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Thread: Y-Haplogroups and the «Common Ancestor»

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    Question Y-Haplogroups and the «Common Ancestor»

    Question 0: When is a haplogroup given an entirely new name (id est new letter)?


    Question 1:

    (Paraphrase) "About 60k years ago a new exodus from Africa took place, humans crossed the Arabian peninsula and reached the south of modern day Iran. Here a new mutation of the Y-haplogroup occured; this man is thought to be the common ancestor of all Eurasian and American populations"

    So, how can he be the only ancestor? I assume he didnt travel alone, thus other men just failed to procreate, or their line of descent came to an end sometime later for some reason, or ....?

    A continuation of the same question: Why are there no haplogroups like P* in Europe if R is a mutation of P (or for any β descendant of α in place Π) ?

    Imagine a tribe of people with only P. One day a man is born with a mutation so he has a new haplogroup called R. A couple of generations later the tribe has some amount of men with R-group.
    Then rumors of welfare checks in the promised land reach the tribe and a part of them decides to move there. Surely both P and R would be present among the emigrants. ("Everyone with Y-haplogroup R, two steps forward!" seems unlikely).

    Obviously there is something very basic that i havent yet grasped.
    Would someone be so kind to enlighten the peasant in me?

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    Quote Originally Posted by ReinaertDeVos View Post
    (Paraphrase) "About 60k years ago a new exodus from Africa took place, humans crossed the Arabian peninsula and reached the south of modern day Iran. Here a new mutation of the Y-haplogroup occured; this man is thought to be the common ancestor of all Eurasian and American populations"

    So, how can he be the only ancestor? I assume he didnt travel alone, thus other men just failed to procreate, or their line of descent came to an end sometime later for some reason, or ....?
    It means he was the nearest direct male ancestor. This is the person who if you went back from son to father to his father to his father etc..... who would be the common paternal ancestor of all Eurasians & Amerindians. We would have a line of descent from all of his contemporaries who left descendents but those lines would go back through a female line. In other words there was a failure of male heirs on the part of the other males who were with the common-paternal-ancestor of today's (racially) Europids, Mongolids & Amerindids. You are asking about the Y chromosome, that only traces the paternal line of descent. You have 1024 8xgreat-grandparents but only one of them is your direct paternal 8xgreat-grandfather from whom you inherited your Y chromosome. You descend from the other 1023 maternally. Go back 60,000 years or 2,500 to 3,000 generations (I won't even attempt to calculate the number of ancestral lines at that point), you would still have only the one direct paternal ancestor from whom your Y chromosome was passed down via, the rest are conected to via a female ancestress at some point.

    A continuation of the same question: Why are there no haplogroups like P* in Europe if R is a mutation of P (or for any β descendant of α in place Π) ?

    Imagine a tribe of people with only P. One day a man is born with a mutation so he has a new haplogroup called R. A couple of generations later the tribe has some amount of men with R-group.
    Then rumors of welfare checks in the promised land reach the tribe and a part of them decides to move there. Surely both P and R would be present among the emigrants. ("Everyone with Y-haplogroup R, two steps forward!" seems unlikely).

    Obviously there is something very basic that i havent yet grasped.
    Would someone be so kind to enlighten the peasant in me?
    The earth's population was very low when R was born. Less then a million? Basically R & his descendents were better at procreating children or at begatting sons, then the descendents of his brothers, uncles & cousins who were P. Q was also the son of a P & there are more Qs the Ps as the result of a few of the descendents of the first Q crossing the Bering strait & colonizing the Americas without any competition from other groups.

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    Thanks, the fog is beginning to disperse.

    Quote Originally Posted by Æmeric View Post
    The earth's population was very low when R was born. Less then a million? Basically R & his descendents were better at procreating children or at begatting sons, then the descendents of his brothers, uncles & cousins who were P. Q was also the son of a P & there are more Qs the Ps as the result of a few of the descendents of the first Q crossing the Bering strait & colonizing the Americas without any competition from other groups.
    1) If R is more succesfull and «better» than P and Q, why did that group triumph only among the population that went westwards but not among those who went east (also containing all three types: P,Q and R)?

    2) As far as I remember, the Y-chromosome possesses the least number of genes and has a relatively small influence on the phenotype except for the sex determination. So, how can a tiny change in the DNA-sequence of the smallest chromosome have such an impact on phenotype that it is decisive for succes?

    3)Would the «better» type R get all the females, was this the rule in prehistoric social groups? And was the selection ueberhaupt sexual?

    Sorry to bother you, but it is still not entirely lucid to me.

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    Quote Originally Posted by ReinaertDeVos View Post

    1) If R is more succesfull and «better» than P and Q, why did that group triumph only among the population that went westwards but not among those who went east (also containing all three types: P,Q and R)?
    There could be a variety of reasons why R males were more successful then P males, some of it just dumb luck. It would seem that those tribal groups that were made up of males with the R chromosome were better positioned (and took advantage of) to repopulate Europe at the end of the last Ice Age. The R1b subclades are predominate among the European populations that migrated overseas to the New World after 1492, this was another example of historical opportunity allowing the spread of the R(1b) chromosome, in this case it displaced Q - many New World mestizos & Indians now have R1b (and sometimes J or E1b) as a result of that expansion.

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    The Founder Effect & Genetic Drift

    Quote Originally Posted by ReinaertDeVos View Post
    1) If R is more succesfull and «better» than P and Q, why did that group triumph only among the population that went westwards but not among those who went east (also containing all three types: P,Q and R)?

    2) As far as I remember, the Y-chromosome possesses the least number of genes and has a relatively small influence on the phenotype except for the sex determination. So, how can a tiny change in the DNA-sequence of the smallest chromosome have such an impact on phenotype that it is decisive for succes?

    3)Would the «better» type R get all the females, was this the rule in prehistoric social groups? And was the selection ueberhaupt sexual?
    If you haven't already, familiarize yourself with these two evolutionary processes and never underestimate the explanatory power of them.

    Genetic Drift

    Founder Effect

    Many events that, at first, seem counterintuitive can be easily explained by these two principles. Especially when dealing with a small population.
    yDNA: R1a1a1
    mtDNA: H4a1
    Ancestry Painting: 100% European
    23andme Global Similarity: Dead center of English Cluster

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    Thanks again for the replies , I shall study these concepts thoroughly.

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