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While this article's content isn't exactly wrong, the Wikipedia on "Identical ancestors point" gives some important context for what's actually being asserted:

by themgt 6y ago

While this article's content isn't exactly wrong, the Wikipedia on "Identical ancestors point" gives some important context for what's actually being asserted: All living people share exactly the same set of ancestors from this point back, all the way to the very first single-celled organism. However, people will vary widely in how much ancestry and genes they inherit from each ancestor, which will cause them to have very different genotypes and phenotypes. This is illustrated in the 2003 simulation as follows: Considering the ancestral populations alive at 5000 BC, close to the ACA point, a modern day Japanese person will get 88.4% of his ancestry from Japan, and most of the remainder from China or Korea, with only 0.00049% traced to Norway; conversely, a modern-day Norwegian will get over 92% of his ancestry from Norway (or over 96% from Scandinavia) and only 0.00044% from Japan. Thus, even though the Norwegian and Japanese person share the same set of ancestors, these ancestors appear in their family tree in dramatically different proportions. A Japanese person in 5000 BC with present-day descendants will likely appear trillions of times in a modern day Japanese person's family tree, but might appear only one time in a Norwegian person's family tree. A 5000 BC Norwegian person will similarly appear far more times in a typical Norwegian person's family tree than he will appear in a Japanese person's family tree. https://en.wikipedia.org/wiki/Identical_ancestors_point https://en.wikipedia.org/wiki/Identical_ancestors_point

titzer 6y ago
An intuition about the "appearing trillions of times in a family tree" is to realize that family trees are actually a binary tree extending backwards in time--i.e. each person has exactly two parents, who have exactly two parents, and so on. So N generations back, there are 2^N individuals. Obviously, there weren't 2^100 people on Earth at any point in time, so this backwards tree starts folding back on itself, containing duplications. Go back far enough and there is a set of individuals who were alive at a particular point in time that completely cover that forward tree. It helps to visualize this more as a mesh than a tree, or as a flowing river. The river divides around rocks and obstructions (those are points of temporary divergent evolution) but ultimately all flows together (convergent ancestry). We are truly one body of genetic material, and yet each is a unique combination of backwards traces. It's really very cool IMHO.
- TeMPOraL 6y ago
  To play with the river analogy: and then imagine that it flows next to a dye factory, and every now and then a droplet of dye finds its way to the stream, creating a colorful streak. That's to account for random mutations. And then what would an analogy look for prokaryotes - bacteria, archaea? If my understanding of biology is correct, it would be like an infinitely tall, densely tiered waterfall. There's some forward generational movement, but there's also plenty of lateral ones - exchanging gene packets "at runtime".
  - titzer 6y ago
    To be clear, the river can divide, too. That's speciation, where populations no longer interbreed because their offspring are either unviable or themselves cannot produce offspring.
  - rendall 6y ago
    To continue playing with our river analogy: consider a man fishing beside the river, who catches a large salmon. The man is ecstatic, for he is poor, and his family is hungry. Just as he draws his knife to gut it, the fish speaks! It says "Please do not kill me. Throw me back into the river, for I am the Fish King, and I will grant you 3 wishes. You can have whatever your heart desires." Astonished, the man agrees, and throws the talking fish back into the water. He speaks his 3 wishes into the air: to be rich, to be respected, and to be young again. Time passes. The man goes home to his hungry wife and child, hands empty. A day passes. A week. Then a year, and youth, wealth and respect remain elusive. A year after that, the man is fishing by the same riverbank - and remember, this is an analogous riverbank - an analogy for our ancestry - and the man catches the same fish! Or is it? It looks the same, but it does not speak. There is no recognition in its fishy eyes. It just lays on the shore, gasping, flopping. The man decides it's just a normal fish after all.
    - throwanem 6y ago
      The metaphor appears to have run away with you somewhat.
JPLeRouzic 6y ago
The point in the article is that at many generations ago, we are heavily inbred, it is not that we are all related. If you look at one generation ago one have 2 * 2 ^ 0 ancestors, at two generations, one have 2 * 2 ^ 1 ancestors, etc. At 27 generations one apparently has more ancestors than people in the world at that time. This apparent paradox stems from the fact that we are heavily inbred. Thus the article is correct.
- jerzyt 6y ago
  > The point in the article is that at many generations ago, we are heavily inbred, it is not that we are all related. I'm not following your point - maybe it's just a linguistic thing. To me, inbreeding implies relation, at least blood-relation, even when there was no other relation, e.g. conquering armies raping and pillaging. No argument with your math.
  - andi999 6y ago
    There might have been multiple separated inbreeding groups. Yes these groups are related among themselves but not inter-group.
    - zuminator 6y ago
      The article is saying that every person bears some relation to each other, even among distant groups. No further back than 3500 years ago existed a person who was a common ancestor to every currently living human being.
      - xbmcuser 6y ago
        3500 or 35000?
        pegasus 6y ago
        3500 sounds about right, if we consider only Eurasia. Otherwise, it could be farther back, but possibly not that much further, according to the wikipedia entry for Mitochondiral Eve (look for "most recent common ancestor"): "Monte Carlo simulations suggest the MRCA was born surprisingly recently, perhaps even within the last 5,000 years, even for people born on different continents."
jlawson 6y ago
Another important point here is that genes don't divide infinitely, so that if you go back some distance, you start finding ancestors from whom you actually didn't get any DNA. The book Who We Are and How We Got Here talks about this. When DNA recombines at conception, it only snips and stitches in a fairly limited number of places. It doesn't 'mix' finely like paint. It's more like taking two short pamphlets of ~25 pages, cutting each numbered page horizontally at a random vertical point, and then assembling a new pamphlet of the original size from each pair of pages (pamphlet A's page from above the cut, pamphlet B's from below). All this to say that if you go back something like 800 years, you have ancestors from whom you didn't get any genes at all. This means that these infintesimal mixings have even less impact than you'd think. A modern Japanese person could have a European ancestor who traveled to Asia a thousand years ago, but have zero genes from that ancestor. Which means that while that European is technically an 'ancestor', this is just a bit of historical trivia, it means literally nothing about that Japanese person's biology. --- On to the color commentary: I suspect that articles like this are heavily influenced by the politically-based drive to try to minimize intergroup genetic differences in humans. The reality is opposite the title - humans are far more distinct, especially on group levels, than is commonly understood. The notion that single common ancestors (among trillions) mean people from hugely divergent groups are 'related' in some meaningful way is just exploiting and expanding the ignorance of the public around how genetics actually work. It's arguably a pro-social thing to do; I'd say I agree with the philosophy here, but that doesn't make it true and the 'noble lie' seems anything but to me. The genetic evolutionary difference between distinct groups like Europeans, sub-Saharan Africans, and Australian Aborigines is something like 70,000 years of divergent evolution with very very minimal gene flow between the groups, in completely different environments. The genetic split between timber wolves and Chihuahuas was like 5,000 years ago and I bet they have common ancestors much more recently than that.
- JPLeRouzic 6y ago
  >> The genetic evolutionary difference between distinct groups like Europeans, sub-Saharan Africans, ... is something like 70,000 years of divergent evolution with very very minimal gene flow between the groups. Any citation?
irrational 6y ago
Aren’t you just reiterating the entire second half of the article?

by themgt 6y ago

titzer 6y ago

An intuition about the "appearing trillions of times in a family tree" is to realize that family trees are actually a binary tree extending backwards in time--i.e. each person has exactly two parents, who have exactly two parents, and so on. So N generations back, there are 2^N individuals. Obviously, there weren't 2^100 people on Earth at any point in time, so this backwards tree starts folding back on itself, containing duplications. Go back far enough and there is a set of individuals who were alive at a particular point in time that completely cover that forward tree. It helps to visualize this more as a mesh than a tree, or as a flowing river. The river divides around rocks and obstructions (those are points of temporary divergent evolution) but ultimately all flows together (convergent ancestry). We are truly one body of genetic material, and yet each is a unique combination of backwards traces. It's really very cool IMHO.

TeMPOraL 6y ago
To play with the river analogy: and then imagine that it flows next to a dye factory, and every now and then a droplet of dye finds its way to the stream, creating a colorful streak. That's to account for random mutations. And then what would an analogy look for prokaryotes - bacteria, archaea? If my understanding of biology is correct, it would be like an infinitely tall, densely tiered waterfall. There's some forward generational movement, but there's also plenty of lateral ones - exchanging gene packets "at runtime".
- titzer 6y ago
  To be clear, the river can divide, too. That's speciation, where populations no longer interbreed because their offspring are either unviable or themselves cannot produce offspring.
- rendall 6y ago
  To continue playing with our river analogy: consider a man fishing beside the river, who catches a large salmon. The man is ecstatic, for he is poor, and his family is hungry. Just as he draws his knife to gut it, the fish speaks! It says "Please do not kill me. Throw me back into the river, for I am the Fish King, and I will grant you 3 wishes. You can have whatever your heart desires." Astonished, the man agrees, and throws the talking fish back into the water. He speaks his 3 wishes into the air: to be rich, to be respected, and to be young again. Time passes. The man goes home to his hungry wife and child, hands empty. A day passes. A week. Then a year, and youth, wealth and respect remain elusive. A year after that, the man is fishing by the same riverbank - and remember, this is an analogous riverbank - an analogy for our ancestry - and the man catches the same fish! Or is it? It looks the same, but it does not speak. There is no recognition in its fishy eyes. It just lays on the shore, gasping, flopping. The man decides it's just a normal fish after all.
  - throwanem 6y ago
    The metaphor appears to have run away with you somewhat.

JPLeRouzic 6y ago

The point in the article is that at many generations ago, we are heavily inbred, it is not that we are all related. If you look at one generation ago one have 2 * 2 ^ 0 ancestors, at two generations, one have 2 * 2 ^ 1 ancestors, etc. At 27 generations one apparently has more ancestors than people in the world at that time. This apparent paradox stems from the fact that we are heavily inbred. Thus the article is correct.

jerzyt 6y ago
> The point in the article is that at many generations ago, we are heavily inbred, it is not that we are all related. I'm not following your point - maybe it's just a linguistic thing. To me, inbreeding implies relation, at least blood-relation, even when there was no other relation, e.g. conquering armies raping and pillaging. No argument with your math.
- andi999 6y ago
  There might have been multiple separated inbreeding groups. Yes these groups are related among themselves but not inter-group.
  - zuminator 6y ago
    The article is saying that every person bears some relation to each other, even among distant groups. No further back than 3500 years ago existed a person who was a common ancestor to every currently living human being.
    - xbmcuser 6y ago
      3500 or 35000?
      - pegasus 6y ago
        3500 sounds about right, if we consider only Eurasia. Otherwise, it could be farther back, but possibly not that much further, according to the wikipedia entry for Mitochondiral Eve (look for "most recent common ancestor"): "Monte Carlo simulations suggest the MRCA was born surprisingly recently, perhaps even within the last 5,000 years, even for people born on different continents."

jlawson 6y ago

Another important point here is that genes don't divide infinitely, so that if you go back some distance, you start finding ancestors from whom you actually didn't get any DNA. The book Who We Are and How We Got Here talks about this. When DNA recombines at conception, it only snips and stitches in a fairly limited number of places. It doesn't 'mix' finely like paint. It's more like taking two short pamphlets of ~25 pages, cutting each numbered page horizontally at a random vertical point, and then assembling a new pamphlet of the original size from each pair of pages (pamphlet A's page from above the cut, pamphlet B's from below). All this to say that if you go back something like 800 years, you have ancestors from whom you didn't get any genes at all. This means that these infintesimal mixings have even less impact than you'd think. A modern Japanese person could have a European ancestor who traveled to Asia a thousand years ago, but have zero genes from that ancestor. Which means that while that European is technically an 'ancestor', this is just a bit of historical trivia, it means literally nothing about that Japanese person's biology. --- On to the color commentary: I suspect that articles like this are heavily influenced by the politically-based drive to try to minimize intergroup genetic differences in humans. The reality is opposite the title - humans are far more distinct, especially on group levels, than is commonly understood. The notion that single common ancestors (among trillions) mean people from hugely divergent groups are 'related' in some meaningful way is just exploiting and expanding the ignorance of the public around how genetics actually work. It's arguably a pro-social thing to do; I'd say I agree with the philosophy here, but that doesn't make it true and the 'noble lie' seems anything but to me. The genetic evolutionary difference between distinct groups like Europeans, sub-Saharan Africans, and Australian Aborigines is something like 70,000 years of divergent evolution with very very minimal gene flow between the groups, in completely different environments. The genetic split between timber wolves and Chihuahuas was like 5,000 years ago and I bet they have common ancestors much more recently than that.

JPLeRouzic 6y ago
>> The genetic evolutionary difference between distinct groups like Europeans, sub-Saharan Africans, ... is something like 70,000 years of divergent evolution with very very minimal gene flow between the groups. Any citation?

irrational 6y ago

Aren’t you just reiterating the entire second half of the article?