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Post by NuSapiens on Mar 14, 2005 20:42:31 GMT -5
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Post by Curious6 on Mar 15, 2005 10:17:16 GMT -5
Hi! I would just to like comment on the meaning of the term 'purity'. This is of course applied here as applied to races.
As you might very well know, genetic diversity is largest between individuals of the same group than genetic diversity between people of different groups. The numbers often given are 85% genetic variation between races, and 15% genetic variation between races. What does this imply? Basically, it means that the genetic diversity accumulated largely before the migration out of Africa, and that due to gene flow between continents after partial isolation (where 'new' mutations leading to 'new' genetic diversity would have occurred) would have maintained the percentage of genetic diversity shared between races.
So my question is, how do you define 'purity'? Do you have any genetic basis for doing this? Just a comment! Thanks!
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Post by Curious6 on Mar 15, 2005 10:42:13 GMT -5
By the way, how do you calculate admixture rates in your samples?
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Post by NuSapiens on Mar 15, 2005 19:00:19 GMT -5
The worth of these maps really depends upon the mathematical and sampling methods used to generate them. As has been pointed out, this data was published by a commercial firm (not an academic research team), and did not detail these methods, unfortunately. I use it because it's the best data I have of the type. These types of tests assess huge amounts of data (genetic markers in individuals) to divide individuals into geographical groups. Purity is defined as individual similarity to statistically derived population norms. The data is from www.ancestrybydna.com. I compiled it in Excel and then made the map as described on my blog entry. Check out Ancestry By DNA's website for more on their methods - and if you find their published material insufficient, encourage them to share more about their sampling and statistical methods. Hopefully, an academic study similar to Rosenberg's will be published, so that I needn't rely upon a commercial source for data to crunch. And to address Lewontin's notion that most diversity is found within races and not between them: these studies and commercial test rely upon markers that do vary between populations. |
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Post by Curious6 on Mar 16, 2005 2:42:01 GMT -5
OK, thanks for answering. So as I see it, you are compiling these charts using markers that do vary between races, that's interesting. Are the markers used by them then within the 15% of genetic diversity between races (i.e. restricted to them)? I thought you used some statistical method to calculate relative frequency of alleles or something else in order to derive these maps. The maps make more sense now.
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Post by Curious6 on Mar 21, 2005 12:59:58 GMT -5
Hey NuSapiens, there is a question I have about the amount of genetic variation in the human species that really intrigues me. I am a bit confused by what is meant when scientists state that 85% of total genetic variation is found among individuals within a group, rather than genetic variation between groups or continents. Before I used to think it referred to that only 85% of the total genetic variants to be found in humans could be found in a specific group, and that the remaining 15% would be either group- or continent-specific. I have come across various websites on the Internet who have this same interpretation as I do of the genetic variation. However, in an interview I read with Lewontin on the PBS special on Race www.pbs.org/race he states something different about genetic variation. He mentions that the large majority (85%) of alleles have the same proportion among different groups, and that the remaining alleles are also to be found in different groups, but in different proportions. What is the correct view? I am not sure on how to interpret this, and I'm sure you can maybe clarify this a bit. Thanks! |
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Post by Kabbealompost on Mar 27, 2005 12:50:17 GMT -5
WTF is "racial purity"?
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