Ancestry and Genetics

 This is adapted from a post I made to an anti-racism server earlier. I thought since it was so long, might as well turn it into a blog post!

Hey so while we’re on the subject of ancestry, thought I’d share some thoughts that I have from a genetics perspective since that’s what I study and I have many thoughts on this. Please let me know if anything’s confusing, since I also want to teach genetics so figured this’d be good practice for me. Sorry in advance for the essay!

Ok so ancestry can be important to you culturally or personally, I’m not trying to discredit any of that. But from a genetics perspective? A lot of it is nonsense. And a lot of this gets co-opted by white supremacists, so I think it’s really important to understand the science of what’s actually going on here.

Biologically, each person comes from two parents that you share a (random) half of your DNA with. (Doesn’t have to mean that these people are in your life or anything, but you have 2 parental slots in your ancestry.) Go back another generation you have 4 grandparents, 8 great-grandparents, and so on. If we assume each generation is 25-30 years and each generation doubles in size, 500 years ago you had 1,048,576 ancestors. A thousand years ago you had 1,099,511,627,776 ancestors, which is now more people than have ever existed! (I think best estimate is 107 billion people have ever existed, might be slightly out of date on that though.) Basically the solution to this paradox is that some people occupy multiple positions on the family tree, and that there is overlap in everyone’s family trees. If you do the math, anyone with European ancestry shares one common ancestor from the 10^th century in Europe. And this is nuts, this isn’t how we typically think about ancestry. We think that we come from a distinct line, when in reality my ancestors are also your ancestors. We are all much more alike (genetically) than we think, the differences between individual people make up less than 0.1% of the genome. 

This also makes sense from a historical standpoint: people move around, borders aren’t static. People go places and have kids and move around in relatively short periods of time. Insisting that you come exclusively from one village means that you’re ignoring a whole lot of your family history (could be lost or just uninteresting). It also means that you’d be dangerously inbred if that were true. Sidenote on that: you get 2 copies of each gene, one from each parent. Your genes are actually happier with 2 different copies than with 2 of the same copy. Since we all share 99.9% of our DNA our bodies can handle a certain amount of sameness, we are all inbred to some extent (fun stuff!), but when everything is the same is when there’s a problem.

Let’s take my family as an example. (Take all this with a grain of salt, I’m only one person and not representative of a lot of other people and I’m very privileged in many ways here.) I’m Italian American, and honestly I’m proud of it, growing up Italian American has had a big impact on my life. My family is so Italian we once put in a bulk order for shirts that say “Legalize Marinara” because everyone wanted one. I don’t know very much about my family tree (mostly because that never interested me, I think my mom put in some work to develop one though) but let’s look back at what I know. My parents both grew up in New York City, my grandparents were kids when they immigrated to the US from Italy just before the Great Depression (early 1900s). My great-grandparents (8 of them remember) we’ve traced back to a few cities in southern Italy. My great-great-grandparents (16 in total) I have no idea where they’re from, probably some of them lived in Italy, but I’m willing to bet a good chunk of them lived in various places around the Mediterranean. Italy wasn’t even unified until 1871 (and some areas didn’t join until after, but this initial time is right about the time of my great-great-grandparents) and before that it was different territories with different governments. So why do those borders not matter when considering ancestry? Why do I give a full stop at the modern Italy borders? And if you go back farther, my great-great-great-grandparents (32) probably came from all over Europe and the Mediterranean!

Even looking culturally, it doesn’t say much about me. When my family immigrated, it was the heyday of discriminating against Italians (this is not the case anymore, Italians are white). There were lots of traditions they stopped under the pressure of assimilation. I have a great-grandparent who went to Sing Sing prison for demanding fair wages for being Italian, and when he didn’t get that, he burned down the overseer’s house. (I only mention this because THAT’S COOL AS FUCK it’s one of my favorite family stories.) It even affected my parents to a certain extent, my dad was sent home from elementary school with a note saying that he had to stop speaking with an Italian accent. Really most of the traditions we have come from my parents growing up in an Italian American enclave in New York City. Great example of this is that we used to have a pasta course during Thanksgiving dinner (very Italian American given that Italians don’t celebrate American Thanksgiving). We don’t do this anymore because it’s just too much food. So we’re even losing those traditions since culture is constantly evolving. If I have kids, they likely will just be raised with American traditions, maybe with a side of marinara sauce.

Alright so given alllllll of that, what do I even mean when I say that I’m “proud to be Italian”? I’m not even sure, it can feel a lot like I picked a random aspect of my upbringing to hang 90% of my personality on. But I think it also means that I want to feel connected to my family, and to our specific traditions. And there’s nothing wrong with that, but it can often be used in a way to imply things that simply aren’t true.

Apologies again for the essay, but let me know if anything’s unclear. I can also dig up sources for further information if you’d like, but I’d highly recommend the book How to Argue with a Racist: What Our Genes Do (And Don’t) Say About Human Difference by Adam Rutherford since he talks about this and other genetics ideas embedded in racist arguments.