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How accurate is the AncestrybyDNA™ test?

The AncestrybyDNA™ test provides your ancestral proportions based on years of collaborative research of populations representing the four ancestral groups. This research identified 176 informative markers in our DNA, called Ancestry Informative Markers (AIMs).The scientists who developed this test have determined the frequency of DNA sequence variants (DNA markers) in the various human populations, and by determining your unique sequence at these points in your DNA; we can determine the probability that you identify with each of the 4 groups.

The AncestrybyDNA™ test results give you a 95% confidence interval, which is a measure of the statistical strength of the test. The only way to achieve 100% accuracy in an ancestry test would be to go back in time and test each and every one of your ancestors. Since this is impossible, we rely on statistics to make a prediction of your most likely ancestry mix.

The scientists who developed the AncestrybyDNA™ test have conducted extensive validation studies with various numbers of markers to create a test that was economically feasible as well as provides the most robust statistical data. The first version of the test used 71 markers—today we test 176 markers to obtain a much higher confidence level while keeping costs to a minimum.

The test has been evaluated using a large number of people from a wide range of ancestral groups, and the estimates correspond well to what is known from anthropological and historical data. For example, Hispanics are known to have arisen as an ethnic group from the blending of colonial Europeans with Indigenous Americans, and the hundreds of Hispanics we have tested align with these two groups almost exclusively, as expected. As another example, though most Nigerians’ results indicate unmixed African BioGeographical Ancestry (BGA), African Americans show more of a mixture between this group and Europeans, which is also what would be expected from what we know about the admixture between Africans and Europeans in the United States.

The method has also been validated through pedigree challenge; when the BGA is determined from a mother and father, that of their children should plot somewhere between the two. To date, we have tested numerous family pedigrees, and the ancestral proportions of offspring always plot somewhere amongs those of their parents. When outside agencies blindly test the MLE estimates, they prove to be excellent estimates of ancestral proportions.

For further information about these tests, please consult the following published literature:

1. Frudakis, Tony. Molecular Photofitting: Predicting Ancestry and Phenotype Using DNA. 2008. Burlington, MA: Academic Press

2. Parra, E., Marcini, A., Akey, J., Martinson, J., Batzer, M., Cooper, R., Forrester, T., Allison, D., Deka, R., Ferrell, R. and M. Shriver. 1998. Estimating African American Admixture Proportions by Use of Population Specific Alleles.Am. J. Hum. Genet. 63:1839-1851.

3. Pfaff, C., Parra, E., Bonilla, C., Hiester, K., McKeigue, P., Kamboh, M., Hutchinson, R., Ferrell, R., Boerwinkle, E., and M. Shriver.2001. Population Structure in Admixed Populations: Effect of Admixture Dynamics on the Pattern of Linkage Disequilibrium.Am. J. Hum. Genet. 68:198-207.

4. Parra, E., Kittles, R., Argyropoulos, G., Pfaff, C., Hiester, K., Bonilla, C., Sylvester, N., Parrish-Gause, C., Garvey, W., Jin, L., McKeigue, P., Kamboh, M., Ferrell, R., Pollitzer, W., and M. Shriver.2001. Ancestral Proportions and Admixture Dynamics in Geographically Defined African Americans Living in South Carolina.American Journal of Physical Anthropology 114:18-29.

5. Frudakis, T., V Kondragunta, M Thomas, Z Gaskin, S Ginjupalli, S Gunturi, V Ponnuswamy, S Natarajan, and P Nachimuthu. 2003. A Classifier for SNP-Based Inference of Ancestry. Journal of Forensics Sciences. 48(4):771-82.