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Thread: 40.000 years of human presence in Southern Europe: the Italian case study

  1. #26
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    Pax Augusta: Well as I said, I only read the abstract. I took Principal Component Scores to mean they ran Principal Components to come up with the smallest number of Factors (components) to explain Populations. So I am not sure then what they mean by Principal components Scores. I took Principal Components analysis in a Multi-variate Statistics course (more economic based area). So when I see Principal Components, I think of running it and getting the eigen values of all the factors and ones that are > 1 are generally included as the variables (explanatory factors) to explain some Dependent variable, etc. Those less than 1 seem to add very little incremental explanatory power, although some might argue 1 is to strict a cut off.

    Ok, so I assumed they were using autosomal DNA samples. Again, I only have read the abstract. So if I may ask, can you briefly describe how these Principal Component scores and Synthetic maps works. They used gene frequencies? Ok, well that does seem questionable. Am I to understand they are using Principal Component Scores to be something different than what I described above?

  2. #27
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    Quote Originally Posted by Palermo Trapani View Post
    Pax Augusta: Well as I said, I only read the abstract. I took Principal Component Scores to mean they ran Principal Components to come up with the smallest number of Factors (components) to explain Populations. So I am not sure then what they mean by Principal components Scores. I took Principal Components analysis in a Multi-variate Statistics course (more economic based area). So when I see Principal Components, I think of running it and getting the eigen values of all the factors and ones that are > 1 are generally included as the variables (explanatory factors) to explain some Dependent variable, etc. Those less than 1 seem to add very little incremental explanatory power, although some might argue 1 is to strict a cut off.

    Ok, so I assumed they were using autosomal DNA samples. Again, I only have read the abstract. So if I may ask, can you briefly describe how these Principal Component scores and Synthetic maps works. They used gene frequencies? Ok, well that does seem questionable. Am I to understand they are using Principal Component Scores to be something different than what I described above?

    I have read the study. At that time, autosomal DNA analysis did not yet exist. Yes, they used some kind of alleles frequencies. However if you want to understand what I'm saying, and it's me who can't explain myself, read the first introductory chapter of David Reich's book ("Who We Are and How We Got Here") where he talks about Cavalli-Sforza (Piazza was one of the main collaborators of Cavalli-Sforza) and where Reich explains why many things hypothesized by Cavalli-Sforza turned out not to be true, despite acknowledging his role as a pioneer.

  3. #28
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    Pax: Ok, well I would think some of these Researchers would have had access to some DNA even back then, but yes it wasn't the SNP type testing we have today. FBI labs in the USA by the 1980's had DNA and were analyzing it for Crime cases, but I have to go back and see exactly in what context DNA was being used that way. That was a long time ago and I think it related to what was referred to then a Blood test, etc where they had a suspect and sampled his/her relatives and then got matches and arrested their guy.

    I have not read Reich's book and I agree I do need to get a copy of it.

    Thanks again.

  4. #29
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    Quote Originally Posted by Palermo Trapani View Post
    I have not read Reich's book and I agree I do need to get a copy of it.

    Thanks again.
    Many things are explained there.

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