Genetic testing is the use of DNA information of an individual to make links about the ancestry of an individual in the past thousands of years. On the other hand, genetic genealogy involves a combination of both the DNA information and the historical records to make a broader match in the ancestry of an individual ( Royal et al., 2010 ). There has been a lot of uncertainties surrounding the ancestry testing given that many people claim to receive ancestry information that they believe is not accurate or does not reflect their true ancestral background. Several companies have been reported to offer individual generic ancestry tests, but the results of these have shown a lot of variations in the interpretation raising several uncertainties. First, the concept of ancestry has come out to create a lot of misunderstandings amongst scientists as well as the community in general. This has further formed a lot of uncertainties as people are unable to identify with their true ancestral links even after undergoing tests while others get the information they believe is inaccurate.
Scientists have had problems in trying to sort out definitive answers concerning the ancient migrations and the geographic origins. This means that ancestry testing rely much on the use of more substantial and more statistically weighty samples instead of the exact data from the individuals and this could lead to uncertainty in the outcome of the tests. At the same time, studies have shown that only 1100 genetic samples exist, meaning that generic ancestry test on itself is still far much from being considered conclusive ( Royal et al., 2010 ). Many people expect that the generic ancestry tests would help them understand their ancestral origin far into thousands of years ago. However, science has not been precise on this issue as the ancestral geographical roots rely on the broader ancestral population rather than a specific origin. For example, the ancestry tests would show that one is from North America, Asia, Africa or Europe. Studies have shown that these genetic groupings have been based on just estimates of the original population due to lack of ability to make samples of the ancestral population. This can sometimes lead to tests showing no family tie even if one hails from a given section of the map due to the use of proxy population.
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Another uncertainty that has existed in the ancestry tests is the different interpretations and analysis of the results which greatly vary depending on the test method used. The various test methods can include mtDNA and Y chromosome markers. These different interpretation have led to people getting different results in different ways thus raising confusion on their exact ancestral origins. While scanning for the haploid genetic markers may show the existence of common paternal ancestry, these only represent a smaller fraction of an individual’s genetic ancestry, and therefore the results may not be accurate. Even though the use of autosomal markers for scanning could represent a higher fraction of the genome, there is still the limitation of missing ancestral code ( Duster, 2016 ). This according to studies is because the more distance the ancestors go, the higher the rate of decrease in the genetic odds. This further makes it difficult to make precision on the exact ancestral origin of an individual leaving room for only broader generalization in the map.
The use of the Y chromosome as a test method only gives the information about an individual’s male ancestry. While only males carry the Y chromosomes, the females can always learn from the lineage of the father or even brother. A lot of variation, however, exist on the kind of information that is given on this. The haploid markers mutate at different rates which lead to the provision of information at different times. The type of information an individual receives depends heavily on the number of markers tested and from which type of the chromosome. The resulting information of the test will, therefore, vary depending on whether SNP or STR tests were used because each will give different information on an individual’s ancestry. At the same time, the information that is provided about the deep ancestry of an individual is limited as it is purely based on the prediction of the haplogroup assignment. Whenever two people have the same Y-DNA, the test will show that they have the same ancestor even if it may be several years ago ( Duster, 2016 ). Uncertainty arises when that specific time cannot be arrived at precisely but rather to rely on mere estimates which may not be accurate. Therefore, even if two people may test to share a common ancestor, they may be unable to know the exact time for their ancestry origin. A lot of information on the ancestry tests still rely on estimates with limited precision thus creating a lot of uncertainties.
The results of the ancestry tests are always accompanied by the origin of the ancestry including the map and parts of the world where they migrated. However, uncertainties arise due to difficulty in ascertaining the exact place where these ancestors originated and the way they spread. An ancestry test may reveal that ancestors originated from West Africa, but it is difficult to tell where precisely in West Africa did they originate. There is, therefore, lack of specification on the exact place the ancestors originated because only a broad geographical coverage in the map is provided by the test living individuals still uncertain of the exact ancestral origins ( Fujimura & Rajagopalan, 2011 ).
The mtDNA test only gives the information about the female lineage which can be passed to the next generation but only through the female. This test only provides information about one genealogy; from mother to grandmother all the way back to time. Studies have shown that mutation takes place at a rapid rate, and the distribution of the mtDNA is rapid ( Duster, 2016 ). It is therefore difficult to provide a precise inference into the far past. At the same time, like in the Y-chromosomes, it is difficult for one to know the exact migration location in the map for the ancestors as it is merely based on estimates. As one goes back into the deeper past, there is a diminishing mtDNA fraction of the total ancestry, and the tests results may not give a precise ancestry connection into the far past. This has led to individuals getting ancestry tests results which they doubt. For instance, at a time when one expects to have an ancestral origin from central Europe, the test may reveal that the person has originated from northern Europe due to diminishing mtDNA as one goes far much into the future. The uncertainty is therefore that the accuracy and precision of the ancestry test using mtDNA depends on the past time in the ancestry lineage.
The use of the autosomal test method tends to cover most of the DNA sequence and genes which could give a more detailed ancestry lineage. The haploid markers are capable of providing the ancestry information more precisely in the most recent generations ( Bolnick et al., 2018 ). However, as one moves to several generations backward, it becomes difficult to provide precise and accurate ancestry lineage because only a smaller proportion of the DNA is covered. This is because the inheritance of the DNA diminishes as generations increases and if one had an ancestor born over 400 years ago, it is most likely that no DNA was inherited from him. This, therefore, means that autosomal test is only useful in the recent past, but as one goes into the many past generations, the results become merely speculative with no any precision.
There has been no uniformity in the test results from different companies as people have received different results from different companies. This is probably because different companies apply different test methods and databases. This has been confusing to individuals who get contradicting ancestry information from different companies. There is a lot of uncertainty about the way results are analyzed and interpreted, and this has led to different conclusions. Whichever the test method used and method of analysis used, the results ought to have been the same. The margin of error and statistical uncertainty are usually taken care of in any scientific tests. However, in the ancestry tests, what matters is the interpretation of the results because this is what will affect how individuals perceive effects.
In conclusion, ancestry tests still have many uncertainties that need to be clear if the whole process is to yield trustworthy results. The fact that most test methods used may not give precise ancestry lineage into many past generations means that most results are merely speculative with no statistical evidence. Also, the estimates of the geographical origin are based on generalization on the map rather than a precise location due to inability to sample the exact ancestral population. The various test methods can also produce results with varied analysis and interpretation, and this has led to confusion. Most scanning is done for the genetic markers also represent only a smaller fraction of the total genes in the ancestry lineage because DNA diminishes with more generations backward. This makes it difficult to match an individual ancestry that dates back into more than 400 years ago.
References
Bolnick, D. A., Fullwiley, D., Duster, T., Cooper, R. S., Fujimura, J. H., Kahn, J., ...& Ossorio, P. (2018). 48. The Science and Business of Genetic Ancestry Testing. Beyond Bioethics: Toward a New Biopolitics , 422.
Duster, T. (2016). Ancestry Testing and DNA: Uses, Limits–and Caveat Emptor. In Genetics as Social Practice (pp. 75-88). Routledge.
Fujimura, J. H., & Rajagopalan, R. (2011). Different differences: The use of ‘genetic ancestry’versus race in biomedical human genetic research. Social Studies of Science , 41 (1), 5-30.
Royal, C. D., Novembre, J., Fullerton, S. M., Goldstein, D. B., Long, J. C., Bamshad, M. J., & Clark, A. G. (2010). Inferring genetic ancestry: opportunities, challenges, and implications. The American Journal of Human Genetics , 86 (5), 661-673.
