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In the past decade, genetic testing aimed at identifying ancestry has experienced exponential growth, with nearly 26 million tests sold since 2018 (6). Companies – such as 23andMe – offer kits to trace your genetic legacy and geographical origins using Y-chromosome, mitochondrial, and whole-genome markers (1). Genetic ancestry testing holds the potential to identify the geographic origins of an individual’s ancestors, ancestral lineages, and relatives, but does not define a deterministic cultural identity.
DNA located in the mitochondrion, mtDNA, is inherited maternally in both sexes and can thus provide evidence of an direct, unbroken female lineage (10). The mtDNA typically passes unchanged from mother to offspring, except in the rare case of a mutation. By comparing full mtDNA sequence or assaying for particular haplogroups, it is possible to establish both close ancestry and rough global origins, respectively (4). Regardless, two individuals, even with an exact mtDNA match, may have had an ancestor as far back as ten or sixteen generations (9). Consumers should thus be warned against over-interpreting mtDNA results since they unravel a single thread in an individual’s genetic ancestry. A distinct benefit of mtDNA tests is the ability to distinguish maternal lineage in recorded genealogical data in which females adopt the male surname (10).
Contrary to mtDNA, Y-chromosome DNA is inherited paternally, passed down from father to son. Ancestry tests analyze locations along the Y chromosome, cataloging mutations known as single nucleotide polymorphisms and repeating patterns known as short tandem repeats (8). Test results can determine if two male members of separate families with the same surname have a close genetic relationship (10). In addition, a multitude of haplogroups, representing branching in the Y-chromosome tree, can be used to examine the presence of a common ancestor thousands of years back, contributing another thread to the central question of genetic ancestry (8,7).
A more comprehensive basis of determining ancestry relies on the presence of millions of autosomal variants, such as single nucleotide variants (SNVs), across the genome (10,3,7). An individual’s unique pattern of SNVs is compared with various reference populations and other consumers in order to infer their ancestry (10). Companies such as 23andMe provide a readout of broad ancestry and specific subgroups. Ancestral populations such as European and Western Asian are often further broken down into subpopulations (e.g. British, Greek, Iran). The accuracy of more specific statistical inferences is often variable, with companies examining different SNVs reporting inconsistencies in percentages for the same individual (3). In addition, since many reference populations do not account for migration and interbreeding thousands of years back, an ethnicity estimate with a high degree of confidence could still differ drastically from an individual’s expectations (10). Statistical inferences have diminished accuracy in regions such as East Africa and South Asia with comparatively limited data relative to well studied European populations, leading to further possible inconsistencies (7).
While the commercialization of genetic-ancestry tests has resulted in improved accuracy and innovation, the hyper-aggressive marketing of such products risks misinforming consumers, particularly in regards to cultural heritage. Consider, for example, an advertisement by the company Ancestry where a woman finds “[her] strength” after realizing she shares maternal lineage to a matriarchal people in Ghana (11). The pervasive marketing has even infiltrated music: In 2018, Spotify and Ancestry partnered to suggest playlists and artists based on test results, blatantly equating DNA and cultural heritage (2). While such marketing efforts are externally harmless, they carry a hidden message that DNA plays a meaningful role in our cultural identity. Most consumers are ill-informed in the field of genomic science, and may assume that their test results are deterministic and connote a contribution to heritage.
Genetic-ancestry tests may also perpetuate the idea of innate racial differences and entangle race with culture. A randomized trial reported that White Americans with lower genetic literacy had increased essentialist views after receiving test results (6). Those of Hispanic heritage share cultural aspects such as language, but may differ in genetic test results due to post-colonial admixture of Native, European, and African populations (5). Does a test result of 90% European heritage indicate “more” Hispanic heritage than 80% African? Such conclusions are entirely inaccurate and dangerous, but plausible given the genetic literacy of the typical consumer.
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