Ancient DNA data are consumed by people largely untrained in genetics, embedded in a culture excited about the possibilities of personalized medicine and captivated by recreational DTC genomics. The Human Genome Project was completed in 2003 and it was supposed to usher in a healthcare revolution in which we would all benefit from personalized medicine tailored to the specifics of our individual genomes.6 While the tangible health benefits flowing from genome sequencing have been few and far between, the public enthusiasm for genetic data has shown no sign of abating.
One of the largest DTC recreational genomics companies, 23andMe, was founded only three years after the completion of the Human Genome Project. It was followed by Ancestry DNA in 2012. By 2018, the global market value for DTC genomics reached US $830 million, and it is anticipated that by 2025, the global DTC genomics market will value more than US $2.5 billion.7 People spit in tubes and hand over money because of a perception that the results they obtain from these companies are meaningful. As Daniel Strand and Anna Källén observe in the introduction to this volume, the popular discourse on DNA has long reproduced the assumption that our genes offer a source of truth about who we “really” are. So pervasive is the notion that our essential selves are to be found in our DNA that is has become a metaphor for realness—characteristic X is “baked into our DNA.” In a way, this idea also comes to the fore in Amade M’charek’s chapter about the changing representations of the Neanderthal: as soon as it is proved that modern humans share DNA with Neanderthals, this hominin group ceases to be portrayed as a monkey or a troglodyte and is instead depicted as “one of us.”
The meteoric rise of DTC companies and their broad uptake by the general public for both ancestry estimation and detection of health-related variants exacerbate a tendency toward genetic determinist thinking that is planted in peoples’ thinking in high school biology classes about Gregor Mendel. You could be forgiven for thinking that we are quite good at examining DNA sequences and predicting important phenotypic traits. We use human characteristics to teach Mendelian inheritance in both high school and at the university. We teach that, for example, the ability to roll your tongue is dominant over the inability, and so if you have TT or Tt combinations of alleles you will be able to roll your tongue and will be unable to roll your tongue only if you have tt alleles. We further teach that if two tongue rolling Tt people have children, about a quarter of their kids will be tt and thus unable to roll their tongues. Unfortunately for this favorite of the classroom, tongue rolling ability does not work like that at all. Instead, it is likely influenced by multiple genes, and there is probably a significant environmental influence as well.8
The nongenetic component of tongue rolling ability points to the fact that the actions of genes are influenced by the environments in which they find themselves; but further, the actions of genes are impacted by the genomes in which they find themselves. To illustrate this point, consider another favorite of the classroom, which is indeed inherited in a Mendelian fashion: the ABO blood system. At the end of the long arm of chromosome 9 is a gene which encodes an enzyme that comes in three alleles.9 If the A allele is present, a sugar called N-acetylgalactosamine is added as a fifth sugar on the surface of the red blood cell. If the B allele is present, then the sugar galactose is added to the existing string of four sugars. The O allele is nonfunctional, and so does nothing. Thus, if you have inherited an O allele from each of your parents, you have no fifth sugar on any of your red blood cells and have type O blood. When considered in this way, it is then easy to see both why A and B alleles are dominant to O, and why A and B alleles are co-dominant to each other.
Genes do not, however, act is isolation. They act in functional biological organisms, as part of nested physiological pathways. There is another gene, on the long arm of chromosome 19, which is relevant to a person’s ABO status. This gene (FUT1) similarly encodes an enzyme which moves sugars around.10 In most people, the enzyme encoded by FUT1 adds the sugar fucose to a string of three sugars on red blood cells. In people who inherited the recessive, nonfunctional version of this gene (genotype hh), that sugar is never added. People carrying this combination of alleles have what is known as the Bombay phenotype. It does not matter what alleles are carried at the ABO gene, because those enzymes have no substrate upon which to act. Regardless of the alleles carried at ABO, a person with the Bombay phenotype will have functionally O-type blood.11 There are no reported health effects associated with the Bombay phenotype, until someone needs a blood transfusion. Transfused with typical O-type blood with red blood cells with four sugars on their surfaces, the alleles of the ABO system suddenly have a task they can complete, and add fifth sugars to the newly transfused red blood cells. The patient’s system now recognizing the transfused blood as nonself launches an aggressive immune response.12
The ABO system, then, is a very straightforward Mendelian system. Except when it is not. Genes are obviously important in the building of bodies, but the relationships between genes and traits are not simple or unidirectional and almost never involve single genes and single characteristics. We know much more about the genetics of disorder than we do about the genetics of the average, so genetic disease is a useful place to think about the relationships between genotype and phenotype. Of the diseases we know to show patterns of inheritance, only about 2 percent show patterns consistent with simple Mendelian inheritance.13 The rest are influenced by many genes interacting in complex reticulated networks with each other and with other contributors to the developmental system, including the environment and nongenetic inheritance.14 Their influence is probabilistic, not deterministic.
Final Thoughts
Despite grandiose claims to the contrary, aDNA data have not, and will not, revolutionize reconstructions of the past. Certainly, there has been a dramatic increase in the volume of genetic data relevant to reconstructions of prehistory, but our powers of interpretation have lagged behind the truly impressive improvements in laboratory-based techniques for DNA recovery and analysis.
Further, genetic data are meaningful only to the extent to which they articulate with other kinds of data, which means that engagement across specialties has to be careful, equitable, and undertaken with a humility about the boundaries of one’s own knowledge and a respect for the epistemological rigor in diverse disciplines. As suggested by Stewart B. Koyiyumptewa and Chip Colwell’s chapter about the conflicts between paleogeneticists and Indigenous groups in the United States, a productive future for aDNA research hinges on an engagement with descendant communities and their inclusion as core members of research teams, drivers of research agendas, and lead investigators.
Finally, the field of aDNA studies would benefit enormously from a recalibration of its core mission and its core values. If the research community is interested in accurate, nuanced, and rich reconstructions of the past, we need to stop reaching for the flashy press release, slow down, and truly grapple with the intricacies of synthesizing multiple, complex datasets. As made clear in Marianne Sommer and Ruth Amstutz’s chapter about the graphic representations employed in aDNA research, complex historical processes must not be reduced to simple figures or models.
As this volume has shown, it is simultaneously true that the revolutionary nature of aDNA research for the reconstruction of prehistory has been overblown and that aDNA can contribute meaningfully to our understandings of the past. The contributors to this volume are largely not practitioners of aDNA research. The book is generally critical of aDNA research as it is currently practiced, even when the authors are primary producers of aDNA data. Nonetheless, the contributors herein engage with the field because, done carefully, slowly, with respect for ancestors, with respect for descendant communities, and with care for complexities of social science data, the discipline can contribute significantly to the work of prehistorians. Ancient DNA research will be greatly enriched if the scholars at the bench take seriously the work done by the authors of Critical Perspectives on Ancient DNA.
Notes
1. I strongly prefer “molecular anthropologist” over “anthropological geneticist” for the kinds of researchers I’m talking about because they are primarily anthropologists with a molecular toolkit rather than geneticists who happen to focus on humans. Thus, for a molecular anthropologist, anthropology is the core, not the modifier. My perspective on this point is not widely shared, and many researchers who earned PhDs in anthropology, hold positions in departments of anthropology, and address anthropological questions with molecular data call themselves anthropological geneticists.
2. Ancient DNA data can also be generated from paleontological remains that do not derive from archaeological contexts, but this volume focuses on archaeological contexts and questions.
3. See Carol E. Cleland, “Methodological and Epistemic Differences between Historical Science and Experimental Science,” Philosophy of Science 69, no. 3 (2002): 474–496.
4. See K. Ann Horsburgh, “Molecular Anthropology: The Judicial Use of Genetic Data in Archaeology,” Journal of Archaeological Science 56 (2015): 141–145.
5. David Reich, Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past (Oxford: Oxford University Press, 2018), xx.
6. See Francis Collins and David Galas, “A New Five-Year Plan for the US Human Genome Project,” Science 262, no. 5130 (1993): 43–46.
7. National Academies of Sciences, Engineering, and Medicine, Exploring the Current Landscape of Consumer Genomics: Proceedings of a Workshop (Washington, DC: National Academies Press, 2020), 11.
8. See John J. Reedy, Thomas Szczes, and Thomas D. Downs, “Tongue Rolling among Twins,” Journal of Heredity 62, no. 2 (1971): 125–127; Nicholas G. Martin, “No Evidence for a Genetic Basis of Tongue Rolling or Hand Clasping,” Journal of Heredity 66, no. 3 (1975): 179–180; Taku Komai, “Notes on Lingual Gymnastics: Frequency of Tongue Rollers and Pedigrees of Tied Tongues in Japan,” Journal of Heredity 42, no. 6 (1951): 293–297; Alfred Henry Sturtevant, A History of Genetics (New York: Harper & Row, 1965). It is also worth noting that teaching genetics in this way, with fundamental errors in facts, is an effective way to lead high school and undergraduate students to suspect that their social father is not their biological father; a phenomenon we euphemize as a “nonpaternity event.” Regardless of what we call it, leading teenagers to doubt the identities of their biological fathers is a terrible thing to do to people, and it is an especially terrible thing to do based on bad biological information. For a discussion about this, see John McDonald, Myths of Human Genetics (Baltimore, MD: Sparky House, 2011).
9. See Marion E. Reid and Christine Lomas-Francis, The Blood Group Antigen FactsBook (New York: Elsevier Academic, 2004).
10. See Yoshiro Koda et al., “Missense Mutation of FUT1 and Deletion of FUT2 Are Responsible for Indian Bombay Phenotype of ABO Blood Group System,” Biochemical and Biophysical Research Communications 238, no. 1 (1997): 21–25; R. J. Kelly et al., “Molecular Basis for H Blood Group Deficiency in Bombay (Oh) and Para-Bombay Individuals,” Proceedings of the National Academy of Sciences 91, no. 113 (1994): 5843–5847; Florence F. Wagner and Willy A. Flegel, “Polymorphism of the h Allele and the Population Frequency of Sporadic Nonfunctional Alleles,” Transfusion 37, no. 3 (1997): 284–290.
11. See Reid and Lomas-Francis, Blood Group Antigen FactsBook.
12. See Sheetal Malhotra et al., “Acute Hemolytic Transfusion Reaction in a Patient with Bombay Phenotype: Implications for ABO Grouping,” Indian Journal of Hematology and Blood Transfusion 30 (2014): 108–110.
13. See Eva Jablonka and Marion J. Lamb, Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life (Cambridge, MA: MIT Press, 2006).
14. See James DiFrisco and Johannes Jaeger, “Beyond Networks: Mechanism and Process in Evo-devo,” Biology and Philosophy 34 (2019): 1–24.
Bibliography
Abu El-Haj, Nadia. “The Genetic Reinscription of Race.” Annual Review of Anthropology 36 (2007): 283–300.
Adichie, Chimamanda Ngozi. “The Danger of a Single Story.” Ted Talk, July 2009. https://www.ted.com/talks/chimamanda_ngozi_adichie_the_danger_of_a_single_story#t-1796.
Ahmed, Sara. The Cultural Politics of Emotion. Edinburgh: University of Edinburgh Press, 2004.
Alexander, David H., John Novembre, and Kenneth Lange. “Fast Model-Based Estimation of Ancestry in Unrelated Individuals.” Genome Research 19, no. 9 (2009): 1655–1664.
Alpaslan-Roodenberg, Songül, David Anthony, Hiba Babiker, Eszter Bánffy, Thomas Booth, Patricia Capone, Arati Deshpande-Mukherjee, et al. “Ethics of DNA Research on Human Remains: Five Globally Applicable Guidelines.” Nature 599, no. 7883 (2021): 41–46.
“Altmetric Attention Score.” Altmetric, December 28, 2022. https://wiley.altmetric.com/details/24937638.
“Anthrax Outbreak Infects Nomads in Siberia.” Deutsche Welle, August 2, 2016. https://www.dw.com/en/anthrax-outbreak-infects-nomads-in-siberia/a-19444460.
Appleby, Jo, Guy N. Rutty, Sarah V. Hainsworth, Robert C. Woosnam-Savage, Bruno Morgan, Alison Brough, Richard W. Earp et al. “Perimortem Trauma in King Richard III: A Skeletal Analysis.” Lancet 385, no. 9964 (2015): 253–259.
Appleby, Jo, Piers D. Mitchell, Claire Robinson, Alison Brough, Guy Rutty, Russell A. Harris, David Thompson, and Bruno Morgan. “The Scoliosis of Richard III, Last Plantagenet King of England: Diagnosis and Clinical Significance.” Lancet 383, no. 9932 (2014): 1944.
Arning, Nicolas, and Daniel J. Wilson. “The Past, Present and Future of Ancient Bacterial DNA.” Microbial Genomics 6, no. 7 (2020): 1–19.
“As Earth Warms, the Diseases that May Lie within Permafrost Become a Bigger Worry.” Scientific American, November 1, 2016. https://www.scientificamerican.com/article/as-earth-warms-the-diseases-that-may-lie-within-permafrost-become-a-bigger-worry.
Association for the Advancement of Science (AAAS). “Ancient DNA Reveals Genetic History of China.” EurekAlert!, May 14, 2020. https://www.eurekalert.org/news-releases/708044.
“The Atlas: News and Publications.” Atlas Project. https://web.archive.org/web/20211013183529/http://theatlas.se.
