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Thread: Age of R1a and R1b

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    Age of R1a and R1b

    Question: Did the mutations that define haplogroups R1a and R1b both happen at the same time? In other words, do R1a and R1b necessarily have the same age?
    I asked this question before in the R1a group, but no one seems to have a good answer. I ask because every age estimate I have seen gives the same age for R1a and R1b (e.g. 22,800 YA). But isn't it possible that one of them split off first, say R1b, while the mutation from R1 to R1a happened perhaps much later?
    I guess the question applies equally to other haplogroup splits.
    Best regards,
    Jon

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    1 out of 1 members found this post helpful.
    Quote Originally Posted by hman View Post
    Question: Did the mutations that define haplogroups R1a and R1b both happen at the same time? In other words, do R1a and R1b necessarily have the same age?
    I asked this question before in the R1a group, but no one seems to have a good answer. I ask because every age estimate I have seen gives the same age for R1a and R1b (e.g. 22,800 YA). But isn't it possible that one of them split off first, say R1b, while the mutation from R1 to R1a happened perhaps much later?
    I guess the question applies equally to other haplogroup splits.
    Best regards,
    Jon
    I think they split at the same time when that one mutation occurred that the other line doesn’t have. Then over many thousands of years other defining mutations occurred separating them even more. The TMRCA or time of most recent common ancestor is probably different for R1b than for R1a because many lines die off over time at different rates. I1 split from
    I2 at the same time but has more defining mutations and a much more recent TMRCA.

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    Quote Originally Posted by mwauthy View Post
    I think they split at the same time when that one mutation occurred that the other line doesn’t have. Then over many thousands of years other defining mutations occurred separating them even more. The TMRCA or time of most recent common ancestor is probably different for R1b than for R1a because many lines die off over time at different rates. I1 split from
    I2 at the same time but has more defining mutations and a much more recent TMRCA.
    The thing is, I1 didn't, as you say, split from I2. They both split from I*, and this happened through two different mutations (or sets of mutations). The same with R1a and R1b, they both split from R1* through two different mutations. That is why I ask, could these mutations have happened at different times, perhaps hundreds or thousands of years between? Or is there some reason why they must have happened at (more or less) the same time?

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    1 out of 1 members found this post helpful.
    Since the mutation rate is relatively stable they would have arisen at roughly the same time. I think the latest consensus is a mutation rate of 150 years per SNP, so a disparity of a few hundred years would be difficult to rule out. The difference between R1a & R1b is that the latter gave rise to extant branches a bit earlier.

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    Quote Originally Posted by markod View Post
    Since the mutation rate is relatively stable they would have arisen at roughly the same time. I think the latest consensus is a mutation rate of 150 years per SNP, so a disparity of a few hundred years would be difficult to rule out. The difference between R1a & R1b is that the latter gave rise to extant branches a bit earlier.
    But is it really that simple? Supposedly it took about 4000 years from R1 appeared until it split into R1a and R1b. And a similar amout of time from R* appeared until it split into R1 and R2.

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    Quote Originally Posted by hman View Post
    But is it really that simple? Supposedly it took about 4000 years from R1 appeared until it split into R1a and R1b. And a similar amout of time from R* appeared until it split into R1 and R2.
    The way I look at it is that each snp refers to a particular man in time that has descendants today and that each haplogroup refers to a specific paternal lineage. So at a certain point there was no R1b or R1a and all R1 men had the same mutations and paternal ancestors in that branch of humanity. Such as me and my brother would have the same paternal past. However, if I’m born with a mutation that my brother doesn’t have then our haplogroup would split into 1 and 2 or A and B. Our descendants would also have mutations associated with either me or him.

    If all men throughout time had descendants and paternal lines never died off then there would be millions of subclades. However, most paternal lines die off and because of that subclades carry varying amounts of defining mutations and varying TMRCAs.

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    Quote Originally Posted by hman View Post
    But is it really that simple? Supposedly it took about 4000 years from R1 appeared until it split into R1a and R1b. And a similar amout of time from R* appeared until it split into R1 and R2.

    Yes. This only means that R1 dragged on for a while without leaving many descendants before the last common SNP between R1a/R1b arose.

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    Quote Originally Posted by hman View Post
    The thing is, I1 didn't, as you say, split from I2. They both split from I*, and this happened through two different mutations (or sets of mutations). The same with R1a and R1b, they both split from R1* through two different mutations. That is why I ask, could these mutations have happened at different times, perhaps hundreds or thousands of years between? Or is there some reason why they must have happened at (more or less) the same time?
    This kind of estimate isn't trying to say anything about when the first mutations in the R1a and R1b lineages actually happened. There is no reason they should have happened at the same time - they wouldn't be thousands of years apart though, Y DNA mutates too fast for that. The estimate is simply how long R1a and R1b have been diverging based on the number of different mutations they've accumulated between them.

    There's no way to tell when the first mutation in each lineage happened and it doesn't matter, that's not what is meant by "the age of" a haplogroup. The age you are talking about (what YFull calls the "formed" date) is the TMRCA of R1 and by definition will be the same for both R1a and R1b. (If you think about it genealogically the first men in the R1a and R1b lineages needn't have had any defining mutations at all.)

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    Quote Originally Posted by Megalophias View Post
    This kind of estimate isn't trying to say anything about when the first mutations in the R1a and R1b lineages actually happened. There is no reason they should have happened at the same time - they wouldn't be thousands of years apart though, Y DNA mutates too fast for that. The estimate is simply how long R1a and R1b have been diverging based on the number of different mutations they've accumulated between them.

    There's no way to tell when the first mutation in each lineage happened and it doesn't matter, that's not what is meant by "the age of" a haplogroup. The age you are talking about (what YFull calls the "formed" date) is the TMRCA of R1 and by definition will be the same for both R1a and R1b. (If you think about it genealogically the first men in the R1a and R1b lineages needn't have had any defining mutations at all.)
    Thanks for the clear answer in the first paragraph which seems to confirm what I stated in my question: the age of R1a and Rb1 are different, though unknown.

    But I disagree with the second paragraph. As I understand it the TMRCA of R1 is the same as the age of the *oldest* of R1a and R1b, the time when the first of these split from R1. Agreed? If so, is there a way to find out which one split first?

    Best regards,
    Jon

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    Quote Originally Posted by Megalophias View Post
    This kind of estimate isn't trying to say anything about when the first mutations in the R1a and R1b lineages actually happened. There is no reason they should have happened at the same time - they wouldn't be thousands of years apart though, Y DNA mutates too fast for that. The estimate is simply how long R1a and R1b have been diverging based on the number of different mutations they've accumulated between them.
    There's no way to tell when the first mutation in each lineage happened and it doesn't matter, that's not what is meant by "the age of" a haplogroup. The age you are talking about (what YFull calls the "formed" date) is the TMRCA of R1 and by definition will be the same for both R1a and R1b. (If you think about it genealogically the first men in the R1a and R1b lineages needn't have had any defining mutations at all.)
    Thanks for the clear answer in the first paragraph, which seems to confirm what I stated in my question: The age of R1a is different from R1b, though unknown.
    But I disagree with the second paragraph. As I understand it the TMRCA of R1 is the date that the first split from R1 happened, i.e when either R1a og R1b appeared for the first time. So the age of the two are not "by definition the same", rather by convention because we don't know the exact age of the one that origined later. The reason why I'm stressing this is because it could have a bearing on where each of them (R1a and R1b) origined.

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    Quote Originally Posted by Megalophias View Post
    This kind of estimate isn't trying to say anything about when the first mutations in the R1a and R1b lineages actually happened. There is no reason they should have happened at the same time - they wouldn't be thousands of years apart though, Y DNA mutates too fast for that. The estimate is simply how long R1a and R1b have been diverging based on the number of different mutations they've accumulated between them.

    There's no way to tell when the first mutation in each lineage happened and it doesn't matter, that's not what is meant by "the age of" a haplogroup. The age you are talking about (what YFull calls the "formed" date) is the TMRCA of R1 and by definition will be the same for both R1a and R1b. (If you think about it genealogically the first men in the R1a and R1b lineages needn't have had any defining mutations at all.)

    TMRA - The most recent ancestor.

    OP(hman) just f*ed up(pardon my french) whole question by mentioning 22800, which is TMRA for R1, which is correct TMRA when applying to both R1a AND R1b.

    However TMRA for R1a and for R1b will be different numbers:
    TMRA for R1a - 18300
    TMRA for R1b - 20400


    Yes, R1b is older mutation - it happened first(it should be named R1a). And since some haplogroups have underwent recent naming changes and now are named chronologically correct in alphabetical order, R1b and R1a should be renamed accordingly to avoid confusions in future.

    PS For those who are wondering, TMRA for R currently is estimated 28200. TMRA most probably has nothing to do with real dates, though.

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    Quote Originally Posted by hman View Post
    Thanks for the clear answer in the first paragraph, which seems to confirm what I stated in my question: The age of R1a is different from R1b, though unknown.
    But I disagree with the second paragraph. As I understand it the TMRCA of R1 is the date that the first split from R1 happened, i.e when either R1a og R1b appeared for the first time.
    No, TMRCA means Time to Most Recent Common Ancestor. Whoever was the latest ancestor (in the paternal line) to both R1a and R1b men was the Most Recent Common Ancestor of R1, it is necessarily one man who lived at a certain time. This is the age that is the same for both. The first actual mutation of the R1a or R1b line didn't have to occur at that time, if that's what you mean by "appeared". The splitting from R1 is just different sons being born to the same father, one line would be descended from an older brother and one from a younger brother, but of course there's no way to know which and it makes no difference. The individual TMRCAs of R1a and R1b are different of course.

    Could you explain in terms of actual fathers, sons, and mutations in the past what you are trying to get at? I really don't follow.

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