Källén opens with some background. In late 1989, Erika Hagelberg and colleagues established something once considered impossible: the extraction and analysis of DNA from dry bone (pig). Their feat promised tremendous potential for archeology; however, the expense and complexity of sequencing ancient DNA (aDNA) meant that the field of archeogenetics had to wait until computerized techniques allowed for high throughput methods.

Next Källén offers a lucid description of DNA, and its various forms used in the context of tracing ancestry and understanding inheritance–Y chromosome (from fathers) and mitochondrial (from mothers)—and how it contributes well to forensic science today. But, she points out, the molecule deteriorates with time and only fragments remain to be recovered with difficulty. Scientists must turn to computerized probabilities that rely on similar aDNA examples to select likely genetic candidates for filling in the gaps.

Källén’s beef is mostly with what popular media makes of the aDNA results that are expressed more cautiously by the scientists themselves. She skewers the ecstatic 2017 reporting that a Viking warrior, buried with armour and weapons, had been proven by aDNA to be a woman–something that was already known through anatomical examination when her grave was uncovered in 1878. But she also challenges the interpretive biases of researchers who inevitably perceive their findings through a contemporary lens, one that contends with the population biases of present-day genomics.

Among the interpretive leaps can be found the desire to turn aDNA similarities in scant, disparate material into a new and separate “people.” For example, aDNA similarities in a few teeth and a piece of finger, found in only two widely separated places, have become the Denisovian “people.” A newfound furor for facial reconstruction has recruited aDNA to serve “the look” of this almost imaginary Denisovian “species.” Likewise, for the 10,000 year-old Cheddar man whose skull offered architecture, aDNA was to provide his (blue) eyes and (dark) skin colour.

Geographic variations of comparable aDNA findings with differing chronological tags become mass migrations, displayed by arrows crossing vast swaths of territory. When aDNA results are picked up by ethno-nationalist agendas, these pressures revive long-discredited forms of entitlement and racism.

In some examples, DNA findings must be contorted to match what was already settled from documentary and oral traditions: for example, the effort to match the DNA extracted from the braid of the leader Sitting Bull to that of his great-grandson. In a few generations, so much mixing has occurred that the common elements were few. In the end, the relationship was not being tested; it was aDNA’s ability to confirm it that wobbled.

Perhaps Källén’s greatest caution comes in her warning that the molecular signature of DNA is not identity as much as we would like it to be, nor does it reveal culture and “paleopersonalities.” She describes how commercial entities promising to uncover our origins do so on probabilities based on frequencies of myriad DNA variations. She also wonders about our insecurities that foster such a market.

In the end, aDNA is not a revolution. It is just a molecule and a useful adjunct to the methods we already possess, not the least of which is its ability to give us new questions.

The Trouble with Ancient DNA: Telling Stories of the Past with Genomic Science
Anna Källén
University of Chicago Press, 2025. 160 pages

Image of Cheddar Man from Wikicommons