Sciguy, Every now and then I get the distinct impression that you might possibly be a reasonable person, despite all evidence to the contrary. Given the possibility that this is the case, I am willing to continue the discussion in order to clarify the points being made. Lets see what happens.
To start with I think that you misread a statement.
The idea that Every genetic variation currently in play in the vast population of the world, has been passed down to the current generations from their ancestors. Every specific variation has been passed down through the ages, from ancestor to descendant, since its inception is not possible since it precludes the origin of novel genetic variation (a prerequisite for natural selection, speciation).
I think if you read it again with the specific understanding that 'since its inception' refers to the inception of the variation, then you will see that it not only allows for novel genetic variation but is actually describing 'novel genetic variation'.
The idea that every person that suffers from any specific disease or condition that is based upon a single genetic variation, is by definition related to every other person that shares that same variation is also false. It presumes that two unrelated individuals would not be able to have the same specific disease based on a single genetic variation, and of course, they can.
You are presuming then, that the same 'novel genetic variation' that causes a specific diseases, can crop up randomly throughout the population. Whereas the accepted cladistic classification philosophy (which Ancesry depends upon) assumes that individual genetic variations enter the population once and pass down the specific hereditary branch from that particular instance.
Both my analysis and the Ancestry technology assume that novel genetic variations enter the population once. Therefore, again by definition;
It presumes that two unrelated individuals would not be able to have the same specific disease based on a single genetic variation, and of course, they can.
is incorrect. You will need to demonstrate how two individuals can obtain the same genetic variation WITHOUT being descended from the same individual in which the 'novel genetic variation' first occurred.
You are drawing too fine a line with your concepts of genetic variation, relatedness and ancestry. You share more than 50% of your genes with a banana. You and a banana ARE related, but no one would view this relationship as the same as the one you're suggesting.
A throw away line perhaps, but one with a point in it. IF one found a genetic variation within the human genome that was in fact 'shared' by bananas, one could correctly assume that the variation 'occurred' in an organism so far back in the evolutionary history AND such organism was an ancestor to both human and banana. That is the point of the discussion and the basis of DNAG's Ancestral application.
You suggest, and rightly so, that the web of genetic variations as it manifests itself throughout the human population is much too complex to gain much leverage from this premise. Nevertheless it is the cornerstone of the technology. All else is built upon it.
All individuals that carry a unique genetic variation reside on the same ancestral branch, however, due to the vagaries of genetic transference, not all branch members carry the variance. Grandad may pass it to son and then grand-daughter, but Grandad's other children may not get it nor then will the other grandchildren. On the other hand the individual grandchild that carries the variance can trace it back directly to its source.
Conclusion; single genetic variations are part of the larger picture of ancestry, but do not by themselves demonstrate that groups of people that carry a specific genetic variation, share not only an ancestor, but are a part of the same bio-geographical group that contains that individual ancestor.
I think that upon reflection, you will find that they do. Absolutely. Furthermore, if they didn't then DNAG and its application of its Ancestry product to seek out such a connection, would be dead in the water.
Sciguy, much as we disagree, you are the only individual who has taken the time to try to have meaningful discussions about the science and the technology. Please understand that I appreciate the effort and look forward to your response.
regards,
frog
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