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This would actually be really surprising, wouldn’t it? I would think the default would be a pool of pre-human hominids which gradually changed over time and eve

This would actually be really surprising, wouldn’t it? I would think the default would be a pool of pre-human hominids which gradually changed over time and eventually crossed the arbitrary line we deem “human”. I suppose in theory one individual may have had the last teeny mutation to cross over that arbitrary line which then spread everywhere to cross the rest of the pool over, but it seems more likely that bits of the “human” features developed in different populations over time and eventually and gradually merged through cross breeding (after each mutation was already in multiple individuals). The linear view with a singleton seems overly simplistic for “humans” overall. For a single trait it still seems overly simplistic and unlikely, but not nearly as radically so. EDIT I think there is some confusion here. I believe the article claim is that the feature "blue eyes" may have originated from a mutation in a single individual organism, or at least bottlenecked in a single individual organism. OP sounds like they are saying "yeah, now do humans", but the entire feature complex "human" is almost certainly not like that. If all OP is saying is that there is probably at least one tiny feature in humans which originated from a mutation in a single individual organism, then sure this is trivially true, but that situation is very, very different from the article situation.

im3w1l 4y ago
Well you have two parents, four grandparents, eight great-grandparents etc. Eventually inbreeding (if you can call it that when it's really distant relatives) starts becoming a factor so that some person may take up multiple "slots" in your family tree. But either way, it would seem that if you go far enough back every single human will be an ancestor of yours. Edit: Just to clarify what I'm trying to get at is that there are probably quite a lot of Ancestors That Everyone Descend from.
- denton-scratch 4y ago
  Agreed (FSVO "quite a lot"). But the same argument applies to blue eyes.
- SideburnsOfDoom 4y ago
  > But either way, it would seem that if you go far enough back every single human will be an ancestor of yours. The nearest "ancestor of all living people" is calculated to 150 000 to 300 000 years ago, depending on which one you're talking about https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Mitochondrial_Eve or https://en.wikipedia.org/wiki/Y-chromosomal_Adam https://en.wikipedia.org/wiki/Y-chromosomal_Adam
  - irrational 4y ago
    Or, 2,000 years ago - if by “all living people” you mean everyone alive right now. https://www.scientificamerican.com/article/humans-are-all-more-closely-related-than-we-commonly-think/ https://www.scientificamerican.com/article/humans-are-all-mo...
    - denton-scratch 4y ago
      Oh, that's interesting. My father researched a family tree; not rigorously, like Mormons do, but he spent about a decade tramping around the country, visiting graveyards and inspecting parish records. I have a bound volume of the tree. He claimed descent from (a) William The Conqueror, (b) Lady Godiva, and (c) Charlemagne. I don't have his records, only the tree. The links are pretty ropey, especially when you reach further back. And he imported big chunks of it from trees built by others. His conclusions seem pretty implausible, but that article makes them seem a bit more plausible.
  - im3w1l 4y ago
    Well given that blue eyes is neither neither mt-dna or y-chromosome, I made an argument about the autosomal "normal dna" that is inherited from both sides.
SideburnsOfDoom 4y ago
> everyone may descend from a single ancestor! ... This would actually be really surprising, wouldn’t it? No, it would be statistically inevitable: https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Y-chromosomal_Adam https://en.wikipedia.org/wiki/Y-chromosomal_Adam "around 200,000 to 300,000 years ago" although we're not descended from _only_ this one ancestor on each side, we are all descended from that one.
- irrational 4y ago
  For everyone alive today, it is probably even much closer in time (perhaps as recently as 2,000 years ago). https://www.scientificamerican.com/article/humans-are-all-more-closely-related-than-we-commonly-think/ https://www.scientificamerican.com/article/humans-are-all-mo...
  - SideburnsOfDoom 4y ago
    Right. Those are via different methods. "Mitochndrial eve" is via female line only - i.e. mother's mother's mother's mother etc. Similarly the Y-chromosome Adam is via male line only. If we use both sides (e.g. mother's father's mother's father), then it's much closer.
- pfannkuchen 4y ago
  I believe the article is claiming that the feature "blue eyes" has a single organism bottleneck (or origin) in the past. If this were also true for the feature complex "human", that would be very surprising. If all that is being claimed here is that humans all have at least one common ancestor among many non-common ancestors, then sure that is trivially very likely. It is also nothing like what is being claimed about blue eyes IIUC...
tzs 4y ago
Consider some arbitrary point far in the past and pick a random human, and consider their descendants. Human population was growing almost exponentially [1] and continued to do so for many thousands of years. If you keep track of the number of descendants of that random human who are alive over time, what you'll find is that in almost all cases it either goes to 0 over a short number of generations or it increases almost exponentially until it hits some limit such as a physical barrier that stops growth in all the places their descendants live and prevents their descendants from leaving. If a few of their descendants can travel, then in their new area their descendants either go to 0 or exponentially spread in the new area. It doesn't take a super long time, in the case where the number of descendants doesn't go to 0 for the number of descendants to grow to the point where everyone is a descendant of that random human. But note that the same is true for any other random human we might have picked at that time. Every person who was alive at that time either has no living descendants or everyone now alive is a descendant of theirs. The same is true for any point farther back than the arbitrary point we picked, because anyone alive at that earlier point who has any descendant who reached the first point will be an ancestor of everyone now alive, because their descendant who reached the first point is. The most recent point at which everyone then alive is either an ancestor of all now alive or of none now alive is called the "all common ancestors point" or the "genetic isopoint". Most researchers think the genetic isopoint was somewhere in the range of 4000-15000 years ago. There's also a point of interest that occurs between the genetic isopoint and the present called the "most recent common ancestor point". That is the point where any two people now alive have a common ancestor at that point, but there are groups of three people where there is no common ancestor of all three at that point. There's also the "matrilineal most recent common ancestor" and "patrilineal most recent common ancestor", which are like the "most recent common ancestor" except you only counts female descendants or male descendants, respectively. These are also called the "Mitochondrial Eve" and "Y-chromosomal Adam", respectively. These are even farther back than the "all common ancestor point" You can also look at this going backwards. As you go back the number of logical ancestors you have doubles each generation. But that exponentially growing number of logical ancestors has to map to the almost exponentially shrinking number of people, and so some distinct logical ancestors of yours are implemented by the same physical ancestor. The farther back you go the more people's ancestor trees each physical person then alive is in, unless they are in none. And so you again find the most recent common ancestor point, and the all common ancestor point, and the matrilineal and patrilineal most recent common ancestor points. If the genetic isopoint really was less than 15000 years ago, you can make some interesting inferences. For instance the Neanderthals went extinct around 40000 years ago. That's farther back than the genetic isopoint. Since some people now alive are known to have Neanderthal ancestors (because they have some Neanderthal DNA) then everyone now alive must have Neanderthal ancestors. Note that this doesn't mean everyone alive must have Neanderthal DNA. You only pass half your genes on to your kids so you can eventually end up with descendants who don't actually have any of your genes. Same with the Denisovans. They went extinct before the genetic isopoint, and some modern humans are known to have Denisovan ancestors and we we can conclude that we all do. [1] I say "almost" exponentially because instead of e^(at) where a is constant, a is variable and has long term been slowly decreasing.
denton-scratch 4y ago
> I think there is some confusion here. You're quite right; although I was being flippant, rather than confused.
- pfannkuchen 4y ago
  I wasn’t saying you were confused, I was saying that responses to my comment had not grokked what exactly I thought was surprising.

im3w1l 4y ago

Well you have two parents, four grandparents, eight great-grandparents etc. Eventually inbreeding (if you can call it that when it's really distant relatives) starts becoming a factor so that some person may take up multiple "slots" in your family tree. But either way, it would seem that if you go far enough back every single human will be an ancestor of yours. Edit: Just to clarify what I'm trying to get at is that there are probably quite a lot of Ancestors That Everyone Descend from.

denton-scratch 4y ago
Agreed (FSVO "quite a lot"). But the same argument applies to blue eyes.
SideburnsOfDoom 4y ago
> But either way, it would seem that if you go far enough back every single human will be an ancestor of yours. The nearest "ancestor of all living people" is calculated to 150 000 to 300 000 years ago, depending on which one you're talking about https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Mitochondrial_Eve or https://en.wikipedia.org/wiki/Y-chromosomal_Adam https://en.wikipedia.org/wiki/Y-chromosomal_Adam
- irrational 4y ago
  Or, 2,000 years ago - if by “all living people” you mean everyone alive right now. https://www.scientificamerican.com/article/humans-are-all-more-closely-related-than-we-commonly-think/ https://www.scientificamerican.com/article/humans-are-all-mo...
  - denton-scratch 4y ago
    Oh, that's interesting. My father researched a family tree; not rigorously, like Mormons do, but he spent about a decade tramping around the country, visiting graveyards and inspecting parish records. I have a bound volume of the tree. He claimed descent from (a) William The Conqueror, (b) Lady Godiva, and (c) Charlemagne. I don't have his records, only the tree. The links are pretty ropey, especially when you reach further back. And he imported big chunks of it from trees built by others. His conclusions seem pretty implausible, but that article makes them seem a bit more plausible.
- im3w1l 4y ago
  Well given that blue eyes is neither neither mt-dna or y-chromosome, I made an argument about the autosomal "normal dna" that is inherited from both sides.

SideburnsOfDoom 4y ago

> everyone may descend from a single ancestor! ... This would actually be really surprising, wouldn’t it? No, it would be statistically inevitable: https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Y-chromosomal_Adam https://en.wikipedia.org/wiki/Y-chromosomal_Adam "around 200,000 to 300,000 years ago" although we're not descended from _only_ this one ancestor on each side, we are all descended from that one.

irrational 4y ago
For everyone alive today, it is probably even much closer in time (perhaps as recently as 2,000 years ago). https://www.scientificamerican.com/article/humans-are-all-more-closely-related-than-we-commonly-think/ https://www.scientificamerican.com/article/humans-are-all-mo...
- SideburnsOfDoom 4y ago
  Right. Those are via different methods. "Mitochndrial eve" is via female line only - i.e. mother's mother's mother's mother etc. Similarly the Y-chromosome Adam is via male line only. If we use both sides (e.g. mother's father's mother's father), then it's much closer.
pfannkuchen 4y ago
I believe the article is claiming that the feature "blue eyes" has a single organism bottleneck (or origin) in the past. If this were also true for the feature complex "human", that would be very surprising. If all that is being claimed here is that humans all have at least one common ancestor among many non-common ancestors, then sure that is trivially very likely. It is also nothing like what is being claimed about blue eyes IIUC...

tzs 4y ago

Consider some arbitrary point far in the past and pick a random human, and consider their descendants. Human population was growing almost exponentially [1] and continued to do so for many thousands of years. If you keep track of the number of descendants of that random human who are alive over time, what you'll find is that in almost all cases it either goes to 0 over a short number of generations or it increases almost exponentially until it hits some limit such as a physical barrier that stops growth in all the places their descendants live and prevents their descendants from leaving. If a few of their descendants can travel, then in their new area their descendants either go to 0 or exponentially spread in the new area. It doesn't take a super long time, in the case where the number of descendants doesn't go to 0 for the number of descendants to grow to the point where everyone is a descendant of that random human. But note that the same is true for any other random human we might have picked at that time. Every person who was alive at that time either has no living descendants or everyone now alive is a descendant of theirs. The same is true for any point farther back than the arbitrary point we picked, because anyone alive at that earlier point who has any descendant who reached the first point will be an ancestor of everyone now alive, because their descendant who reached the first point is. The most recent point at which everyone then alive is either an ancestor of all now alive or of none now alive is called the "all common ancestors point" or the "genetic isopoint". Most researchers think the genetic isopoint was somewhere in the range of 4000-15000 years ago. There's also a point of interest that occurs between the genetic isopoint and the present called the "most recent common ancestor point". That is the point where any two people now alive have a common ancestor at that point, but there are groups of three people where there is no common ancestor of all three at that point. There's also the "matrilineal most recent common ancestor" and "patrilineal most recent common ancestor", which are like the "most recent common ancestor" except you only counts female descendants or male descendants, respectively. These are also called the "Mitochondrial Eve" and "Y-chromosomal Adam", respectively. These are even farther back than the "all common ancestor point" You can also look at this going backwards. As you go back the number of logical ancestors you have doubles each generation. But that exponentially growing number of logical ancestors has to map to the almost exponentially shrinking number of people, and so some distinct logical ancestors of yours are implemented by the same physical ancestor. The farther back you go the more people's ancestor trees each physical person then alive is in, unless they are in none. And so you again find the most recent common ancestor point, and the all common ancestor point, and the matrilineal and patrilineal most recent common ancestor points. If the genetic isopoint really was less than 15000 years ago, you can make some interesting inferences. For instance the Neanderthals went extinct around 40000 years ago. That's farther back than the genetic isopoint. Since some people now alive are known to have Neanderthal ancestors (because they have some Neanderthal DNA) then everyone now alive must have Neanderthal ancestors. Note that this doesn't mean everyone alive must have Neanderthal DNA. You only pass half your genes on to your kids so you can eventually end up with descendants who don't actually have any of your genes. Same with the Denisovans. They went extinct before the genetic isopoint, and some modern humans are known to have Denisovan ancestors and we we can conclude that we all do. [1] I say "almost" exponentially because instead of e^(at) where a is constant, a is variable and has long term been slowly decreasing.

denton-scratch 4y ago

> I think there is some confusion here. You're quite right; although I was being flippant, rather than confused.

pfannkuchen 4y ago
I wasn’t saying you were confused, I was saying that responses to my comment had not grokked what exactly I thought was surprising.