More woeful misunderstandings of DNAPrint tests
The latest in a series of critiques of the DNAPrint tests is at John Hawkes’ blog. This, as usual, is based on certain, not unpredictable misunderstandings.
1. While Hawks does mention the issue of statistical significance, he doesn’t follow through on it to completion. If a low level of affiliation (eg, “Native American” in Greeks) is below the level of statistical significance and the “confidence intervals” overlap zero, then that result is statistically equivalent to zero. Given that tests using continuously distributed alleles will have a low error rate, and given that levels of statistical significance are given on the company’s website, these low level results should not be taken too seriously.
The company is undertaking putting together a more advanced version of the tests that may in part clear up what is going on with these very low affiliation results. However, it is quite clear that making a big deal, for example, out of a 4% Native American result in a Greek is a waste of time. It is not significant; the company admits that, so why make an issue of it? That some people misunderstand and/or misuse the test does not logically invalidate the worth of the test itself.
2. A serious misunderstanding – and one that DNAP itself may have some responsibility for because their explanations of the tests are rather poor – is the idea that DNAPrint’s categories somehow represent the specific populations they are named after in a direct fashion, and, in so doing, the categories represent direct descent from these “pure populations” – which Hawks sees as a serious flaw in the assumptions built into the tests.
The problem is that the categories obviously do not directly represent any modern populations since, for example, real-life South Asians and Middle Easterners are NOT 100% “South Asian” or “Middle Eastern” when tested with DNAP. Furthermore, DNAP admits, for example, that they really are not sure what their Euro 1.0 categories exactly represent; one cannot say that DNAPrint’s categories represent ancient “pure populations”, either. The straw man of “racial purity” is irrelevant here. There needs to be no “pure populations” as an assumption for any of these tests.
Important - What the categories represent are those sets of gene frequencies that characterize the predominant distinctive ancestral genetic component of particular population groups.
That is much different than saying the category represents the group itself. It may well be, for example, that, even in ancient times, the populations of the Middle East were never “racially pure.” Nevertheless, these populations share a particular predominant genetic component that distinguishes them from other major population groups, and this component can be determined and roughly quantified via the DNAPrint tests. Thus, the assumption built into the test is that different populations have these distinctive genetic components - not that the populations themselves, including the parental populations from which the gene frequencies were determined, are “pure” or not. In other words, the tests are pulling out from these populations that predominant component that distinguishes the population from others; that same ancestry may well be a minor component of the ancestry of another group.
3. Therefore, even if there is statistically significant “Native American” in a Greek, the test is not saying that the Greek in question is descended from Native Americans! Rather, that the Greek contains, for whatever reason, a minor genetic affiliation with gene frequencies that represent what is the predominant distinctive portion of Native American SNP variation. DNAPrint openly admits that they cannot distinguish how and why these gene frequencies are present:
Thus, the DNAPrint tests are really not genealogy tests per se, nor are they tests of absolute racial ancestry. One cannot take a set of DNAPrint results as a literal reading of one’s exact ancestry. One cannot say, hey, 35% of my ancestors were Northwest Europeans, 15% were South-Eastern Europeans, 10% were Middle Easterners, 10% were Native Americans, 10% were Africans and 20% were East Asians.
Instead the tests are relative and comparative, they allow you to compare how individuals and groups compare to other individuals and groups with respect to their relative genetic affiliations to the predominant distinctive gene frequency patterns of various major population groups. Different ethnic groups tend to have distinctive patterns of these affiliations. So that, one does not say that a South Asian is “100% South Asian”, but that South Asians tend to be characterized by a set of affiliations including a predominant “South Asian” component, usually with a strong “East Asian” minority affiliation, etc.
Whether these affiliations can be correlated to actual recent (or ancient) admixture depends on context. A person who tests as “60% Native American” is undoubtedly significantly derived from recent Native American ancestors. Some white person who is “12% Native American” – that depends. If they are a Greek from Athens, obviously they are not having direct ancestry from actual Native Americans. If they are white Americans whose ancestors came to the New World in the 18th century, and may have admixed with Native Americans, that is a stronger possibility.
Updated future tests may be able to “time” the “admixture” event based on the level of clustering of particular alleles, but for now, it is not possible.
The results must be viewed in the context of what is known of the person’s background; in this case, when used in a comparative sense, focusing on statistically significant results, then they are very informative.
4. I don’t quite understand Hawks’ problem with the South Asian data. South Asia is at the geographical/racial crossroads between the Caucasian and Mongoloid worlds. Furthermore, a variety of genetic studies (which I believe I’ve already mentioned on this blog) demonstrate the unique, mixed nature of South Asian populations and, in particular, East Asian influences (HLA studies, as well as the Ray et al Alu work). Looking at populations of northern and eastern India, Nepal, Bangladesh, Burma etc, I fail to see why it is so impossible that South Asians are a Caucasian/Mongoloid mix, with the former of course predominating, while certain SE Asian populations may contain a certain Caucasian influx from South Asians. I fail to see as well why the people of Hawaii would not test out as predominantly in the East Asian/Pacific Islander category, why East Africans are not a genetic mix of African/Caucasian, and I thought as well that the Asian influences in Madagascar are well known, along with the obvious African components. Cannot the same criticisms be made of other studies, such as those from the Rosenberg and Risch labs? Even if a limited number of population groups are used to look at variation, for most populations, useful information can be obtained.
In summary, I really don’t see major problems with the tests, when properly interpreted. As well, newer tests are being devised. Just because the tests may be misused and the data twisted to fit political objectives, this does not invalidate the tests themselves.
I see the major points as being that the tests are relative and comparative, rather than absolute, and that the names given to genetic ancestral categories do not exactly correlate with the specific ethnic/racial groups they are named after. For example, some people seem to be disturbed that tested Irish were found to have a certain low percentage of “Middle Eastern” and “South Asian” affiliations.
Assuming these are above statistical significance, then, how can that be?? – after all, the Irish are NW Europeans with no history of being “invaded by Arabs or South Asians.” But, that’s the point, the data are NOT saying that there must be direct descent from those particular groups. Instead what the data simply show is that the predominant distinctive genetic (ancestral) components in Middle Easterners and South Asians are also found as minor components in the gene-pool of the Irish. Why is not known, but it does not logically require direct descent from one group into another - simply a sharing of allele frequencies.
That is, admittedly, not genealogy. But as I’ve said, these are not really genealogy tests. Rather, they are tests of relative racial/genetic affiliation. The data, and in particular the minority affiliations, are NOT randomly scattered among individuals and groups - as they would be if they had no relevance. They are structured in a manner consistent with broad racial clines and historical trends (eg, elevated Middle Eastern in Ashkenazim) and they correlate with phenotype, too.
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