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    What's the difference between a lineal descendent, and a "normal" descendent?

    Lineal is blood, right? So, I'm a lineal descendent of my great grandfather, while I'm not a lineal descendent of..... my what?

    Second, if John is a great grandson of Walter, how is John the most recent "common ancestor"? :confused:

    This is probably blindingly obvious, but I seem to be going through a brain freeze.

    I'm reading about WD Hamilton's kin selection theory.
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    Lineal is slightly more direct than that. You're a lineal descendant of your father, grandfather, great-grandfather etc. However, you are not a lineal descendant of your uncle, despite being related. I would say a lineal descendant is a "normal" descendant.

    Your second question has no context really. Obviously John is not a most recent common ancestor if he's being compared to people older than him. You need at least 4 individuals to talk about most recent common ancestors:
    Say John and Colin are cousins, and they are both descendants of David (grandfather) and Walter (great grandfather). Their most recent common ancestor is therefore David, as they are the children of different individuals among his offspring, and he was more recent in both their lineages than Walter.

    Does that all make sense?
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    (Original post by jay8)
    Lineal is slightly more direct than that. You're a lineal descendant of your father, grandfather, great-grandfather etc. However, you are not a lineal descendant of your uncle, despite being related. I would say a lineal descendant is a "normal" descendant.

    Your second question has no context really. Obviously John is not a most recent common ancestor if he's being compared to people older than him. You need at least 4 individuals to talk about most recent common ancestors:
    Say John and Colin are cousins, and they are both descendants of David (grandfather) and Walter (great grandfather). Their most recent common ancestor is therefore David, as they are the children of different individuals among his offspring, and he was more recent in both their lineages than Walter.

    Does that all make sense?
    Thanks Jay - may I pester you with one or two follow up questions.

    I assume lineal descendents also include my mother, grandmother, etc.
    I don't see in what sense an uncle or aunt can be termed "descendents". One doesn't derive from them in any way. Lineal descendent, then, to me, just seems tautological. Clearly I'm not right though?

    Wouldn't the cousins also have David's wife (grandmother) as a common ancestor? Both should be tied for equal status as "most recent".
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    (Original post by PrimateJ)
    Thanks Jay - may I pester you with one or two follow up questions.

    I assume lineal descendents also include my mother, grandmother, etc.
    I don't see in what sense an uncle or aunt can be termed "descendents". One doesn't derive from them in any way. Lineal descendent, then, to me, just seems tautological. Clearly I'm not right though?

    Wouldn't the cousins also have David's wife (grandmother) as a common ancestor? Both should be tied for equal status as "most recent".
    Sorry, my explanation wasn't quite clear enough!

    You are absolutely right. As far as I understand it, "lineal descendant" = "descendant". It's just another word put in to make it sound more clever. I guess you might use it in particular when you know the family tree of the person you're looking at, and can trace it back directly. But essentially it's all the same thing.

    The cousins would indeed also have David's wife as the equal most recent common ancestor. I've never seen the term used in this kind of context before, it was just an easy way of explaining it. It's mainly used in evolutionary biology to look at phylogenies that aren't as complete as human ones. For example, "mitochondrial Eve" is the most recent common ancestor of all the human mitochondrial DNA in today's population. It's also used a lot in coalescent theory (looking at ancestry of particular genes). I.e. if you have 2 forms of a particular gene, you can look at how many differences there are between them, and use the mutation rate to work out how long it's been since the original gene they both came from existed in an individual. This gene would have been the most recent common ancestor of the 2 forms being studied.
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    (Original post by jay8)
    Sorry, my explanation wasn't quite clear enough!

    You are absolutely right. As far as I understand it, "lineal descendant" = "descendant". It's just another word put in to make it sound more clever. I guess you might use it in particular when you know the family tree of the person you're looking at, and can trace it back directly. But essentially it's all the same thing.

    The cousins would indeed also have David's wife as the equal most recent common ancestor. I've never seen the term used in this kind of context before, it was just an easy way of explaining it. It's mainly used in evolutionary biology to look at phylogenies that aren't as complete as human ones. For example, "mitochondrial Eve" is the most recent common ancestor of all the human mitochondrial DNA in today's population. It's also used a lot in coalescent theory (looking at ancestry of particular genes). I.e. if you have 2 forms of a particular gene, you can look at how many differences there are between them, and use the mutation rate to work out how long it's been since the original gene they both came from existed in an individual. This gene would have been the most recent common ancestor of the 2 forms being studied.
    Cheers. Have some of my (unfortunately measly) reps
 
 
 
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