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When Did Americans Stop Marrying Cousins? Ask the World’s Largest Family Tree
- Retric 9y agoI have some doubt that the generations are that cleanly separated when doing genealogy. The if nothing else the youngest and oldest children of a couple can be 20+ years apart. The same person could easily show up as someones great grandparent (3) and their great great grandparent (4).
- ajmurmann 9y agoIn high school I sometimes hung out with a friend and his uncle. The uncle was two years younger than us.
- mikestew 9y agoI have an aunt that’s two weeks younger than I. Another aunt from that same mother is only six or seven years older than I. The fact that my Mom got started young with me is a contributing factor.
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- batbomb 9y agoIn high school I hung out with a lot of such people, but I went to high school in Utah. My best friend had 11 sisters and 3 brothers.
- smellyindian 9y agoIndian family trees in certain communities are like this. And in general, due to keeping in touch, or remaining in one particular geographic area, one hears stories like this quite commonly in India.
- maxerickson 9y agoAre you talking about the graphic? I would guess they imposed some order on it, but I also sort of expect that the sort of thing you talk about doesn't happen all that frequently in different branches of a family tree.
- cgriswald 9y ago> if nothing else the youngest and oldest children of a couple can be 20+ years apart. This isn't relevant to generations. My youngest sister is 21 years younger than I am. But we are both part of the same familial generation. My children and her children will also be part of the same familial generation. (This is irrespective of the fact that my sister is a millennial and I am not.) > The same person could easily show up as someones great grandparent (3) and their great great grandparent (4). In the case of the graphic, I suggest that they put each person at the highest possible place in the hierarchy and then simply extended the relationship line down in cases like this.
- Retric 9y agoNow fast forward 200 years and that clean separation you describe starts looking like a tangle as you and your sister marry people from different 'generations'. Basically, if you want to understand how people actually behave you need to exclude the living as their relationships are going to be more complex than such neat abstractions suggest. It's only with dead people that you can really understand their life story after-all someone can get married at 25 and again at 95.
- totalZero 9y agoWhat is your definition of "generation," and why do you refer to it as an abstraction? We are referring to generations as a structural parent-child term, where people on the same tier of the tree share the same generation. This is not the same as saying "Generation X/Y/Z" and so forth, which is a different meaning of the word entirely.
- Retric 9y agoI am deriving the second definition from the first. Basically, as you start looking at the family tree that actually represents humanity the idea of generation breaks down, do you mean the shortest route from you to someone in ~100,000 BCE or the longest route to some person in ~100,000 BCE. You could say your mother's mother's mother's ... or your father's father's father's but even then the length of the chain going back that far stops being equivalent. The only thing that becomes meaningful on such a scale is simply generation as unit's of time.
- epistasis 9y agoNo need to doubt the visualization, rare cases like that blend into the visual noise. And in fact, in the most ancient generations, where this problem would be more prominent, you can see far less delineation of the generations. They can cluster the individuals (green) into hierarchical circles cleanly, then add a line that jumps over one generation, which would not be visible at the resolution of the plot.
- kbutler 9y agoZoom in. You can see marriages (red dots) in the middle of green clusters. They've just done some graph layout to make it look nice.
- bdcravens 9y agoIndeed. My wife and I are 40 and 41 respectively and are pursuing our first child via IVF. Meanwhile, some of her cohorts are now grandparents.
- GreeniFi 9y agoA friend reported going to the wedding of German first cousins who married. The groom opened his speech with, "just in case you're still wondering, yes it's legal". No, they were not the British royal family. And apparently it was quite an uncomfortable moment. I relate the story as something which would have been quite normal once, whilst legal now, is fairly taboo. I'm not sure why, although obviously feel and appreciate the taboo.
- JumpCrisscross 9y ago> I'm not sure why Taboo because we discovered heredity. Legal because this isn’t prevalent enough to merit national attention.
- alphaalpha101 9y agoHaving children with a sibling isn't anywhere near as dangerous as people think it is. People seem to think it nearly guarantees birth defects. It really doesn't. Cousins are even less dangerous.
- da_chicken 9y agoNo, we've understood heredity for a very long time, and sex between siblings or between parents and children has always been a taboo. Cousin marriage, however, is not particularly harmful (https://www.psychologytoday.com/blog/animals-and-us/201210/the-problem-incest https://www.psychologytoday.com/blog/animals-and-us/201210/t...). The real reason we stopped marrying cousins is: 1. We started to live in large cities instead of on farms and ranches. (https://www.census.gov/population/censusdata/table-4.pdf https://www.census.gov/population/censusdata/table-4.pdf) 2. We could reasonably travel more than 10 miles from home in a day. In other words, we used to marry cousins because it was too difficult to find better prospects.
- rflrob 9y agoI haven’t yet read the scientific article that it’s based on, but the OP points out that there’s about a 50 year lag between the move to cities and a decrease in cousin marriage, so there was probably some cultural component.
- epx 9y agoMy grandpa married his second cousin, it was already frowned upon in 1935 but not unheard of. One improvement factor was transportation - the bicycle was invented not much before, and it was expensive. But a bike or a train ticket allowed you to know people beyond the rural village you lived. It's been even said that the inventor of the bicycle was the 2nd greatest feminist, because he improved the availability of suitable grooms, nobody needed to marry the violent moron next plantation anymore.
- hackerbrother 9y agoIs there a known "greatest feminist"?
- epx 9y agoThe one who invented the washing machine.
- subpixel 9y agoThis is probably more true than many realize. There’s a great history re-enactment series on BBC called Victorian Farm, Edwardian Farm, etc (I believe they’ve done more) and before technological innovations laundry was the largest time-sink in a woman’s life. Watching the labor involved was a horrible revelation for me.
- meric 9y agoWhy is it horrible? Their work was valuable at the time. It’s only horrible if we choose to not see the value they provided; IMO It’s not any more or less horrible than the husbands whose largest time sink was deep in the coal mines or on the streets sweeping horse manure. I don’t know about you, I’d be annoyed at someone feeling bad for me having to do my work. I’m grateful for our ancestors putting whatever effort necessary to keep society going.
- mc32 9y ago
- xchip 9y agoTL;DR: It wasn’t until after 1875 that partners started to become less and less related.
- Gibbon1 9y agoReminds me of something I read about that in the 1970's. Mostly people married someone born 10 miles from them. Suddenly steam ships and railroads came.
- slavik81 9y agoThe Economist had a special report on marriage a few months back with a bit on cousin marriage around the world. They had an interesting conclusion. > Two academics, Bilal Barakat and Stuart Gietel-Basten, point out that when women usually have five surviving children, a woman can expect to have 25 male cousins. When the average number of children falls to two, that same woman will have just three male cousins, some or all of whom might be younger than she is, and thus ineligible as marriage partners. The marriage squeeze will be even tighter in cultures that insist, for example, that a woman marry not any old cousin but her father’s brother’s son. Eventually, cousin marriage will be crushed not by medics but by mathematics https://www.economist.com/news/special-report/21731490-practice-cousin-marriage-doomed-consanguineous-marriages-are-declining https://www.economist.com/news/special-report/21731490-pract...
- dalbasal 9y agoInteresting! I'd never thought of cousin availability as a factor. But....is it actually possible to average much over 2 children for very long? I mean, that's a population boom.
- jhbadger 9y agoDefinitely yes. Pretty much the case throughout most human history. Somewhat countered by the high rate of infant/children death though.
- Gibbon1 9y agoWeird things happen because the the number of surviving children isn't uniform. Where that hit home for me was during the great depression the median family was small. Most families were using various types of birth control and illicit abortions were rampant. However most children came from larger families... because large families were really large. And poor. Hint my dad had two brothers. One of my dad's brothers fathered six kids. My dad three and his other brother one. So families sizes of 6:3:1 The majority of my grandmothers grandchildren came from a family with 6 children. Those six have 14 children. My dad and other uncle have two grandchildren total, one each.
- iguy 9y agoThere's a much bigger and longer story than this. Roughly speaking, it's my understanding that the catholic church suppressed this in Europe from roughly 1000 years ago, essentially as a way to counter alternative power centres. Here's a famous article about Iraq, where this did not happen: http://www.theamericanconservative.com/articles/cousin-marriage-conundrum/ http://www.theamericanconservative.com/articles/cousin-marri... Here's a discussion of a recent paper: http://marginalrevolution.com/marginalrevolution/2018/01/marrying-cousin-bad-democracy.html http://marginalrevolution.com/marginalrevolution/2018/01/mar...
- narrator 9y agoI think that someone could write a very reasonable sounding evolutionary psychology article about why the guiding hand of natural selection intervened and stopped cousin marriage due to higher rates of genetic abnormalities. However, in this case they'd be wrong in that the Catholic Church intervened directly and conciously and put a stop to cousin marriage. Finding out that a phenomenon is not due to evolutionary psychology requires careful historical research and that's hard work. Making up evolutionary psychology ideas though takes no time and can make for a great clickbait article.
- iguy 9y agoIt seems clear evolution has uniformly negative opinions of brother-sister couples. But cousins are more interesting, because the biological downside of having some ill (or just thick) grandkids must be balanced against the upside of having a tight clan, without divided allegiances, to fight off other clans.
- jrmarc 9y agoWhile isolated instances of first cousin marriage aren't especially harmful, contrary to what some comments here suggest, if done across successive generations, these unions can produce a catastrophic unmasking of harmful recessive alleles, and the nations with the highest rates of consanguineous marriages also often have the highest rates of birth defects (see p. 22): https://www.marchofdimes.org/materials/global-report-on-birth-defects-the-hidden-toll-of-dying-and-disabled-children-full-report.pdf https://www.marchofdimes.org/materials/global-report-on-birt... However, while the dangers of inbreeding depression are common knowledge, it's worth pointing out that outbreeding depression exists as well. Where lies the ideal balance between these two extremes? Surprisingly, it appears to be marriages between third or fourth cousins, if you use fecundity as a proxy for general offspring health: https://www.sciencedaily.com/releases/2008/02/080207140855.htm https://www.sciencedaily.com/releases/2008/02/080207140855.h... A third or fourth cousin is a person with whom you share first cousin grandparents or great grandparents--essentially a distant relative, or simply put, someone of your own "race," which is quite at odds with the "hybrid vigor" claims often made to tout interracial marriage. Apparently just marrying any old white person (if you're white) gives you all the hybrid vigor your offspring need.
- touringcomplete 9y agoIt was the invention of the automobile that made it possible to stop marrying cousins.