ate raw a red-winged blackbird in front of me to prove he was tougher than I was? Kinda grossed me out.
Their great-grandmother, my cousin’s mother, was a rock who earned our respect. She was a tough old bird who raised a sometimes fractious family with love, despite often struggling economically. She was my father’s older sister, and I think she helped hold that family together, too. We visited her a few weeks before her death from liver cancer. She knew it was coming. She was awesomely brave about it all, retiring to a little house on the Palouse, where she could appreciate the country in her last days.
I knew their great-great-grandmother, my grandmother, even better. I spent many happy days in my childhood at her house, which was a crumbling shack next to the railroad tracks, with one wall slowly peeling away from the rest of the house and floors that sagged in odd ways. She had been a widow since about 1939, and raised a family of six kids single-handedly, working as a fruit-picker in season and in a cannery in the off-season. She was always kind and generous with her grandchildren, which was good since she had a great milling mob of them running wild over the house all the time. Sometimes my cousin would visit to twist my arm and make me say ‘uncle’ while I was there.
Those are the ties that bind, the connections that really matter. Native Americans have the right idea — you aren’t an Indian if you have a pedigree that shows some distant relative gave you a dollop of tribal DNA (Elizabeth Warren was taught that lesson a few years ago), what matters is the personal associations, the actual sharing of the life of an Indian. As a biologist, you’d think I’d place more weight on the numbers and percentages and genetics, but no, I’m not at all impressed with a 2.65% genetic share in my twice-removed first cousin’s DNA…but hey, I knew their grandfather, and that matters far more to me. I’d probably enjoy meeting them and having a conversation about family.
Unless they decided to beat me up to prove how tough they were. I would hope that doesn’t run in the family.