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There also wasn't much mixing of isolated populations of humans, leading to a relatively large amount of inbreeding. Sort of like a graph with clusters of heav

There also wasn't much mixing of isolated populations of humans, leading to a relatively large amount of inbreeding. Sort of like a graph with clusters of heavily linked nodes and only a few links between the clusters. https://www.newscientist.com/article/mg22029453-500-inbreeding-shaped-the-course-of-human-evolution/ https://www.newscientist.com/article/mg22029453-500-inbreedi... > "“In the distant past, human populations were probably only in the thousands or at best tens of thousands, and lived locally, exchanging mates only with their nearest neighbours.”" International shipping, and now, air travel, has changed this - the 20th century and the population boom have led to more genetic mixing than at any point in human history.

ch4s3 4y ago
We have pretty good evidence since 2013 of bands of neolithic humans moving over really tremendous distances. There's good evidence in the Americas of people moving from the Great Lakes down to the Gulf and beyond. Once horses were domesticated in Eurasia, all bets are off and we see mass migration from the steppe through to all of Europe, India, Iran, the Horn of Africa, and other places. This didn't happen in a single life time, but people on horseback with carts really got around.
- samatman 4y ago
  All of which is true, but Mark Anthony gets us well into the historical period. We have a pretty good sense from that of who did and who didn't get around. It's surely the case that the vast majority of Japanese on Hokkaido are not descendants of Mark Anthony. On Kyshu, maybe, the Portuguese contributed some genes there. We can really only be detailed about this with a Y chromosome for a man, or mitochondrial lineage for a woman, and that only covers the case of lineal descent. Not only can we not determine with confidence who is or isn't a descendent, even given a complete DNA sequence we don't have: most of those descendents won't have any Mark Anthony DNA at all! Chromosomes are more chopped than sifted, if that makes sense, I'm going on memory here, but somewhere around the 12th generation, we start having phantom ancestors: they existed, but left no record in our genes.
  - ch4s3 4y ago
    Yeah, of course the math makes sense but one can clearly find pockets of people it likely doesn't apply to. And for sure, trying to point to specific ancestors isn't really possible you don't even need to go back 12 generations in some cases if memory serves. My main point is that its becoming clear that many supposedly very isolated populations have in fact had gene mixture with outside groups in the not distant past and that there were large pre-modern migrations and mixing events.
    - saalweachter 4y ago
      If I'm recalling the numbers correctly, there's somewhere between a one in a million and one in a billion chance of not inheriting any DNA from one of your grandparents -- unlikely, but not so unlikely that there aren't dozens or hundreds of people walking around for whom that is true.
williamcotton 4y ago
My mother’s parents were from a small island community in Norway. They were second cousins. One time I got drunk and made out with my second cousin who still lives on that same island. My friends and family who witnessed the course of events were merely amused and not at all disgusted. Inbreeding ain’t going nowhere in coastal Norway! My (not at all previously related) wife thinks I’m insane that I love telling this story.
- PaulDavisThe1st 4y ago
  2nd cousin relationships are common in most parts of the world, and not viewed with the circumspection that 1st cousin relationships tend to be. You are much more genetically distant from a 2nd cousin than you are from a 1st.
  - Sunspark 4y ago
    I would say that the distance depends too on where someone is from. If they come from an endogamous community then they are related to other people in their tree through more than just a single branch. Islands, villages, etc. Sometimes it is fine, other times it can be a problem.
b06timmer 4y ago
While in the US Navy (1977 ~ 1981) I can distinctly remember the unique facial structures of the people in Southeast Asia and being able to tell what country they were from because of this. A couple of decades later with the mixing of populations by various means, and their diet changing in that-time frame, I couldn't reliably tell anymore.
irrational 4y ago
All it took was a single person who was a wanderer from each isolated community. I’ve read a number of articles that estimate, based on genetics, that every person living has a common ancestor who lived 2000-4000 years ago. It could have been a peasant in rural Tibet or a South Pacific Islander or someone(s) else entirely. https://sci-hub.st/10.1038/nature02842 https://sci-hub.st/10.1038/nature02842
xhevahir 4y ago
> There also wasn't much mixing of isolated populations of humans, leading to a relatively large amount of inbreeding. The genetics of Rome's population at the beginning of the Common Era were almost identical to that of Anatolia's, but just after Antony this began to change significantly due to the migrations that followed the Roman Empire's expansion: https://news.stanford.edu/2019/11/07/genetic-history-rome/ https://news.stanford.edu/2019/11/07/genetic-history-rome/

ch4s3 4y ago

We have pretty good evidence since 2013 of bands of neolithic humans moving over really tremendous distances. There's good evidence in the Americas of people moving from the Great Lakes down to the Gulf and beyond. Once horses were domesticated in Eurasia, all bets are off and we see mass migration from the steppe through to all of Europe, India, Iran, the Horn of Africa, and other places. This didn't happen in a single life time, but people on horseback with carts really got around.

samatman 4y ago
All of which is true, but Mark Anthony gets us well into the historical period. We have a pretty good sense from that of who did and who didn't get around. It's surely the case that the vast majority of Japanese on Hokkaido are not descendants of Mark Anthony. On Kyshu, maybe, the Portuguese contributed some genes there. We can really only be detailed about this with a Y chromosome for a man, or mitochondrial lineage for a woman, and that only covers the case of lineal descent. Not only can we not determine with confidence who is or isn't a descendent, even given a complete DNA sequence we don't have: most of those descendents won't have any Mark Anthony DNA at all! Chromosomes are more chopped than sifted, if that makes sense, I'm going on memory here, but somewhere around the 12th generation, we start having phantom ancestors: they existed, but left no record in our genes.
- ch4s3 4y ago
  Yeah, of course the math makes sense but one can clearly find pockets of people it likely doesn't apply to. And for sure, trying to point to specific ancestors isn't really possible you don't even need to go back 12 generations in some cases if memory serves. My main point is that its becoming clear that many supposedly very isolated populations have in fact had gene mixture with outside groups in the not distant past and that there were large pre-modern migrations and mixing events.
  - saalweachter 4y ago
    If I'm recalling the numbers correctly, there's somewhere between a one in a million and one in a billion chance of not inheriting any DNA from one of your grandparents -- unlikely, but not so unlikely that there aren't dozens or hundreds of people walking around for whom that is true.

williamcotton 4y ago

My mother’s parents were from a small island community in Norway. They were second cousins. One time I got drunk and made out with my second cousin who still lives on that same island. My friends and family who witnessed the course of events were merely amused and not at all disgusted. Inbreeding ain’t going nowhere in coastal Norway! My (not at all previously related) wife thinks I’m insane that I love telling this story.

PaulDavisThe1st 4y ago
2nd cousin relationships are common in most parts of the world, and not viewed with the circumspection that 1st cousin relationships tend to be. You are much more genetically distant from a 2nd cousin than you are from a 1st.
- Sunspark 4y ago
  I would say that the distance depends too on where someone is from. If they come from an endogamous community then they are related to other people in their tree through more than just a single branch. Islands, villages, etc. Sometimes it is fine, other times it can be a problem.

b06timmer 4y ago

While in the US Navy (1977 ~ 1981) I can distinctly remember the unique facial structures of the people in Southeast Asia and being able to tell what country they were from because of this. A couple of decades later with the mixing of populations by various means, and their diet changing in that-time frame, I couldn't reliably tell anymore.

irrational 4y ago

All it took was a single person who was a wanderer from each isolated community. I’ve read a number of articles that estimate, based on genetics, that every person living has a common ancestor who lived 2000-4000 years ago. It could have been a peasant in rural Tibet or a South Pacific Islander or someone(s) else entirely. https://sci-hub.st/10.1038/nature02842 https://sci-hub.st/10.1038/nature02842

xhevahir 4y ago

> There also wasn't much mixing of isolated populations of humans, leading to a relatively large amount of inbreeding. The genetics of Rome's population at the beginning of the Common Era were almost identical to that of Anatolia's, but just after Antony this began to change significantly due to the migrations that followed the Roman Empire's expansion: https://news.stanford.edu/2019/11/07/genetic-history-rome/ https://news.stanford.edu/2019/11/07/genetic-history-rome/